Dissertations / Theses on the topic 'Pathogenicity genes'
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Reitmann, Anandi. "Identification of pathogenicity genes in Phytophthora cinnamomi." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/79179.
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Nishiyama, Yukihiro. "Herpesvirus Genes: Molecular Basis of Viral Replication and Pathogenicity." 名古屋大学医学部, 1996. http://hdl.handle.net/2237/6180.
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Holman, Holly A. "Investigation of ICP34.5 and its role in HSV pathogenicity." Thesis, University of Glasgow, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321914.
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Fulton, Ciaran Eugene. "The isolation of virulence genes from the ubiquitous plant pathogen, Colletotrichum gloeosporioides." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337296.
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Jackson, Robert Wilson. "Plasmids and virulence in Pseudomonas syringae pv. phaseolicola." Thesis, University of the West of England, Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389510.
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Liddle, Shona. "Strategies for studying pathogenicity genes of Xanthomanas campestris pv. campestris." Thesis, University of East Anglia, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306113.
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Besi, Maria. "Identification of novel pathogenicity-related genes in the rice blast fungus, Magnaporthe oryzae." Thesis, University of East Anglia, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.539361.
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Couchman, Edward C., Hilary P. Browne, Matt Dunn, Trevor D. Lawley, J. Glenn Songer, Val Hall, Liljana Petrovska, et al. "Clostridium sordellii genome analysis reveals plasmid localized toxin genes encoded within pathogenicity loci." BioMed Central Ltd, 2015. http://hdl.handle.net/10150/610282.
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BACKGROUND: Clostridium sordellii can cause severe infections in animals and humans, the latter associated with trauma, toxic shock and often-fatal gynaecological infections. Strains can produce two large clostridial cytotoxins (LCCs), TcsL and TcsH, related to those produced by Clostridium difficile, Clostridium novyi and Clostridium perfringens, but the genetic basis of toxin production remains uncharacterised. RESULTS: Phylogenetic analysis of the genome sequences of 44 strains isolated from human and animal infections in the UK, US and Australia placed the species into four clades. Although all strains originated from animal or clinical disease, only 5 strains contained LCC genes: 4 strains contain tcsL alone and one strain contains tcsL and tcsH. Four toxin-positive strains were found within one clade. Where present, tcsL and tcsH were localised in a pathogenicity locus, similar to but distinct from that present in C. difficile. In contrast to C. difficile, where the LCCs are chromosomally localised, the C. sordellii tcsL and tcsH genes are localised on plasmids. Our data suggest gain and loss of entire toxigenic plasmids in addition to horizontal transfer of the pathogenicity locus. A high quality, annotated sequence of ATCC9714 reveals many putative virulence factors including neuraminidase, phospholipase C and the cholesterol-dependent cytolysin sordellilysin that are highly conserved between all strains studied. CONCLUSIONS: Genome analysis of C. sordellii reveals that the LCCs, the major virulence factors, are localised on plasmids. Many strains do not contain the LCC genes; it is probable that in several of these cases the plasmid has been lost upon laboratory subculture. Our data are consistent with LCCs being the primary virulence factors in the majority of infections, but LCC-negative strains may precipitate certain categories of infection. A high quality genome sequence reveals putative virulence factors whose role in virulence can be investigated.
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Ammouneh, Hassan. "Molecular characterisation of virulence genes on a pathogenicity island in Pseudomonas savastanoi pv. phaseolicola." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405032.
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Gamieldien, Junaid. "Novel genomic approaches for the identification of virulence genes and drug targets in pathogenic bacteria." Thesis, University of the Western Cape, 2001. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_4400_1185438906.
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While the many completely sequenced genomes of bacterial pathogens contain all the determinants of the host-pathogen interaction, and also every possible drug target and recombinant vaccine candidate, computational tools for selecting suitable candidates for further experimental analyses are limited to date. The overall objective of my PhD project was to attempt to design reusable systems that employ the two most important features of bacterial evolution, horizontal gene transfer and adaptive mutation, for the identification of potentially novel virulence-associated factors and possible drug targets. In this dissertation, I report the development of two novel technologies that uncover novel virulence-associated factors and mechanisms employed by bacterial pathogens to effectively inhabit the host niche. More importantly, I illustrate that these technologies may present a reliable starting point for the development of screens for novel drug targets and vaccine candidates, significantly reducing the time for the development of novel therapeutic strategies. Our initial analyses of proteins predicted from the preliminary genomic sequences released by the Sanger Center indicated that a significant number appeared to be more similar to eukaryotic proteins than to their bacterial orthologs. In order determine whether acquisition of genetic material from eukaryotes has played a role in the evolution of pathogenic bacteria, we developed a system that detects genes in a bacterial genome that have been acquired by interkingdom horizontal gene transfer.. Initially, 19 eukaryotic genes were identified in the genome of Mycobacterium tuberculosis of which 2 were later found in the genome of Pseudomonas aeruginosa, along with two novel eukaryotic genes.
Surprisingly, six of the M. tuberculosis genes and all four eukaryotic genes in P. aeruginosa may be involved in modulating the host immune response through altering the steroid balance and the production of pro-inflammatory lipids. We also compared the genome of the H37Rv M. tuberculosis strain to that of the CDC- 1551 strain that was sequenced by TIGR and found that the organisms were virtually identical with respect to their gene content, and hypothesized that the differences in virulence may be due to evolved differences in shared genes, rather than the absence/presence of unique genes. Using this observation as rationale, we developed a system that compares the orthologous gene complements of two strains of a bacterial species and mines for genes that have undergone adaptive evolution as a means to identify possibly novel virulence &ndash
associated genes. By applying this system to the genome sequences of two strains of Helicobacter pylori and Neisseria meningitidis, we identified 41 and 44 genes that are under positive selection in these organisms, respectively. As approximately 50% of the genes encode known or potential virulence factors, the remaining genes may also be implicated in virulence or pathoadaptation. Furthermore, 21 H. pylori genes, none of which are classic virulence factors or associated with a pathogenicity island, were tested for a role in colonization by gene knockout experiments. Of these, 61% were found to be either essential, or involved in effective stomach colonization in a mouse infection model. A significant amount of strong circumstantial and empirical evidence is thus presented that finding genes under positive selection is a reliable method of identifying novel virulence-associated genes and promising leads for drug targets.
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Kim, Kwang Hyung. "Functional Analysis of Secondary Metabolite Biosynthesis-Related Genes in Alternaria brassicicola." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/39452.
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Alternaria brassicicola is a necrotrophic pathogen that causes black spot disease on virtually all cultivated Brassicas, A. brassicicola is renowned for its ability to prodigiously produce secondary metabolites. To test the hypothesis that secondary metabolites produced by A. brassicicola contribute to pathogenicity, we identified seven nonribosomal peptide synthetases (NPSs) and 10 polyketide synthases (PKSs) in the A. brassicicola genome. The phenotype resulting from knockout mutations of each PKS and NPS gene was investigated with an emphasis on discovery of fungal virulence factors. A highly efficient gene disruption method using a short linear double stranded DNA construct with minimal elements was developed, optimized, and used to functionally disrupt all NPS and PKS genes in A. brassicicola. Three NPS and two PKS genes, and one NPS-like gene appeared to be virulence factors based upon reduced lesion development of each mutant on inoculated green cabbage and Arabidopsis compared with the wild-type strain. Furthermore some of the KO mutants exhibited developmental phenotypic changes in pigmentation and conidiogenesis. To further characterize the roles of several genes of interest in A. brassicicola development and pathogenesis, the genes AbNPS2, AbPKS9, and NPS-like tmpL were selected for in-depth functional analysis. We provide substantial evidence that the AbNPS2-associated metabolite is involved in conidial cell wall construction, possibly as an anchor connecting two cell wall layers. We also characterized a biosynthetic gene cluster harboring the AbPKS9 gene and demonstrated that this cluster is responsible for the biosynthesis of depudecin, an inhibitor of histone deacetylases and a minor virulence factor. Finally, we demonstrated that a NPS-like protein named TmpL is involved in a filamentous fungi-specific mechanism for regulating levels of intracellular reactive oxygen species during conidiation and pathogenesis in both plant and animal pathogenic fungi. Collectively our results indicate that small molecule nonribosomal peptides and polyketides in A. brassicicola play diverse, but also fundamental, roles in fungal development and pathogenesis.Ph. D.
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Kgaladi, Joe. "Pathogenicity and immunogenicity of recombinant rabies viruses expressing the Lagos bat virus matrix and glycoprotein genes." Thesis, University of Pretoria, 2015. http://hdl.handle.net/2263/79257.
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Lagos bat virus (LBV) is a phylogroup II lyssavirus exclusively found in Africa. Previous studies have shown that this virus is lethal to mice after intracranial (i.c.) and intramuscular (i.m.) inoculation. Pathogenicity determinants of LBV are yet to be determined. The antigenic composition of LBV differs substantially from that of the rabies virus (RABV) and current rabies vaccines do not provide cross protection against LBV and other phylogroup II lyssaviruses. LBV is associated with Pteropodidae bat species and although no human infections have been reported to date, fatal spill-over into dogs, cats and a mongoose have been reported. To investigate the potential role of the LBV matrix (M) protein and glycoprotein (G) in the pathogenesis, reverse genetics technology was used to construct recombinant viruses. The genes encoding the G protein or the M and G protein of the attenuated RABV strain SPBN were replaced with those of LBV (LBVAFR1999) resulting in SPBN-LBVG and SPBN-LBVM-LBVG, respectively. In addition, to evaluate the immunogenicity of the LBV G, the recombinant RABV SPBNGAS-LBVG-GAS was constructed that contained the LBV G inserted between two mutated RABV G genes (termed GAS).
Multi-step growth curves showed that SPBN, SPBNGAS-GAS-GAS (a recombinant RABV containing three G protein genes) had the highest growth rate followed by SPBN-LBVG and SPBNGAS-LBVG-GAS. While there was no statistically significant difference between the growth rate of these viruses (p>0.05), the growth rate of SPBN-LBVM-LBVG was lower than that of the other viruses, including LBVAFR1999. The single-step growth curves yielded similar results, with SPBNGAS-GAS-GAS, SPBNGAS-LBVG-GAS and SPBN producing the highest titres and SPBN-LBVM-LBVG and LBVAFR1999 again producing the lowest titres. The results from both growth curves indicated that both the M and G protein of LBV control the growth rate of the virus and thereby playing a role in pathogenicity.
