Academic literature on the topic 'Virulence Operon'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Virulence Operon.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Virulence Operon"
1
Kitten, Todd, Cindy L. Munro, Suzanne M. Michalek, and Francis L. Macrina. "Genetic Characterization of a Streptococcus mutans LraI Family Operon and Role in Virulence." Infection and Immunity 68, no. 8 (August 1, 2000): 4441–51. http://dx.doi.org/10.1128/iai.68.8.4441-4451.2000.
Full textAbstract:
ABSTRACT Proteins belonging to the LraI (for “lipoprotein receptor antigen”) family function as adhesins in several streptococci, as a virulence factor for endocarditis in at least one of these species, and potentially as metal transporters in many bacteria. We have identified and characterized the chromosomal locus containing the LraI family gene (designated sloC) from Streptococcus mutans, an agent of dental caries and endocarditis in humans. Northern blot analysis indicated that sloC is cotranscribed with three other genes. As with other LraI operons, the sloA andsloB genes apparently encode components of an ATP-binding cassette transport system. The product of the fourth gene,sloR, has homology to the metal-dependent regulator fromCorynebacterium diphtheriae, DtxR. A potential binding site for SloR was identified upstream from the sloABCR operon and was conserved upstream from LraI operons in several other streptococci. Potential SloR homologs were identified in the unfinished genomic sequences from two of these, S. pneumoniae andS. pyogenes. Mutagenesis of sloC in S. mutans resulted in apparent loss of expression of the entire operon as assessed by Northern blot analysis. The sloCmutant was indistinguishable from its wild-type parent in a gnotobiotic rat model of caries but was significantly less virulent in a rat model of endocarditis. Virulence for endocarditis was restored by correction of the sloC mutation but not by provision of thesloC gene in trans, suggesting that virulence requires the expression of other genes in the sloC operon.
2
Salvail, Hubert, Jeongjoon Choi, and Eduardo A. Groisman. "Differential synthesis of novel small protein times Salmonella virulence program." PLOS Genetics 18, no. 3 (March 4, 2022): e1010074. http://dx.doi.org/10.1371/journal.pgen.1010074.
Full textAbstract:
Gene organization in operons enables concerted transcription of functionally related genes and efficient control of cellular processes. Typically, an operon is transcribed as a polycistronic mRNA that is translated into corresponding proteins. Here, we identify a bicistronic operon transcribed as two mRNAs, yet only one allows translation of both genes. We establish that the novel gene ugtS forms an operon with virulence gene ugtL, an activator of the master virulence regulatory system PhoP/PhoQ in Salmonella enterica serovar Typhimurium. Only the longer ugtSugtL mRNA carries the ugtS ribosome binding site and therefore allows ugtS translation. Inside macrophages, the ugtSugtL mRNA species allowing translation of both genes is produced hours before that allowing translation solely of ugtL. The small protein UgtS controls the kinetics of PhoP phosphorylation by antagonizing UgtL activity, preventing premature activation of a critical virulence program. Moreover, S. enterica serovars that infect cold-blooded animals lack ugtS. Our results establish how foreign gene control of ancestral regulators enables pathogens to time their virulence programs.
3
Day, William A., and Anthony T. Maurelli. "Shigella flexneri LuxS Quorum-Sensing System Modulates virB Expression but Is Not Essential for Virulence." Infection and Immunity 69, no. 1 (January 1, 2001): 15–23. http://dx.doi.org/10.1128/iai.69.1.15-23.2001.
Full textAbstract:
ABSTRACT Quorum-sensing systems regulate the expression of virulence factors in a wide variety of plant and animal pathogens, including members of the Enterobacteriaceae. Studies of Shigellavirulence gene expression have demonstrated that maximal expression of genes encoding the type III secretion system and its substrates and maximal activity of this virulence organelle occur at high cell density. In these studies, we demonstrate that the expression ofipa, mxi, and spa invasion operons is maximal in stationary-phase bacteria and that conditioned media derived from stationary-phase cultures enhance the expression of these loci. In contrast, expression of virB, a transcription factor essential for the expression of invasion loci, peaks in late log phase; accordingly, virB expression is enhanced by a signal(s) present in conditioned media derived from late-log-phase cultures. Autoinducer 2 (AI-2), a quorum signaling molecule active in late log phase, was synthesized by Shigella species and enteroinvasive Escherichia coli and shown to be responsible for the observed peak of virB expression. However, AI-2 does not influence invasion operon expression and is not required forShigella virulence, as mutants deficient in AI-2 synthesis are fully virulent. The implications of these findings with regard to both virB and invasion operon expression and the evolution of circuitries governing virulence gene expression are discussed.
4
Miranda-CasoLuengo, Raúl, Aleksandra A. Miranda-CasoLuengo, Enda P. O’Connell, Ruth J. Fahey, Clara A. Boland, Jose A. Vázquez-Boland, and Wim G. Meijer. "The vapA co-expressed virulence plasmid gene vcgB (orf10) of the intracellular actinomycete Rhodococcus equi." Microbiology 157, no. 8 (August 1, 2011): 2357–68. http://dx.doi.org/10.1099/mic.0.049759-0.