All the viruses − with a single exception, viz. SPBNGAS-GAS-GAS − were lethal to mice after i.c. inoculation, although the pathogenicity of SPBNGAS-LBVG-GAS was lower compared to the other recombinant viruses. Mice inoculated with LBV and SPBN-LBVM-LBVG had the highest percentage mortality (100%) and the shortest mean incubation period, while those inoculated with SPBNGAS-LBVG-GAS had the lowest percentage mortality (20%) and the highest incubation period. Following i.m. inoculation, only LBVAFR1999 and SPBN-LBVM-LBVG were lethal to mice, indicating that both the M and G protein of LBV play a role in the pathogenesis of LBV.
Serum from mice inoculated with SPBNGAS-GAS-GAS and RABISIN (a commercial rabies vaccine used for dogs) cross-neutralised RABV and DUVV, while no detectable VNA were observed for LBV and MOKV. These findings emphasise the already known concept that vaccines derived from RABV cross-neutralise against DUVV, but not against LBV and MOKV. Most interestingly, serum collected from mice inoculated i.m. with SPBNGAS-LBVG-GAS cross-neutralised phylogroup I and II [RABV, LBV, Duvenhage virus (DUVV) and Mokola virus (MOKV)] lyssaviruses, indicating that this recombinant virus has a potential to be used for the development of a pan-lyssavirus vaccine.Thesis (PhD)--University of Pretoria, 2015.
Microbiology and Plant pathology
PhD
Unrestricted
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Oliveira, Aline Luísa de. "Relação entre genes plasmidiais e virulência e análise do sistema de secreção tipo 6 em isolados de Escherichia coli patogênica aviária (APEC)." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2015. http://hdl.handle.net/10183/119612.
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Escherichia coli patogênicas aviárias (APEC) causam infecções extraintestinais em aves, que podem ser localizadas ou sistêmicas, denominadas colibacilose. O patotipo de APEC não está definido, mas vários genes de virulência são associados a essas cepas, como os genes plasmidiais iroN, ompT, hlyF, iss e iutA, propostos, em 2008, como preditores da virulência de APEC. Além dos genes de virulência conhecidos, outros fatores podem estar associados à patogenicidade bacteriana, como as maquinarias de secreção protéica denominadas Sistemas de Secreção. O Sistema de Secreção do Tipo 6 (T6SS), descrito em 2006, tem sido associado à virulência de cepas APEC. Este trabalho divide-se em duas partes: a primeira teve como objetivo avaliar a frequência dos genes iroN, ompT, hlyF, iss e iutA em 401 cepas aviárias de E. coli e sua relação com a patogenicidade in vivo dessas cepas. A segunda parte teve como objetivos verificar a frequência de genes componentes do T6SS (clpV, vgrG, icmF e dotU), em uma coleção de 187 cepas APEC; e, em algumas cepas positivas para os genes, verificar a expressão de um fenótipo relacionado ao sistema, bem como a expressão do efetor vgrG e da ATPase do sistema clpV2, além da secreção de proteínas, no meio de cultura e durante contato com células eucarióticas. Os resultados da primeira parte indicam que cepas com dois ou mais dos genes analisados tem maior probabilidade de serem patogênicas do que cepas com apenas um ou nenhum dos genes. Já os da segunda parte mostram que várias cepas apresentaram duas cópias de pelo menos um dos genes testados, e algumas delas apresentaram resistência à predação por D. discoideum. Não foram encontradas diferenças entre a expressão dos genes vgrG (1 e 2) e clpV2 em cultura pura ou em contato com células eucarióticas. Este trabalho apresenta a triagem de genes plasmidiais em uma grande coleção de amostras de Escherichia coli, e a primeira triagem de genes do T6SS em uma coleção de isolados APEC.Avian pathogenic Escherichia coli (APEC) causes extraintestinal infections in birds, which can be localized or systemic, known as colibacillosis. The APEC pathotype is still undefined, but several virulence genes are associated with these strains, as the plasmid-linked genes iroN, ompT, hlyF, iss and iutA, proposed in 2008 as APEC virulence predictors. Besides the known virulence genes, other factors may be associated with bacterial pathogenicity, such as the protein secretion machineries called Secretion Systems. Described in 2006, Type 6 Secretion System (T6SS) has been associated with virulence of APEC strains. This work is divided in two parts: the first aimed to evaluate the frequency of iroN, ompT, hlyF, iss and iutA genes in 401 avian strains of E. coli and its relationship with in vivo pathogenicity of these strains. The second part aimed to verify the frequency of T6SS genes (clpV, vgrG, icmF and dotU) in a collection of 187 APEC strains; and verify, in some positive strains, the expression of a phenotype related to the system, as well as the gene expression of effector vgrG and ATPase clpV2, besides the secretion of proteins into the culture medium and during contact with eukaryotic cells. The results of the first part of this study indicate that isolates harboring two or more of the genes analyzed were most likely to be pathogenic than strains harboring only one or none of the genes. The results of the second part show that several strains harbored two copies of at least one of the genes tested, and some of them were resistant to predation by D. discoideum. No differences were found between the expression of genes vgrG (1 and 2) and clpV2 in pure culture or in contact with eukaryotic cells. This work presents the screening of plasmidial genes in a large collection of Escherichia coli isolates, and the first screening of T6SS genes in a collection of APEC isolates.
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Islam, Kazi Tariqul. "IDENTIFICATION AND CHARACTERIZATIONS OF PATHOGENICITY GENES IN FUSARIUM VIRGULIFORME, THE CAUSAL AGENT OF SOYBEAN SUDDEN DEATH SYNDROME (SDS)." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1103.
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Fusarium virguliforme (Aoki, O’Donnell, Homma & Lattanzi), the causal agent of sudden death syndrome (SDS) of soybean (Glycine max [L.] Merrill), is responsible for major soybean yield losses in North America and South America. Despite the importance of SDS, few agronomic practices have been used to manage SDS successfully. Understanding the pathogen and the mechanisms it uses to cause disease is vital to devise effective disease control strategies. However, our knowledge of the pathogenicity mechanisms used by F. virguliforme is limited. The identification of pathogenic genes will shed light on the molecular basis of the interaction between F.virguliforme and soybean, which may ultimately lead to better management of SDS. Therefore, the studies presented in this thesis were aimed at identifying and characterizing candidate pathogenicity genes in F. virguliforme.To fulfill this objective, 40 candidate pathogenicity genes of F. virguliforme were identified based on a combined approach, which included hands-on literature and database mining, functional genomics as well as transcriptome analyses. From these genes, the FvSNF1gene (a sucrose non-fermenting protein kinase 1 ortholog), the Fvstr1 gene (a striatin protein ortholog) were functionally characterized through a gene knock-out strategy. Targeted disruption of the FvSNF1 locus in wild type F. virguliforme strain reduced virulence significantly on soybean and abolished galactose utilization. In addition, the FvΔSNF1 mutant displayed significant reduction in expression of several CWDEs genes and was defective in colonizing the vascular system of the roots. To identify putative target genes regulated by FvSNF1, transcriptome analyses were performed in the FvSNF1 deletion mutant and in the wild-type. Disruption of FvSNF1 affected the level of transcription of 393 genes and a majority of the genes were involved in carbohydrate metabolism, lignin degradation, and cellular signaling pathway. The disruption of Fvstr1, a striatin ortholog in F. virguliforme, resulted in a complete loss of virulence as well as impaired conidiation, conidiophore development and pigmentation in the fungus. The FvΔstr1 mutant also failed to colonize the vascular tissues of roots of inoculated soybean plants. The results suggest that FvSNF1and Fvstr1 have critical roles in pathogenicity. Another part of the study was to investigate the efficacy of ILeVO®, a succinate dehydrogenase inhibitor fungicide from Bayer CropScience, against F. virguliforme. Our results showed that ILeVO® was very active against F. virguliforme in vitro and was very effective in minimizing F. virguliforme infection thus providing yet another tool to combat SDS.
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Andersson, Robert. "Characterisation of regulatory genes involved in the control of virulence determinants in Erwinia carotovora subsp. carotovora /." Uppsala : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 1999. http://epsilon.slu.se/avh/1999/91-576-5732-7.pdf.
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Betts, Melania Figueroa. "Identification of New Pathogenicity Genes in Magnaporthe Oryzae through the Construction of an Agrobacterium Tumefacines-Mediated Insertion Mutant Library." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194453.
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An understanding of plant pathogen-host interactions is essential to design efficient strategies to control disease in crops. Magnaporthe oryzae, an ascomyceteous fungus and causal agent of rice blast disease, is a model organism to study host-microbe interactions. The overall aim of this dissertation project was to identify genes involved in pathogenicity through the construction and characterization of a random insertional mutagenesis library. In order to saturate the genome with DNA inserts, a collection of >54,000 insertion lines of the M. oryzae strain 70-15 was generated via two transformation methods, PEG/CaCl2 (polyethylene glycol)-mediated protoplast transformation and Agrobacterium tumefaciens-mediated transformation. The first part of this dissertation describes the optimization of both transformation approaches, compares their efficiency and provides a description of the high-throughput processing and phenotypic analysis of the insertion lines. An in vitro appressorium assay of 12,000 T-DNA insertion strains allowed the identification of 135 lines that were classified as morphologically or functionally different than wild-type. Rice infection assays demonstrated that 112 of these strains exhibited defects in pathogenicity.The second part of this dissertation project analyzed the T-DNA integration patterns in a subset of pathogenicity mutants. This section aimed to identify the disrupted genes via recovery of M. oryzae sequences adjacent to the sites of T-DNA insertion. Genomic mapping of 61 T-DNA insertions in pathogenicity mutants via rescuing M. oryzae chromosomal T-DNA flanking sequences using inverse PCR resulted in the identification of 22 conserved hypothetical genes with predicted function, 11 predicted open reading frames without a GenBank significant match, two unannotated regions of the genome assembly and seven intergenic regions. The final part of this dissertation describes the characterization of a M. oryzae pathogenicity mutant that contains a T-DNA insertion in the upstream region of two divergently transcribed genes that encode the vacuolar type-ATPase subunit c`` and the general transcription factor TFIIA subunit γ. Genetic complementation demonstrated the insertion of the T-DNA in the promoter region of the general transcription factor TFIIA subunit γ is responsible for observed defects in conidiation, appressorium morphogenesis, and appressorium function. This is the first report relating the function of TFIIA subunit γ to pathogenicity.
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Mansouri, Saara. "IDENTIFICATIN AND CHARACTERIZATION OF PATHOGENICITY GENES IN FUSARIUM VIRGULIFORME, THE CAUSAL AGENET OF SUDDEN DEATH SYNDROME (SDS) IN SOYBEAN." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/dissertations/573.
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Fusarium virguliforme is a soil-borne pathogen that causes sudden death syndrome (SDS) disease in soybean. SDS is one of the most significant diseases of soybean in the United States. Fungal infection results in root and crown rot as well as SDS typical foliar symptoms including chlorosis, necrosis and complete defoliation. The use of soybean cultivars tolerant to SDS is still the most effective way to overcome the disease. On the other hand, the fungal isolates are known to have varied levels of aggressiveness on soybean indicated by the field and greenhouse experiments. Understanding the pathogen and its defense mechanism is the first step in exploring the pathogen-plant interaction. Therefore, the primary aim of this research was to elucidate the mechanism behind F. virguliforme response to soybean defense mechanisms. We further attempted to identify chromosome length polymorphism among F. virguliforme isolates and characterize the possible relationship to their level of aggressiveness. In order to fulfill the first objective, a series of differentially expressed genes were identified in F. virguliforme in the presence of soybean phytoalexin, glyceollin. The Fvgrx2 gene, a Saccharomyces cerevisiae grx2homologue, was selected for further analysis. This study demonstrates for the first time the identification and characterization of dithiol glutaredoxin gene in F. virguliforme . The role of FvGRX2 in the fungal defense to phytoalexin, glyceollin and induced oxidative burst was also investigated by generating anFvΔgrx2 knockout. In order to establish a link between the fungal karyotype and the level of fungal aggressiveness, the chromosome length polymorphism (CLP) was assessed for twenty-two F. virguliforme isolates exhibiting different levels of aggressiveness on soybean. The findings are instrumental in identifying novel pathogenicity such as the ones involved in phytotoxin production, fungicide resistance and aggressiveness.
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Rojas, Thaís Cabrera Galvão 1980. "Detecção de genes sob seleção positiva em linhagens de Escherichia coli patogênicas para aves (APEC) e para humanos." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317369.
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Orientador: Wanderley Dias da SilveiraTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-21T23:45:44Z (GMT). No. of bitstreams: 1 Rojas_ThaisCabreraGalvao_D.pdf: 2609032 bytes, checksum: 23a0546c76c17eff8087d0160c69308d (MD5) Previous issue date: 2012
Resumo: A bactéria Escherichia coli coloniza o trato intestinal de aves e humanos, de maneira comensal sem causar processos infecciosos. No entanto alguns clones adquiriram fatores de virulência específicos, permitindo o desenvolvimento de diferentes doenças como infecção do trato urinário, diarréia e meningite em humanos e colibacilose em aves. As linhagens que causam doença em aves são tipicamente denominadas APEC (Avian Pathogenic Escherichia coli). Neste trabalho foram sequenciados e anotados os genomas de quatro linhagens APECs (SCI-07, SEPT362, S17 e O8)que, juntamente com mais nove genomas referentes a linhagens de Escherichia coli patogênicas para aves e patogênicas para humanos foram utilizados para a busca de genes sob seleção positiva. Os genes homólogos foram agrupados,e posteriormente submetidos ao alinhamento de códons e das sequencias protéicas correspondentes. Uma árvore filogenética foi gerada para cada grupo de proteínas homólogas. Testes estatísticos determinaram qual entre os modelos de seleção neutra ou seleção positiva melhor explicou os dados existentes (alinhamentos de códons e árvores filogenéticas). Essas análises detectaram duzentas e cinquenta e quatro grupos de genes homólogos com evidência de seleção positiva. Para cada grupo foi realizado um teste de recombinação para verificar se o aumento na variação das sequencias não era devido à conversão gênica, resultando em cento e dezesseis grupos de genes homólogos sob seleção positiva. A proteína correspondente a um gene de cada grupo de genes homólogos foi identificada, por meio da ferramenta Blast. Diversos fatores de virulência, já conhecidos, e proteínas regulatórias puderem ser detectados. Os genes sob seleção positiva, também foram submetidos à anotação considerando o termo GO (Gene Ontology),apenas da categoria processo biológico. Dos cento e dezesseis genes apenas cinquenta e sete puderam ser identificados por meio dessa metodologia. O resultado da classificação dos genes dentro da classe GO, considerando o terceiro nível hierárquico,mostrou que a maioria dos genes anotados (31) tinha relação com o metabolismo primário.As proteínas cuja identificação, por meio do blast, não foi possível (proteínas hipotéticas)foram submetidas à análise de predição de localização subcelular e de peptídeo sinal. Essas análises revelaram que três proteínas desconhecidas (hypothetical proteinECIAI39_1028, hypothetical proteinZ0639e hypothetical proteinEC042_3791) são potenciais alvos para estudos que visam à busca de novos fatores de virulência de Escherichia coli patogênicas
Abstract: The bacterium Escherichia coli colonizesthe intestinal tract of birds and humans, in a commensal relationship without causing infection. However, some clones have acquired specific virulence factors allowing the development of various diseases such as urinary tract infection, diarrhea and meningitis in humans and colibacillosis in poultry. The strains that cause disease in birds are typically named APEC (Avian Pathogenic Escherichia coli). In this study we sequenced and annotated the genomes of four APECs strains (SCI-07, SEPT362, S17 and O8). These genomes and nine others avian pathogenic Escherichia coli and humans pathogenic strains genomes were used for studying genes under positive selection. The homologous genes were grouped and then subjected to codons and corresponding protein sequences alignment. A phylogenetic tree was generated for each group of homologous proteins. Statistical tests determined which among neutral or positive selection models best explains the existing data (codon alignments and phylogenetic trees). This analyzes detected two hundred fifty-four groups of homologous genes with positive selection evidence. For each group a recombination test was conducted to verify if the variation increase in the sequences was not due to gene conversion, resulting in one hundred and sixteen groups of homologous genes under positive selection. The protein corresponding to a gene of each group of homologous genes under positive selection was identified through Blast tool. Genes under positive selection were annotated considering the GO term (Gene Ontology), just for the biological process category. Only fifty-seven genes could be identified using this methodology. The gene classification within the GO classes, considering only the third hierarchical level showed that most of the annotated genes (31) were related with the primary metabolism. Proteins which blast identification was not possible (hypothetical proteins) were subjected to sub cellular localization and signal peptide prediction analyzes. These analyzes revealed that three unknown proteins (hypothetical protein ECIAI39_1028, hypothetical protein Z0639e hypothetical protein EC042_3791) are potential targets for studies, in order to search for new virulence factors of pathogenic Escherichia coli
Doutorado
Microbiologia
Doutora em Genética e Biologia Molecular
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Guilhabert, Magalie. "Development of molecular genetic systems for identifying pathogenicity genes in Xylella fastidiosa, the bacterial pathogen causing Pierce's disease of grapevines /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Main-Hester, Kara L. "Counter-silencing of laterally acquired genes, including Salmonella Pathogenicity Island 4, by three DNA binding proteins, HilA, HilD, and SlyA /." Thesis, Connect to this title online; UW restricted, 2008. http://hdl.handle.net/1773/11498.
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Funnell, Deanna Lillian. "The inheritance of pathogenicity genes in Nectria haematococca mating population VI and the association of virulence of pea with dispensable chromosomes." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/288699.
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Many plants produce toxic compounds, called phytoalexins, in response to infection by microorganisms. Some fungal pathogens of these plants can detoxify their host's phytoalexins and genetic studies of the ascomycete, Nectria haematococca Mating Population VI have established an association between detoxification of the pea phytoalexin, pisatin (Pda), and pathogenicity. Previous studies of one of the six genes (PDA) that confer this trait (PDA6-1) was on a dispensable chromosome. In the current study, a technique was developed that uses the pea plant to select for highly virulent recombinant progeny from crosses in which such progeny were relatively rare. It was demonstrated that when pea plants are inoculated with a mixture of ascospores that isolates recovered from pea lesions showed a strong bias for Pda and for being more virulent on pea, compared with ascospore progeny which did not undergo selection on plant. Additionally, all highly virulent isolates had PDA1-1, one of the three PDA genes present in the cross parents, showing that PDA1-1, or a linked gene, was necessary for virulence on pea. In the current study, highly virulent isolates were also identified by screening progeny from crosses that involved a highly virulent parent, 34-18. Analysis of 34-18 and its progeny showed that this isolate contains three PDA genes, PDA5 and PDA9, which were characterized in this study, and an allele of a previously characterized PDA gene. All three genes were associated with virulence on pea and could be lost during genetic crosses. Electrophoretic karyotype (CHEF) analysis showed that this was due to loss of a 1.5 Megabase chromosome carrying PDA1-2 and at least a portion of a 4.9 Mb chromosome carrying PDA5 and PDA9. CHEF analysis also showed that the other previously characterized PDA genes (PDA1-1, PDA2, PDA3, PDA4, PDA6-1 and PDA6-2) were on dispensable chromosomes. These dispensable chromosomes were not required for pathogenicity on carrot and ripe tomato. The results from this work provide evidence to support the hypothesis that the PDA chromosomes are dispensable, that some of them contain genes conferring virulence specifically on pea and genes for pathogenicity on other hosts were on non-PDA chromosomes.
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Barbosa, Fernanda de Oliveira [UNESP]. "Importância dos genes fliC e motB de Salmonella enterica subsp. enterica sorovar Enteritidis na colonização intestinal e invasão sistêmica em aves (Gallus gallus domesticus)." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/137909.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Salmonella Enteritidis (SE) causa o paratifo aviário em aves e frequentemente está relacionada aos surtos de infecção alimentar em seres humanos. A contribuição do flagelo versus motilidade na interação patógenohospedeiro requer estudos mais aprofundados. Para melhor entendimento da contribuição individual desses fatores de virulência em aves, pintinhos de um dia de vida foram desafiados oralmente com estirpe selvagem de SE, uma mutante não-móvel mas flagelada (SE ΔmotB) e outra mutante aflagelada (SE ΔfliC). Excreção fecal e colonização de fígado, baço e conteúdo cecal pelas estirpes de SE foram avaliadas. Além disso, também foi realizada a avaliação das alterações macroscópicas e microscópicas. Nos estágios iniciais da infecção, ambos mutantes mostraram menor capacidade de colonizar o ceco, além de menor recuperação no baço por SE ΔfliC comparando a estirpe selvagem SE. Após 7 dpi não havia diferenças na contagem das três estirpes em conteúdo cecal, fígado e baço. Análises histopatológicas demonstraram que estirpes flageladas (SE ΔmotB e SE) induziram reatividade linfóide em inglúvio, ceco, íleo e fígado. No entanto, nos estágios iniciais da infecção a estirpe SE ΔfliC não estimulou a reatividade linfóide em lâmina própria de ceco e íleo mas induziu discretos focos necróticos em fígado. Portanto, neste estudo a presença de estrutura flagelar e motilidade parece exercer um papel nos estágios iniciais da colonização intestinal e infecção sistêmica por SE nas aves.