Full textAbstract:
The virulence plasmid of the pathogenic actinomycete Rhodococcus equi is essential for proliferation of this pathogen in macrophages and the development of disease. The pathogenicity island of this plasmid encodes a family of virulence-associated proteins (Vap), one of which (VapA) is a virulence factor. This paper describes the vcgAB operon ( vapA co-expressed gene), located upstream of the vapA operon. Transcription of the vcgAB operon gave rise to transcripts with a half-life similar to those determined for other virulence plasmid genes (1.8 min). Transcription started at a promoter similar to the vapA promoter, and proceeded through an inefficient terminator into the downstream vcgC gene. In addition, vcgC is also transcribed from a promoter downstream of vcgB. The vcgAB and vapA operons were coordinately regulated by temperature and pH in a synergistic manner. The latter parameter only affected transcription at higher growth temperatures, indicating that temperature is the dominant regulatory signal. Transcription of the vcgAB operon increased 10-fold during the late exponential and stationary growth phases. Transcription was also upregulated during the initial hours following phagocytosis by phagocytic cells. In contrast to vcgA and vcgC, the vcgB gene is conserved in the porcine VapB-encoding plasmid, as well as in pathogenic mycobacteria. The coordinated regulation of vcgB and vapA, transcription of vcgB following phagocytosis and conservation of vcgB in pathogenic mycobacteria indicate a role for vcgB and the vcg genes in the virulence of R. equi.
5
Tobe, Toru, Tetsuya Hayashi, Chang-Gyun Han, Gary K. Schoolnik, Eiichi Ohtsubo, and Chihiro Sasakawa. "Complete DNA Sequence and Structural Analysis of the Enteropathogenic Escherichia coli Adherence Factor Plasmid." Infection and Immunity 67, no. 10 (October 1, 1999): 5455–62. http://dx.doi.org/10.1128/iai.67.10.5455-5462.1999.
Full textAbstract:
ABSTRACT The complete nucleotide sequence and organization of the enteropathogenic Escherichia coli (EPEC) adherence factor (EAF) plasmid of EPEC strain B171 (O111:NM) were determined. The EAF plasmid encodes two known virulence-related operons, thebfp operon, which is composed of genes necessary for biosynthesis of bundle-forming pili, and the bfpTVW(perABC) operon, composed of regulatory genes required forbfp transcription and also for transcriptional activation of the eae gene in the LEE pathogenicity island on the EPEC chromosome. The 69-kb EAF plasmid, henceforth designated pB171, contains, besides the bfp and bfpTVW(perABC) operons, potential virulence-associated genes, plasmid replication and maintenance genes, and many insertion sequence elements. Of the newly identified open reading frames (ORFs), two which comprise a single operon had the potential to encode proteins with high similarity to a C-terminal region of ToxB whose coding sequence is located on pO157, a large plasmid harbored by enterohemorrhagicE. coli. Another ORF, located between the bfpand bfpTVW operons, showed high similarity withtrcA, a bfpT-regulated chaperone-like protein gene of EPEC. Two sites were found to be putative replication regions: one similar to RepFIIA of p307 or F, and the other similar to RepFIB of R100 (NR1). In addition, we identified a third region that contains plasmid maintenance genes. Insertion elements were scattered throughout the plasmid, indicating the mosaic nature of the EAF plasmid and suggesting evolutionary events by which virulence genes may have been obtained.
6
Mole, Beth, Sohrab Habibi, Jeffery L. Dangl, and Sarah R. Grant. "Gluconate Metabolism Is Required for Virulence of the Soft-Rot Pathogen Pectobacterium carotovorum." Molecular Plant-Microbe Interactions® 23, no. 10 (October 2010): 1335–44. http://dx.doi.org/10.1094/mpmi-03-10-0067.
Full textAbstract:
Pectobacterium carotovorum is a ubiquitous soft rot pathogen that uses global virulence regulators to coordinate pathogenesis in response to undefined environmental conditions. We characterize an operon in P. carotovorum required for gluconate metabolism and virulence. The operon contains four genes that are highly conserved among proteobacteria (initially annotated ygbJKLM), one of which was misassigned as a type III secreted effector, (ygbK, originally known as hopAN1). A mutant with a deletion-insertion within this operon is unable to metabolize gluconate, a precursor for the pentose phosphate pathway. The mutant exhibits attenuated growth on the leaves of its host of isolation, potato, and those of Arabidopsis thaliana. Notably, the mutant hypermacerates potato tubers and is deficient in motility. Global virulence regulators that are responsive to cell wall pectin breakdown products and other undefined environmental signals, KdgR and FlhD, respectively, are misregulated in the mutant. The alteration of virulence mediated via changes in transcription of known global virulence regulators in our ygbJ-M operon mutant suggests a role for host-derived catabolic intermediates in P. carotovorum pathogenesis. Thus, we rename this operon in P. carotovorum vguABCD for virulence and gluconate metabolism.