Salmonella Enteritidis (SE) causes fowl paratyphoid in poultry often related to outbreaks of food-borne diseases in humans. The contribution of flagella and motility in host pathogen interaction require further investigation. To better understand the individual contribution of these virulence factors in poultry, one day old chickens were challenged orally with wildtype strain of SE, a nonmotile but fully flagellated (SE ΔmotB) and aflagellated mutant (SE ΔfliC). Faecal excretion and colonization of liver, spleen and cecal contents by the SE strains were assessed. Additionally, the assessment of gross and microscopic alterations was also performed. At the early stages of infection both mutants showed lower capacity to colonize the ceca, besides the lower recovering in spleen of SE ΔfliC comparing to the wild type of SE. After 7 dpi there were no differences among the counts of the three strains in ceca, liver and spleen. Histopathological analyses demonstrated that flagellated strains (wild type SE and SE ΔmotB) induced lymphoid reactivity in crop, ceca, ileum and liver. On the other hand, in the early stages of infection, SE ΔfliC strain did not stimulate lymphoid reactivity in lamina propria of ceca and ileum but induced discrete necrotic foci in liver. Thus in the present study the flagellar structure and motility seemed to play a role at the early stages of the intestinal colonization and systemic infection by SE in the chicken.
FAPESP: 2014/02014-1
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Pace, Fernanda de 1981. "Estudo de genes do Sistema de Secreção tipo VI em uma linhagem de Escherichia coli patogênica para aves (APEC)." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317391.
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Orientadores: Wanderley Dias da Silveira, Eliana Guedes StehlingTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Linhagens de Escherichia coli patogênica para aves (APEC) causam infecções extraintestinais e são responsáveis por significativas perdas econômicas na indústria avícola mundial. Recentemente, foram descritos isolados de APEC geneticamente relacionados a diversas outras E.coli extraintestinais (ExPEC) de origem humana, indicando a possibilidade das mesmas constituírem risco zoonótico para humanos. Alguns dos conhecidos fatores de virulência de APEC incluem adesinas, sistema de aquisição de ferro, citotoxinas, entre outros. Nesse trabalho, demonstramos que a linhagem de APEC SEPT 362, isolada do fígado de uma ave apresentando sinais clínicos de septicemia, expressa o Sistema de Secreção Tipo VI (SST6), causa rearranjo do citoesqueleto de células epiteliais cultivadas in vitro, é capaz de aderir e invadir células HeLa e é viável dentro de macrófagos. Para estudar o envolvimento do SST6 na patogênese da linhagem SEPT362, foram deletados três genes desse sistema: hcp, que codifica para uma proteína estrutural e secretada, clpV, que codifica para uma ATPase e icmF (intracellular multiplication factor), gerando três mutantes, respectivamente. Todos os mutantes demonstraram uma diminuição nos processos de adesão e invasão a células HeLa, formação de biofilme e virulência in vivo. Estudos de transcriptoma mostraram que a expressão da fímbria tipo 1 encontra-se diminuída nesses mutantes, o que poderia ser responsável pela diminuição do processo de adesão e invasão às células epiteliais. Nesse trabalho, demonstramos que o SST6 é importante para o processo de patogenicidade, visto que todos os mutantes tiveram sua virulência atenuada em experimentos realizados in vivo com uma significativa diminuição de características relacionadas à patogenicidade in vitro. Esses resultados demonstram que os genes estudados do SST6 influenciam a expressão da fímbria tipo 1 e contribuem para a patogênese desta linhagem APEC
Abstract: Avian pathogenic Escherichia coli (APEC) strains frequently cause extraintestinal infections and are responsible for significant economic losses in the poultry industry worldwide. APEC isolates are closely related to human extraintestinal pathogenic E. coli (ExPEC) strains and may also act as pathogens for humans. Known APEC virulence factors include adhesins such as type 1 fimbriae and curli, iron acquisition systems, and cytotoxins, among others. Here we demonstrated that APEC strain SEPT362, isolated from a septicemic hen, expresses a type VI secretion system (T6SS), causes cytoskeleton rearrangements, invades epithelial cells, replicates within macrophages, and causes lethal disease in chicks. To assess the contribution of the T6SS to SEPT362 pathogenesis, we generated three mutants, ?hcp (which encodes a protein suggessed to be both secreted and a structural component of the T6SS), ?clpV (encoding the T6SS ATPase) and ?icmF (intracellular multiplication factor). All mutants showed decreased adherence and invasion to HeLa cells and decrease in several other pathogenicity related characteristics. Transcriptome studies showed that the level of expression of type 1 fimbriae was decreased in these mutants, which may account for the diminished adhesion and invasion of epithelial cells. The T6SS seems to be important for the disease process, given that both mutants (?hcp and ?clpV) were attenuated in an infection model in chicks. These results suggest that the T6SS influences the expression of type 1 fimbriae and contributes to the pathogenesis of this APEC strain pathogenesis
Doutorado
Genetica de Microorganismos
Doutor em Genetica e Biologia Molecular
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Hoppenau, Clara Elisabeth [Verfasser], Gerhard [Akademischer Betreuer] Braus, and Ursula [Akademischer Betreuer] Kües. "Characterization of the pathogenicity relevant genes THI4 and PA14_2 in Verticillium dahliae / Clara Elisabeth Hoppenau. Gutachter: Gerhard Braus ; Ursula Kües. Betreuer: Gerhard Braus." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://d-nb.info/1047706857/34.
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Scarpari, Leandra Maria. "Modulação da expressão de genes de patogenicidade putativos em Xylella fastidiosa sob condições de baixa e alta densidade celular." Universidade de São Paulo, 2002. http://www.teses.usp.br/teses/disponiveis/11/11138/tde-18062002-093603/.
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Xylella fastidiosa (Xf) é o agente causal de doenças em várias culturas economicamente importantes. Recentemente foi identificada como sendo o agente causal da clorose variegada dos citros (CVC), doença que representa um grande problema para os citricultores paulistas, pois vem causando perdas econômicas significativas. Trata-se de uma bactéria gram-negativa, fastidiosa e restrita ao xilema das plantas hospedeiras. Um fato observado na interação Xf - citros, é que plantas infectadas por Xf podem demonstrar sintomas da doença um longo tempo após a infecção. Isto faz supor que a expressão de fatores de patogenicidade e/ou virulência ocorre somente após a população de Xf na planta atingir altas densidades celulares. Como fatores de patogenicidade/virulência de algumas bactérias são regulados por sensores de quorum, seria interessante determinar se esse mecanismo de regulação gênica ocorre em Xf, e quais genes bacterianos são regulados por densidade celular. O objetivo deste trabalho foi verificar se genes de patogenicidade putativos de Xf são modulados pela densidade celular em meio de cultura. Para tal, Xf foi cultivada em PW líquido, células no início da fase exponencial (baixa densidade celular) e na fase estacionária (alta densidade celular) foram coletadas, e RNA total foi extraído. Fragmentos de 20 genes de Xf relacionados à patogenicidade putativos foram transferidos em arranjos ordenados para membranas de náilon, e hibridizados, sob condições de alta estringência, com sondas complexas de primeiras fitas de cDNA marcadas com fosfatase alcalina. A detecção foi feita por quimioluminescência. Sob as condições experimentais utilizadas, os genes fur (XF-2344), gumC (XF-2369), protease-serina (XF-1851) e rsmA (XF-0125) tiveram sua expressão significativamente suprimida sob condições de alta densidade celular (p < 0,05). Já a expressão de rpfF (XF-1115) foi induzida significativamente (p < 0,06) sob condições de alta densidade celular. Os genes gumD (XF-2367), gumJ (XF-2362) e rpfA (XF-0290) tiveram a expressão detectada somente sob condições de alta densidade celular, enquanto a expressão de rpfB (XF-0287) foi detectada somente sob condições de baixa densidade celular. A expressão de celulase (XF0818), mdoH (XF-1623), pluxR (XF-0972), protease-RE (XF-1823), rpoN (XF-1408), xpsK (XF-1523) e xpsL (XF-1524) não foi afetada significativamente pela densidade populacional em meio PW, enquanto a expressão dos genes luxR/UHPA (XF-2608), poligalacturonase (XF-2466), rpfC (XF-1114) e rsmB (XF-0928) não foi detectada em ambas as condições. Usando RT-PCR, os transcritos de todos os genes, exceto gumC, foram detectados sob condições de baixa e alta densidade celular, indicando que a expressão de alguns genes relacionados à patogenicidade putativos em meio de cultura é muito baixa. Os resultados obtidos sugerem que os EPS são sintetizados por Xf predominantemente em condições de alta densidade celular em meio PW. Adicionalmente, os dados sugerem que Xf sintetiza uma molécula sinal similar à de Xcc em meio PW sob condições de alta densidade celular, e que a disponibilidade de ferro pode ser importante para a regulação gênica em condições de alta densidade celular. É possível que o padrão de expressão gênica observado possa ser alterado em função do meio de cultivo ou in planta.Xylella fastidiosa (Xf) is the causal agent of several economically important plant diseases. Recently, Xf has been identified as the causal agent of citrus variegated chlorosis (CVC), a disease that represents a major economic problem for citrus growers in the São Paulo State. Xf is a gram-negative, fastidious and xylem-limited bacterium. Based on the fact that plants may show disease symptoms a long time after infection in Xf-citrus interaction, we hypothesize that the expression of pathogenicity/virulence factors in Xf occurs after the bacterial population reach high cell densities. Since pathogenicity/virulence factors of some bacteria are quorum-sensing regulated, it would be interesting to determine whether this mechanism of genetic regulation occurs in Xf, and which genes are regulated by cell-density. In order to determine whether Xf putative pathogenesis-related genes are modulated by cell-density in culture media, Xf was grown in liquid PW and cells were sampled at early log (low cell density) and stationary phase (high cell density) and total RNA was extracted. Fragmentos of 20 putative pathogenicity-related genes from Xf were hybridized on ordered arrays nylon membranes to alkaline phosphatase-labeled first strand cDNA from low and high celldensity conditions as probes, at high stringency conditions. Detection was performed using chemiluminescence. Our results indicate that the following putative pathogenicity-related genes are significantly suppressed (p < 0.05) at high cell-density conditions: fur (XF-2344), gumC (XF-2369), serine-protease (XF-1851) and rsmA (XF-0125). The expression of rpfF (XF-1115) was significantly induced (p < 0.06) at high cell-density conditions. Expression of gumD (XF-2367), gumJ (XF-2362) and rpfA (XF-0290) was detected only at high cell-density conditions, whereas expression of rpfB (XF-0287) was detected only at low cell-density conditions. The expression of cellulase (XF0818), mdoH (XF-1623), pluxR (XF-0972), protease-RE (XF-1823), rpoN (XF-1408), xpsK (XF-1523) and xpsL (XF-1524) was not affected by the Xf population density in PW medium, whereas expression of luxR/UHPA (XF-2608), polygalacturonase (XF-2466), rpfC (XF-1114) and rsmB (XF-0928) was not detected under our experimental conditions. Using RT-PCR, transcripts for all genes, except gumC, were detected under low or high cell densities, indicating that the expression of some putative pathogenesis-related genes in culture medium is very low. Our results suggest that EPS may be synthesized by Xf mainly at high cell density conditions in PW medium. Additionally, our data suggest that Xf may synthesize a signal molecule similar to the Xcc in PW medium at high cell density conditions, and that iron availability may be important for gene regulation at high cell density conditions. It is possible that gene expression patterns observed under our experimental conditions may be altered with the culture medium used or when Xf grows in planta.
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Pope, David D. "A biometrical study of the effect of nonspecific pathogenicity genes on host and pathogen fitness related characters in the Ustilago hordei-Hordeum vulgare system." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/27187.
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Nine Ustilago hordei sporidia that produced 20 dikaryons were isolated at random from an F2 teliospore (18D1+ x 20C1-) descended from race 7 and race 11. The 20 dikaryons were homozygous for a dominant gene conferring virulence on the barley variety Trebi and were suspected of segregating for nonspecific pathogenicity genes on this variety. Varieties Odessa (the universal suscept, with no known specific resistance genes) and Trebi were inoculated with each dikaryon and 58 host and pathogen fitness related variables were measured.
Yield reduction occurred both in diseased and healthy plants as a result of the dikaryon treatments. A statistically significant negative correlation between host and pathogen reproductivity was found (r=-0.466, P=0.0481) on Trebi but not on Odessa.
Statistically significant differences among dikaryons were found for some fitness related variables. The segregation of nonspecific pathogenicity genes with pleiotropic effects was believed to cause these differences. One of the genes was found to be tightly linked to the mating locus, coupled with the "-" mating allele. Analysis of variance revealed significant dominance and/or epistatic interaction effects on fitness related variables.
The two varieties reacted differently to the dikaryons. Pathogen isolates exhibited specific adaptation to Trebi but not to Odessa. The presence of the nonspecific pathogenicity genes was readily measured statistically on Trebi, in the background of a matched specific resistance gene but not on Odessa.
The traditional method of measuring disease damage level (percent smutted plants) was determined to be a reliable estimator of pathogen fitness on Trebi (R²=0.84) and pathogen reproductivity on both varieties (r=0.902, P=0.0001 on Trebi and r=0.815, P=0.0001 on Odessa). Due to weak correlation, prediction of host fitness should not be attempted using values calculated with either of the two traditional methods of measuring disease damage level (percent smutted plants and percent smutted heads).
Stepwise regression of various combinations of variables indicated that Trebi, Odessa or smut dikaryon fitness can be accurately estimated with certain predictor variables.
Spearman rank correlation tests suggested that "constant (concordant) ranking" of dikaryons for percent smutted plants and for pathogen fitness was evident on Odessa and on Trebi (r=0.871, P=0.0001 and r=0.713, P=0.0004, respectively).Science, Faculty of
Botany, Department of
Graduate
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Lee, Nakhyung. "Characterization of an ATP-binding cassette (ABC) transport system involved in nucleoside uptake in Mycoplasma bovis strain M23, and discovery of its pathogenicity genes." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3373444.
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Rezende, Janayne Maria. "Diversidade filogenética e expressão de genes de virulência de Metarhizium com ênfase em isolados brasileiros associados a cultura da cana-de-açúcar." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11146/tde-04022015-151555/.
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O controle biológico de cigarrinha com Metarhizium (Hypocreales: Clavicipitaceae) na cana-de-açúcar é um exemplo de sucesso da aplicação do manejo sustentável de pragas no Brasil. No entanto, pouco se sabe sobre a riqueza, distribuição e ecologia das espécies de Metarhizium nos agroecossistemas e ambientes naturais no Brasil. Neste trabalho, avaliou-se a diversidade genotípica e realizou-se a identificação específica de 96 isolados depositados na Coleção de Entomopatógenos \"Prof. Sérgio Batista Alves\" da ESALQ-USP pelo sequenciamento da região 5\' do fator de alongamento da tradução 1 alfa (5\'-TEF) e das regiões espaçadoras intergênicas do DNA nuclear MzIGS3 e MzFG543igs. Observou-se a existência de 10, 11 e 17 haplótipos pelas sequências destes genes, respectivamente. Foram ainda obtidos 41 isolados de dois talhões de canavial em Araras-SP que consistiram em 9 haplótipos pela região MzIGS3. Foi observada a existência de cinco espécies de Metarhizium, duas atualmente reconhecidas, M. anisopliae s.l. e M. robertsii s.l., sendo estes os dois clados mais abundantes e três novas linhagens não caracterizadas taxonomicamente, referidas aqui como Metarhizium sp. indet. 1, Metarhizium sp. indet. 2 e Metarhizium sp. indet. 3. Com exceção de um único isolado todos os outros provenientes de insetos, incluindo os isolados de cigarrinha, pertencem a um único clado de M. anisopliae s.l. M. robertsii foi obtido exclusivamente a partir de amostras de solo ou rizosfera. Apesar de proporcionar um maior grau de resolução genética entre os isolados a região MzIGS3 se mostrou incapaz de reconstruir a filogenia consenso para o clado PARB, dificultando a sua utilização como sequência diagnóstica na identificação ou análise filogenética de espécies de Metarhizium. Além disso, foi desenvolvida uma técnica de bioensaio em laboratório para avaliação de patogenicidade de Metarhizium spp. sobre M. fimbriolata com mortalidade da testemunha inferior a 12%, após 28 dias de avaliação. A caracterização da expressão dos genes pr1A, mad1 e mpl relacionados à virulência de três isolados de M. anisopliae (ESALQ 1037, ESALQ 1641 e ESALQ 1204) cultivados em meio mínimo e meio mínimo com cutícula de M. fimbriolata, D. saccharalis e T. molitor não revelou uma associação entre a expressão relativa desses genes ea virulência dos fungos in vivo. As informações contidas neste trabalho poderão contribuir em estudos de identificação e caracterização de Metarhizium em habitats naturais e agrícolas de no Brasil e países vizinhos na América do Sul, assim como auxiliar no contínuo desenvolvimento e acompanhamento do programa de controle biológico de M. fimbriolata com Metarhizium na cultura da cana-de-açúcar.Biological control of spittlebug with Metarhizium (Hypocreales: Clavicipitaceae) in sugarcane is an example of the successful application of sustainable pest management in Brazil. However little is known about the richness, distribution and ecology of Metarhizium species in agroecosystems and natural environments of Brazil. In this study, the genotypic diversity was accessed and species designation was assigned for 96 Metarhizium strains deposited in the Collection of Entomopathogens \"Prof. Sérgio Batista Alves\" from ESALQ-USP using the sequence variation at 5\'-TEF and the nuclear intergenic loci MzFG543igs and MzIGS3. Sequence diversity at these loci included 10, 11 and 17 sequence haplotypes, according to these loci, respectively. 41 strains were recovered from two sugarcane fields and consisted of 9 haplotypes according to MzIGS3. Five species of Metarhizium were observed, being the two most abundant taxa, Metarhizium anisopliae, Metarhizium robertsii and an additional three taxonomically unassigned lineages are referred to here as Metarhizium sp. indet. 1, Metarhizium sp. indet. 2 and Metarhizium sp. indet. 3. With a single exception, all strains isolated from insects belong to single clade of M. anisopliae, including the isolates infecting spittlebugs in sugarcane agroecosystems. M. robertsii was only recovered from soil or rhizosphere samples. Despite providing a greater degree of genetic resolution among strains, MzIGS3 revealed the inability to recapitulate the consensus phylogeny for the PARB clade and complicates its use as a stand-alone tool for species identification or phylogenetic analysis of Metarhizium. In addition, a laboratory bioassay technique was developed for pathogenicity screening of Metarhizium spp. on M. fimbriolata with low mortality on control group (8-12%) after 28 days of evaluation. The expression of genes pr1A, Mad1 and mpl of three M. anisopliae strains (ESALQ 1037, ESALQ1204 and ESALQ 1641) grown in minimal medium and minimal medium with M. fimbriolata, D. saccharalis or T. molitor cuticle apparently was not related to virulence of the fungi in vivo. Together these data will serve as resources for identification, discovery and communicating about Metarhizium biodiversity for insect biological control applications in Brazil and adjacent countries in South America, as well as assist in the ongoing development and monitoring of the biological control program of M. fimbriolata with Metarhizium in sugarcane fields.
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Muñoz, Bodnar Alejandra. "Function of TALE1Xam in cassava bacterial blight : a transcriptomic approach." Thesis, Montpellier 2, 2013. http://www.theses.fr/2013MON20009.
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Xanthomonas axonopodis pv. manihotis (Xam) est une bactérie à gram négatif causant le Cassava Bacterial Blight (CBB) sur Manihot esculenta Crantz. Le manioc représente une des sources les plus importantes de carbohydrates pour près d'un milliard de personnes sur terre et une source importante d'énergie du fait de sa forte concentration en amidon. Le CBB constitue une limitation importante à la production massive de manioc et nos connaissances sur cette maladie sont encore insuffisantes. La pathogénie de nombreuses phytobactéries dépend de l'injection d'effecteurs de type III via un système de sécrétion de type III dans la cellule eucaryote hôte Parmi tous les effecteurs référencés aujourd'hui, les effecteurs de type TAL pour Transcription Activator-Like sont particulièrement intéressant. Une fois injectés dans la cellule végétale, les effecteurs TAL sont importés au noyau et y modulent l'expression de gènes cibles au bénéfice de la bactérie. Chez Xam, TALE1Xam est le seul gène de cette famille qui a été étudié au niveau fonctionnel. Cette étude a pour objectif majeur d'identifier les gènes de manioc dont l'expression est modifiée en présence de TALE1Xam. Le transcriptome de plantes de manioc inoculées avec XamΔTALE1Xam vs. XamΔTALE1Xam (TALE1Xam) a été analysé par RNAseq. Les données obtenues confrontées à la recherche bioinformatique de promoteurs de gènes potentiellement directement activés par TALE1Xam ont permis d'établir une liste de gènes ciblés par TALE1Xam candidats. Un candidat majeur ressort de cette analyse comme étant particulièrement intéressant, il s'agit d'un gène codant un facteur de transcription de type B3 régulant l'activité de protéines de type "Heat Shock". L'analyse fonctionnelle de ce candidat permettra de valider sa fonction en tant que gène de sensibilité du manioc à XamXanthomonas axonopodis pv. manihotis (Xam) is a gram negative bacteria causing the Cassava Bacterial Blight (CBB) in Manihot esculenta Crantz . Cassava represents one of the most important sources of carbohydrates for around one billion people around the world as well as a source of energy due to its high starch levels content. The CBB disease represents an important limitation for cassava massive production and little is known about this pathosystem. Bacterial pathogenicity often relies on the injection in eucaryotic host cells of effector proteins via a type III secretion system (TTSS). Between all the type III effectors described up to now, Transcription Activator-Like Type III effectors (TALE) appear as particularly interesting. Once injected into the plant cell, TAL effectors go into the nucleus cell and modulate the expression of target host genes to the benefit of the invading bacteria by interacting directly with plant DNA. In Xam, only one gene belonging to this family has been functionally studied so far. It consists on TALE1xam. This work aim to identify cassava genes whose expression will be modified upon the presence of TALE1xam. By means of cassava plants challenged with Xam Δ TALE1xam vs. Xam + TALE1xam together with the TAL effectors code, statistical analyses between RNAseq experiments and a microarray containing 5700 cassava genes, we seek out direct TALE1xam target genes. Hence, through transcriptomic, functional qRT validation and specific artificial TALEs design we proposed that TALE1xam is potentially interacting with a Heat Shock Transcription Factor B3. Moreover we argue that this gene is responsible of the susceptibility during Xam infection. Furthermore this work represents the first complete transcriptomic approach done in the cassava/Xam interaction and open enormous possibilities to understand and study CBB
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Beinhoff, Malte Verfasser], Petr [Akademischer Betreuer] Karlovsky, Andrea [Akademischer Betreuer] Polle, and Heiko [Akademischer Betreuer] [Becker. "Molecular and functional characterization of potential pathogenicity related genes from Verticillium longisporum / Malte Beinhoff. Gutachter: Petr Karlovsky ; Andrea Polle ; Heiko C. Becker. Betreuer: Petr Karlovsky." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2012. http://d-nb.info/1043765417/34.
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Padilla, Sirera Natàlia. "Novel approaches for in silico identification of pathogenic variants in BRCA1 and BRCA2 hereditary breast and ovarian cancer predisposition genes." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670705.
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Variants germinals a les proteïnes BRCA1 i BRCA2 poden alterar la funció protectora d’aquestes a l’ADN, incrementant el risc de desenvolupar càncer de mama i ovari hereditari (HBOC). Identificació d’aquells individus portadors de variants patogèniques permet canalitzar-los en programes específics de prevenció i vigilància, augmentant les seves taxes de supervivència. Per això, en primer lloc, cal identificar quines de les variants són patogèniques. Malauradament, no sempre hi ha prou informació per arribar a una conclusió. En aquesta situació, els predictors de patogenicitat dissenyats per estimar computacionalment el dany causat per les variants poden proporcionar una valuosa informació.
En aquest treball presentem una nova família de predictors de patogenicitat per BRCA1 i BRCA2. Aquests predictors difereixen en el seu objectiu: un està entrenat per estimar l’impacte molecular de les variants sobre la funció HDR de BRCA1 i BRCA2, i l’altre està entrenat per estimar la significació clínica d’una variant, és a dir, si la seva classificació és patogènica o neutra. Els seus rendiments han estat provats i són comparables als d’altres mètodes àmpliament utilitzats en el camp. Addicionalment, vam presentar els predictors al repte ENIGMA de la 5a Avaluació Crítica de la Interpretació del Genoma (CAGI), trobant que els nostres mètodes, especialment aquells que estimen l’impacte funcional de les variants, es classifiquen en les primeres posicions en comparació amb les altres eines.
Per tal de difondre aquesta família de predictors a la comunitat científica, hem construït el lloc web BRASS (https://www.biotoclin.org/BRASS), on els usuaris poden analitzar les seves variants de BRCA1 i BRCA2 amb canvi de sentit. Els usuaris més avançats també poden interpretar les prediccions mitjançant una mètrica de fiabilitat i diversos gràfics contextualitzant la seva puntuació amb la d’un conjunt de variants curades manualment.
Independentment, hem aplicat els nostres coneixements sobre predictors de patogenicitat en un gran projecte internacional per caracteritzar un nou trastorn neurològic pediàtric causat per variants patogèniques a la histona H3.3. Vam combinar l’ús de predictors de patogenicitat estàndard amb evidències d’anàlisis estructurals i càlculs biofísics per proporcionar una visió mecanicista de l’impacte de les variants causals.Variantes germinales en las proteínas BRCA1 y BRCA2 pueden alterar la función protectora de estas en el ADN, incrementando el riesgo de desarrollar cáncer de mama y ovario hereditario (HBOC). Identificación de aquellos individuos portadores de variantes patogénicas permite canalizarlos hacia programas específicos de prevención y vigilancia, aumentando sus tasas de supervivencia. Para ello, en primer lugar, es necesario identificar cuáles de las variantes son patogénicas. Desafortunadamente, no siempre hay suficiente información para llegar a una conclusión. En esta situación, los predictores de patogenicidad diseñados para estimar computacionalmente el daño causado por las variantes pueden proporcionar una valiosa información. En este trabajo presentamos una nueva familia de predictores de patogenicidad para BRCA1 y BRCA2. Estos predictores difieren en su objetivo: uno está entrenado para estimar el impacto molecular de las variantes en la función HDR de BRCA1 y BRCA2, y el otro está entrenado para estimar la significancia clínica de una variante, es decir, si su clasificación es patogénica o neutra. Sus rendimientos han sido probados y son comparables a los de los métodos ampliamente utilizados en el campo. Además, presentamos los predictores al desafío ENIGMA de la 5ª Evaluación Crítica de la Interpretación del Genoma (CAGI), encontrando que nuestros métodos, especialmente aquellos que estiman el impacto funcional de las variantes, se clasifican en las primeras posiciones en comparación con las otras herramientas. Para difundir esta familia de predictores a la comunidad científica, hemos construido el sitio web BRASS (https://www.biotoclin.org/BRASS), donde los usuarios pueden analizar sus variantes de BRCA1 y BRCA2 con cambio de sentido. Los usuarios más avanzados también pueden interpretar las predicciones utilizando una métrica de confiabilidad y varios gráficos que contextualizan su puntuación a la de un conjunto de variantes seleccionadas manualmente. De forma independiente, aplicamos nuestro conocimiento sobre los predictores de patogenicidad en un gran proyecto internacional para caracterizar un nuevo trastorno neurológico pediátrico causado por variantes patogénicas en la histona H3.3. Combinamos el uso de predictores patogénicos estándar con evidencia de análisis estructurales y cálculos biofísicos para proporcionar una visión mecanicista del impacto de las variantes causales.
Germline variants in BRCA1 and BRCA2 can disrupt the DNA protective role of these proteins resulting in an increased risk of developing hereditary breast and ovarian cancer (HBOC). Identification of those individuals carrying pathogenic variants will allow channeling them into specific programs of prevention and surveillance, incrementing their survival rates. For this purpose, first, it is necessary to identify which of the variants are pathogenic. Unfortunately, there is not always enough information to reach a conclusion. In this situation, pathogenicity predictors designed to computationally estimate the damage caused by variants, can provide valuable information. Here, we present a novel family of pathogenicity predictors for BRCA1 and BRCA2. These predictors differ in their objective: one is trained to estimate the molecular impact of variants on the HDR function of BRCA1 and BRCA2, and the other is trained to estimate the clinical significance of a variant, that is, whether it should be classified as pathogenic or neutral. Their performances have been tested and are comparable to those of widely used predictors in the field. Additionally, we presented them to the ENIGMA challenge from the 5th Critical Assessment of Genome Interpretation (CAGI), finding that our predictors, especially those estimating the functional impact of variants, ranked in the top positions compared to other tools. In order to disseminate this family of predictors to the scientific community, we have built the BRASS website (https://www.biotoclin.org/BRASS), where users can analyze their missense BRCA1 and BRCA2 variants. More advanced users can also interpret the predictions using a reliability metric and several plots contextualizing the score to that of a set of manually curated variants. Independently, we applied our knowledge about pathogenicity predictors in a large international effort to characterize a novel pediatric neurologic disorder caused by pathogenic variants in histone H3.3. We combined the use of standard pathogenic predictors with evidence from structural analyses and biophysical computations to provide a mechanistic view of the impact of the causative variants.
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Cabral, Ana Cristina Garcia Pereira. "New insights in Ilyonectria black foot disease of grapevine." Doctoral thesis, ISA/UTL, 2012. http://hdl.handle.net/10400.5/5192.
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Doutoramento em Engenharia Agronómica - Instituto Superior de AgronomiaConsidering the growing importance of black foot disease of grapevine, this study was aimed to deeply understand details on taxonomy, genetics, biology and pathological behaviour of its main causal agents, previously attributed mostly to Ilyonectria liriodendri and I. macrodidyma. A multi-gene analysis of a collection of Ilyonectria isolates, along with morphological characterisation, enabled the description of 12 species from I. radicicola and four from I. macrodidyma complexes. Among these, pathogenicity experiments revealed I. lusitanica, I. estremocensis and I. europaea as more virulent to grapevine than I. liriodendri and I. macrodidyma. The entire mating-type loci of I. liriodendri and of species from the I. macrodidyma complex were obtained. While the idiomorph structure of species from the latter matches that of other heterothallic Hypocreales, the organization of the mating-type loci in I. liriodendri seems unique, suggesting a potential pseudo-heterothallism. Soilborne inoculum is accepted to contribute significantly to initiate black foot disease in grapevine plants. qPCR amplification from DNA soil samples demonstrate that rotation can reduce the levels of Ilyonectria in nurseries, and that levels of infestation in vineyard soils are lower than in nursery or mother-plant soils. Additionally, a protoplast transformation protocol is presented for the stable integration of the GFP gene in the genome of I. liriondendri, enabling future downstream functional genetic studies.
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Xu, Hai Quan [Verfasser], Petr [Akademischer Betreuer] Karlovsky, and Andreas von [Akademischer Betreuer] Tiedemann. "Determination of fungal gene expression in planta by qRT-PCR and characterization of putative pathogenicity related genes of Verticillium longisporum / Hai Quan Xu. Gutachter: Andreas von Tiedemann ; Petr Karlovsky. Betreuer: Petr Karlovsky." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044249463/34.
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Merighi, Massimo. "Molecular biology and biochemistry of regulation of Hrp/type III secretion genes in the corn pathogen Pantoea stewartii pv. stewartii." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1069854564.
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Thesis (Ph. D.)--Ohio State University, 2004.Document formatted into pages; contains xxxiii, 421 p. Includes bibliographical references. Abstract available online via OhioLINK's ETD Center; full text release delayed at author's request until 2005 Dec. 2.
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Lucas, Darren Edward. "Coordinated Regulation of Salmonella Virulence Genes by the BarA/SirA Two-Component System and the Csr Global Regulatory System." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1374087620.
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Paiva, Jacqueline Boldrin de 1984. "Mutagênese sítio-dirigida em uma linhagem de Escherichia coli (APEC) causadora de síndrome da cabeça inchada em aves = análises in vitro e in vivo." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/317392.
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Orientadores: Wanderley Dias da Silveira, Marcelo BrocchiTese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Escherichia coli patogênica para aves (APEC) é responsável por inúmeras perdas no setor avícola mundial, por causar uma série de doenças nas aves que se apresentam de forma sistêmica ou localizada as quais são, coletivamente, denominadas colibacilose. Os mecanismos de virulência destas linhagens patogênicas para aves e, possivelmente, patogênicas para seres humanos ainda não foram totalmente elucidados. Este trabalho foi desenvolvido com o intuito de estudar genes possivelmente envolvidos com a patogenicidade de uma linhagem APEC causadora de Síndrome da Cabeça Inchada (SCI-07) ONT:H31, a partir de resultados obtidos em um microarranjo realizado in vitro, o qual comparou a linhagem em estudo à linhagem padrão E. coli EHEC 8624 (linhagem enterohemorrágica). Nove genes, detectados como sendo super-expressos no microarranjo, nas condições estudadas, foram selecionados para construção de mutantes nulos e de seus complementos [feoA (transporte de ferro), nirC (transportador de nitrito), flgE ( gancho flagelar), tyrR (regulador de transcrição da síntese de aminoácidos aromáticos), potF (subunidade periplasmática do transportador putrescina), yehD (possível fimbria), bfr (bacterioferrina), csgA ( subunidade principal da curlina) e entD (enteroquelina)]. Os mutantes construídos foram avaliados quanto as suas capacidades de adesão e invasão em cultivos celulares, e quanto ao seu potencial patogênico em aves de um dia de idade em comparação à cepa selvagem. As linhagens ?bfr, ?csgA e ?nirC apresentaram diminuição da capacidade de adesão em fibroblastos de aves (linhagem FEG) em comparação à linhagem selvagem em ambos os modelos adotados: na presença e ausência de alpha-D-mannopyranoside; a linhagem ?potF apresentou diminuição da adesão apenas na ausência de alpha-D-mannopyranoside. Os mutantes ?csgA e ?tyrR apresentaram redução na capacidade de invadir linhagem de células de trato respiratório humano (linhagem Hep-2). Nenhum mutante avaliado mostrou alteração na capacidade de invadir fibroblastos de aves (linhagem CEC-32). Os mutantes ?flgE e ?tyrR mostraram diminuição na capacidade de invadir e sobreviver em macrófagos de aves (linhagem HD11). A motilidade das linhagens mutantes ?csgA, ?bfr, ?yehD, ?potF, ?entD, ?nirC e ?feoA foi aumentada enquanto o mutante ?tyrR mostrou redução de motilidade e o mutante ?flgE tornou-se imóvel. Nenhuma linhagem mutante obtida mostrou a mesma capacidade da linhagem selvagem em causar mortalidade em aves de um dia; ?feoA tornou-se hipervirulenta e todos os demais mutantes apresentaram atenuação em diferentes graus, sendo a linhagem ?entD totalmente atenuada e, portanto, promissora quanto ao seu uso como linhagem vacinal.para o combate à colibacilose em aves, ou como linhagem carreadoras de epítopos presentes em outras linhagens APEC
Abstract: Avian Pathogenic Escherichia coli (APEC) is responsible for significant economic loses in the poultry industry worldwide, by cause a range of systemic or localized diseases in poultry collectively termed colibacillosis. The virulence mechanisms of these pathogenic strains for poultry and possibly pathogenic for humans have not been fully elucidated. This work was developed in order to study genes potentially involved in the pathogenicity of an APEC strain isolated from a Swollen Head Syndrome case (SCI- 07) ONT:H31; since the results obtained in a microarray performed in vitro, which compared the SCI-07 strain to the standard strain E. coli 8624 EHEC (enterohemorrhagic strain). Nine overexpressed genes in microarray under the conditions studied were selected for construction of null mutants and their complements [feoA (iron transport), nirC (nitrite transporter), flgE (flagellar hook), tyrR (transcriptional regulator of the aromatic amino acids biosynthesis), potF (periplasmic putrescine transporter subunit), yehD (putative adhesin), bfr (bacterioferritin), csgA (major curling subunit) and entD (enterochelin)]. The mutants constructed were evaluated for their capacity for adhesion and invasion in cell cultures, and for its pathogenic potential in one-day-old chickens in comparison to the wild type strain (WT). The ?bfr, ?csgA and ?nirC strains showed decreased adhesion capacity on avian fibroblasts (CEF cells) compared to the WT in both models adopted: in the presence and absence of alpha-D-mannopyranoside, the ?potF strain showed decrease on adhesion only in the absence of alpha-D-mannopyranoside. The ?csgA and ?tyrR mutants had reduced ability to invade human larynx cell line (Hep-2 cells). No mutant showed changes in the capacity of invade avian fibroblasts birds (CEC-32cells). The ?flgE and ?tyrR mutants showed decreased ability to invade and survive into avian macrophages (HD11 cells). The motility of mutant strains ?csgA, ?bfr, ?yehD, ?potF, ?entD, ?nirC and ?feoA was increased while the ?tyrR mutant showed reduced motility and the mutant ?flgE became nonmotile. No mutant strain showed the same capacity of the WT in cause mortality in one-day-old chickes; ?feoA became hipervirulenta and all other mutants showed attenuation in different degrees, including the ?entD that was completely attenuated and a promising vaccine candidate strain to combat colibacillosis in poultry, or as a carrier strain of epitopes present in other APEC strains
Doutorado
Genetica de Microorganismos
Doutora em Genética e Biologia Molecular
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Ferreira, Gerson Moura. "Regulação da adesão de Escherichia coli enteropatogênica (EPEC) por genes de resposta à limitação nutricional e estresse." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/42/42132/tde-02122009-125957/.
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Escherichia coli enteropatogênica (EPEC) é uma das principais causas de diarreia em crianças. Na carência de fosfato (Pi), um conjunto de genes conhecido como regulon PHO é induzido. Esse regulon é controlado pelo sistema Pst, que além de ser um transportador de Pi, reprime a expressão de PHO quando Pi é abundante, e pelo sistema de dois componentes PhoB/PhoR. A deleção de pst reduziu a adesão de EPEC à células epiteliais in vitro, pois diminuiu da expressão dos reguladores PerA/PerC, que por sua vez controlam a expressão de genes envolvidos na adesão. Este efeito foi exclusivo de pst e não devido a expressão constitutiva dos genes de PHO causada pela deleção de pst. A expressão da fímbria BFP, PerA e PerC também dependem da síntese de ppGpp, uma molécula de alarme envolvida na regulação de genes relacionados à carência nutricional. ppGpp regula positivamente a expressão de PerA e PerC. Entretanto, RpoS, o fator relacionado à resposta ao estresse, afetou negativamente o nível de adesão de EPEC e a expressão de BFP.Enteropathogenic E. coli (EPEC) is one of the causes of diarrhea in children. Phosphate (Pi) shortage induces transcription of the genes known as the PHO regulon. These genes are controlled by the Pst system, that is also a high-affinity Pi transporter, and represses PHO expression under Pi-replete conditions. PHO is also controlled by the two-component system PhoB/PhoR. Deletion of the pst operon reduced the adhesion of EPEC to epithelial cells in vitro due to a decrease in the expression of the regulators PerA and PerC that in turn control the expression of genes related to adhesion. The constitutive expression of the PHO genes in the pst mutant was not the cause of adhesion inhibition. Expression of bfp and the regulators PerA and PerC was also dependent on ppGpp, an alarmone involved in the regulation of genes related to nutrient limitation. On the other hand, RpoS, the factor that controls the general stress response, negatively affected EPEC adhesion and bfpA expression.
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Jansson, Désirée S. "Genus Brachyspira in birds : phenotypes, phylogeny and pathogenicity /." Uppsala : Dept. of Clinical Sciences, Swedish University of Agricultural Sciences, 2009. http://epsilon.slu.se/200914.pdf.
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Garosi, Paola. "A study of gene expression in the take-all fungus Gaeumannomyces graminis." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267543.
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Heckel, Thierry. "Pathogenicity determinants and gene expression of maize streak virus." Thesis, University of East Anglia, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338099.
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Allen, Caitilyn. "Evolution of a gene for pathogenicity: endo-pectate lyase." Diss., Virginia Polytechnic Institute and State University, 1987. http://hdl.handle.net/10919/82610.
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Erwinia carotovora subsp. Carotovora (Ecc) and Erwinia carotovora subsp. Atroseptica (Eca) are plant pathogenic bacteria that cause soft rot disease of many plant species and blackleg disease of potatoes, respectively. Ecc and Eca attack plants by means of a group of extracellular plant tissue-degrading enzymes. which rapidly breaks down the pectic polymers that form a structurally important part of the plant cell wall, is considered central to soft rot pathogenesis. In this work, I isolated and studied the genes encoding this enzyme from Ecc and Eca. A clone library of Ecc strain EC14 was constructed using cosmid PLAFR3. This library contains 2,200 clones with an average insert size of 27 kilobases of DNA and included a proteolytic clone, five cellulolytic clones, and ten pectolytic clones. The proteolytic clone was used to complement a Tn5-induced protease mutant of Ecc; the complemented mutant was restored to near-wild type phenotype. Six of the pectolytic clones hybridized to a probe from a. previously isolated extracellular endo-pectate-pectate lyase gene from Ecc; one pectolytic clone had homology to a previously isolated clone encoding endo-polygalacturonase: three clones showed no
relationship to either of the previously characterized Ecc pectolytic enzyme genes. A clone encoding the major endo-pectate lyase gene from Ecc was chosen for subcloning and further study. I used the plasmid vector pBR322 to construct a clone bank of Eca strain SRB; of the 1700 clones screened, five were pectolytic. Two of the Eca pectolytic. clones had homology to the Ecc endo-pectate lyase gene; upon examination, they proved to contain the same insert in opposite orientations. The Ecc endo-pectate lyase had a pI of 9. 5 and a molecular weight of 33,000; the analogous Eca endo-pectate lyase had a pI of 9.2 and a molecular weight of 31,000. Both enzymes required a divalent cation for activity (preferring Ca2+ over Mg2+ over Mn2+. The restriction endonuclease maps of the two clones did not have any tested sites in common. These differences suggest that although these two genes may have originated from a common ancestral gene, considerable divergence has taken place. I analyzed the fine structure of the Ecc endo-pectate lyase gene by DNA sequencing. The coding region of the gene is preceded by E. coli-type -10 and -35 sequences and encodes an unmodified protein of 281 amine acids. A typical secretion signal peptide is not present.Ph. D.
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Slater, Holly. "The regulation of pathogenicity gene expression in Xanthomonas campestris mediated by a small diffusible molecule." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301935.
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Kim, Vic Narry. "Analysis of components of HIV in the development of new gene transfer systems." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389043.
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Beacham, Andrew Mark. "Pathogenicity determinants of Fusarium graminearum on wheat ears." Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3035.
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Some specialist microbes can deploy a range of mechanisms to cause disease on one or more host plant species. To identify entirely new classes of pathogenicity and virulence factors, a bioinformatics-reverse genetics approach has been applied to a plant pathogen where near complete genomic sequence information was available. A genomic region was identified on chromosome 1 of the important cereal pathogen Fusarium graminearum that contains a significant grouping of homologues of known virulence genes. Targeted deletion of these genes revealed a role for the neutral trehalase (NTH1) and protein kinase A regulatory subunit (PKAR) genes in the rate of disease symptom spread by F. graminearum, in addition to the previously reported SNF1 Ser/Thr protein kinase and STE7 MAP kinase kinase genes. Subsequent investigation of further genes at this locality revealed the presence of a gene, here named Fusarium graminearum Contributor to Virulence 1 (FCV1), which represent a novel class of gene required for a full rate of symptom spread. Targeted deletion of FCV1 led to a reduced rate of disease development by F. graminearum on wheat ears and Arabidopsis floral tissue, but did not affect trichothecene mycotoxin production. The fcv1 deletion mutant also exhibits altered hyphal growth, reduced asexual sporulation and altered sensitivity to oxidative and osmotic stress. In the complemented strain, wild-type traits were completely or partially restored. This micro-region of < 40 kb containing these five important genes represents a novel type of gene cluster containing genes required for a full rate of disease development. This micro-region is located in a genomic region of low recombination, is highly conserved in three other Fusarium species, but is less conserved in other plant pathogenic species. The micro-region is not defined by a distinct GC content or coordinated gene expression patterns, nor is it flanked by highly repetitive sequences. This micro-region is distinct from the previously identified fungal and bacterial virulence gene clusters and the clustered biosynthesis-associated genes required to synthesis metabolites which contribute to pathogenicity. This method for novel disease development-contributing gene identification is applicable to any sequenced pathogen species.
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Sheikh, Md Arif. "Structural biology of Vibrio cholerae pathogenicity factors." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/696.
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Soanes, Darren Mark. "Regulation of the pathogenicity gene MPG1 in the rice blast fungus Magnaporthe grisea." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368367.
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Mohmad, Mahyudin Murnita Binti. "Agrobacterium-mediated transformation of Corynespora cassiicola as a tool for pathogenicity gene discovery." Thesis, University of Bristol, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707740.
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Cunnac, Sébastien. "Identification à l'échelle génomique des effecteurs dépendant du système de sécrétion de type III de la bactérie phytopathogène Ralstonia solanacearum." Toulouse 3, 2004. http://www.theses.fr/2004TOU30197.
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La bactérie phytopathogène Ralstonia solanacearum est l'agent causal du flétrissement bactérien des solanées. Les gènes hrp codent pour un appareil de sécrétion de protéines, dit de type III, qui permet l'injection d'effecteurs du pouvoir pathogène à l'intérieur des cellules végétales hôtes. Le gène régulateur hrpB contrôle l'expression des composants de la machinerie Hrp et des substrats qui l'empruntent. La caractérisation du mécanisme d'action de HrpB a permis de définir un motif cis-opérateur conservé, la boite hrpII, indispensable à l'activité des promoteurs du régulon. Une liste de 114 gènes candidats a été constituée suite à la recherche de ce motif sur la séquence du génome de R. Solanacearum GMI1000. Dans un deuxième temps, l'analyse fonctionnelle des candidats identifiés par les approches in silico a été entreprise : 48 de ces gènes font partie du régulon hrpB. Neuf brg (gènes hrpB-régulés) sont homologues à des effecteurs de type III précédemment décrits chez d'autres bactéries phytopathogènes. Les 31 brg restants codent pour des protéines originales qui arborent un signal d'injection potentiel. La translocation hrp-dépendante de cinq protéines candidates dans des cellules végétales a été confirmée. L'étude du pouvoir pathogène des mutants d'insertion générés vis-à-vis de deux espèces hôtes indique que l'interaction n'est modifiée que pour un petit nombre d'entre eux. Finalement, nous avons caractérisé le gène avrA, qui conditionne l'aptitude de la bactérie à déclencher une réponse hypersensible sur différentes espèces de Nicotiana. L'ensemble de ces travaux suggère que le génome de R. Solanacearum héberge un répertoire d'effecteurs de type III considérable (50 à 70). La compréhension de leur contribution respective au pouvoir pathogène de R. Solanaceraum nécessitera l'élucidation de leur activité moléculaire sur le métabolisme de la cellule végétaleRalstonia solanacearum is the causal agent of bacterial wilt disease. Hrp genes encode a type III protein secretion apparatus that allows virulence effectors injection into the host plant cell. The regulatory gene hrpB controls expression of the structural components of the secretion machinery as well as its substrates. Characterization of the mode of action of HrpB allowed the definition of the hrpII box, a conserved cis-operator motif required for activity of the promoters belonging to this regulon. A search for this motif on R. Solanacearum GMI1000 genome sequence produced a list of 114 candidate genes. The next step involved the functional analysis of a group of these candidate genes : 48 of them were shown to belong to the hrpB regulon. Nine brg (hrpB-regulated genes) are homologous to known type III effectors from other plant pathogenic bacteria. The remaining 31 brg encode unknown or hypothetical proteins harbouring a putative type III-translocation signal. Hrp-dependent translocation into plant cells was confirmed for five candidate proteins. Only a few of the insertion mutants generated displayed an altered virulence when tested onto two host species. Finally, we identified and characterized the avrA gene which is necessary for elicitation of the hypersensitive response on some Nicotiana species. Altogether, these data suggest that R. Solanacearum genome contains a large type III effector repertory (50 to 70). Understanding their relative contribution to R. Solanacearum pathogenicity will await future elucidation of their molecular activity on the plant cell metabolism
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Meyer, Tanja. "Agrobacterium tumefaciens-mediated transformation of Fusarium oxysporum f. sp. cubense for pathogenicity gene analysis." Diss., University of Pretoria, 2008. http://hdl.handle.net/2263/25473.
Full textAbstract:
Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive plant diseases in recorded history. The disease was first discovered in Australia in 1874 but became renowned for the severe losses it caused to export banana plantations during the 1960s in Central America. The banana export industry was saved only by replacing Gros Michel bananas, the dessert banana grown for the export market, with highly resistant Cavendish banana cultivars. Despite this apparent solution, the fungus was found to attack Cavendish bananas in the sub-tropics, where plants were believed to be predisposed to the disease by the cool winter climate. Good management practices and conventional disease management strategies have not been sufficient to reduce losses and stop the disease from spreading, and today Fusarium wilt can be found in almost all banana-producing countries of the world. Since 1988, Foc has been responsible for significant losses of Cavendish bananas in tropical Asia. The only sustainable control measure, the use of resistant varieties, is not always popular as people prefer to eat locally adopted varieties that, unfortunately, are susceptible to Foc. Sustainable Fusarium wilt management in banana depends on the improvement of existing banana cultivars or the development of novel disease management strategies. Molecular biology and biotechnology provide opportunities to introduce foreign resistance genes into existing cultivars and to develop new, environmentally friendly products that can protect susceptible bananas from Foc. Better knowledge of the Fusarium wilt pathogen, its diversity, and its mechanisms of pathogenesis will contribute significantly to developing these novel approaches for control of the disease. Molecular information on the pathogenicity of Foc, however, is limited, whereas other formae speciales of F. oxysporum have been better studied. In this thesis, Agrobacterium tumefaciens-mediated transformation of (ATMT) was employed to investigate genes responsible for pathogenicity of Foc to banana. Chapter 1 provides an overview of pathogenicity in F. oxysporum. Pathogenic and non-pathogenic forms of the fungus are first introduced to the reader, and then the biology, epidemiology and etiology of pathogenic forms of F. oxysporum are discussed. The genetic make-up and ability of the Fusarium wilt fungus to cause disease in plants concludes the first part of the review. In recent years, there has been a noted increase in the number of techniques available to study hostpathogen interactions. The second part of the review concentrates on these techniques and their applications in studying pathogenicity of the Fusarium wilt pathogen. In Chapter 2, an ATMT and screening system for Foc was developed. Five A. tumefaciens strains were evaluated for their efficiency to transform Foc with a randomly integrating vector that confers hygromycin B resistance and expression of green fluorescent protein (GFP). A small insertion mutant library of Foc was created, and a subset of transformants was characterized by determining the number of T-DNA inserts present, the location and identity of predicted genes disrupted by T-DNA insertion, and whether transformants of Foc were altered in their virulence against susceptible banana plants. In Chapter 3, the role of a known pathogenicity gene, Frp1, of the tomato pathogen F. oxysporum f. sp. lycopersici (Fol) was investigated in Foc. The first objective was to isolate and characterize the Frp1 gene in Foc, and to compare it to the homologous gene in Fol. A vector containing a modified Fol Frp1 gene was then obtained and used for targeted disruption of the gene in Foc via ATMT. Mutants in which the Frp1 gene was disrupted were then analyzed for GFP expression, culture morphology, and alterations in pathogenicity to banana.Dissertation (MSc)--University of Pretoria, 2008.
Microbiology and Plant Pathology
unrestricted
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Meyer, Tania. "Agrobacterium tumefaciens-mediated transformation of Fusarium oxysporum f. sp. cubense for pathogenicity gene analysis." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-06122009-132700/.
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