7
Vu-Khac, Hung, and Kurt W. Miller. "Regulation of Mannose Phosphotransferase System Permease and Virulence Gene Expression in Listeria monocytogenes by the EIItMan Transporter." Applied and Environmental Microbiology 75, no. 21 (September 4, 2009): 6671–78. http://dx.doi.org/10.1128/aem.01104-09.
Full textAbstract:
ABSTRACT The EIIt Man phosphotransferase system (PTS) permease encoded by the mpt operon is the principal glucose transporter in Listeria monocytogenes. EIIt Man participates in glucose-mediated carbon catabolite repression (CCR) and downregulation of virulence gene expression, and it is the receptor for class IIa bacteriocins. The regulation of this important protein and its roles in gene control were examined using derivatives of strain EGD-e in which the mpt operon or its regulatory genes, manR and lmo0095, were deleted. Real-time reverse transcription-PCR analysis showed that the mpt mRNA level was 10- and 100-fold lower in the lmo0095 and manR deletion strains, respectively. The manR mRNA level was higher in the mpt deletion mutant in medium lacking glucose, possibly due to disruption of a regulatory process that normally downregulates manR transcription in the absence of this sugar. Analysis of the mpt deletion mutant also showed that EIIt Man participates to various degrees in glucose-mediated CCR of PTS operons. CCR of the lmo0027 gene, which encodes a β-glucoside PTS transporter, required expression of EIIt Man. In contrast, genes in two mannose PTS operons (lmo0024, lmo1997, and lmo2002) were repressed by glucose even when EIIt Man was not synthesized. A third mannose PTS operon, mpo, was not regulated by glucose or by the level of EIIt Man. Finally, the mRNA levels for five genes in the prfA virulence gene cluster were two- to fourfold higher in the mpt deletion mutant. The results show that EIIt Man participates to various extents in glucose-mediated CCR of PTS operons and makes a small, albeit significant, contribution to downregulation of virulence gene transcription by glucose in strain EGD-e.
8
Onasanya, Amos, R. O. Onasanya, Abiodun A. Ojo, and B. O. Adewale. "Genetic Analysis and Molecular Identification of Virulence in Xanthomonas oryzae pv. oryzae Isolates." ISRN Molecular Biology 2013 (September 8, 2013): 1–8. http://dx.doi.org/10.1155/2013/160157.
Full textAbstract:
Bacterial leaf blight (BLB) of rice is a very destructive disease worldwide and is caused by Xanthomonas oryzae pv. oryzae (Xoo). The aim of the present study was to examine if the Xoo virulence pathotypes obtained using phenotypic pathotyping could be confirmed using molecular approach. After screening of 60 Operon primers with genomic DNA of two Xoo isolates (virulent pathotype, Vr, and mildly virulent pathotype, MVr), 12 Operon primers that gave reproducible and useful genetic information were selected and used to analyze 50 Xoo isolates from 7 West African countries. Genetic analysis revealed two major Xoo virulence genotypes (Mta and Mtb) with Mta having two subgroups (Mta1 and Mta2). Mta1 (Vr1) subgroup genotype has occurrence in six countries and Mta2 (Vr2) in three countries while Mtb genotype characterized mildly virulence (MVr) Xoo isolates present in five countries. The study revealed possible linkage and correlation between phenotypic pathotyping and molecular typing of Xoo virulence. Xoo virulence genotypes were known to exist within country and there was evidence of Xoo pathogen migration between countries. Durable resistance rice cultivars would need to overcome both Mta and Mtb Xoo virulence genotypes in order to survive after their deployment into different rice ecologies in West Africa.
9
Wright, Anita C., Jan L. Powell, James B. Kaper, and J. Glenn Morris. "Identification of a Group 1-Like Capsular Polysaccharide Operon for Vibrio vulnificus." Infection and Immunity 69, no. 11 (November 1, 2001): 6893–901. http://dx.doi.org/10.1128/iai.69.11.6893-6901.2001.
Full textAbstract:
ABSTRACT Virulence of Vibrio vulnificus correlates with changes in colony morphology that are indicative of a reversible phase variation for expression of capsular polysaccharide (CPS). Encapsulated variants are virulent with opaque colonies, whereas phase variants with reduced CPS expression are attenuated and are translucent. Using TnphoA mutagenesis, we identified a V.vulnificus CPS locus, which included an upstreamops element, a wza gene (wza Vv), and several open reading frames with homology to CPS biosynthetic genes. This genetic organization is characteristic of group 1 CPS operons. The wzagene product is required for transport of CPS to the cell surface inEscherichia coli. Polar transposon mutations inwza Vv eliminated expression of downstream biosynthetic genes, confirming operon structure. On the other hand, nonpolar inactivation of wza Vv was specific for CPS transport, did not alter CPS biosynthesis, and could be complemented in trans. Southern analysis of CPS phase variants revealed deletions or rearrangements at this locus. A survey of environmental isolates indicated a correlation between deletions inwza Vv and loss of virulent phenotype, suggesting a genetic mechanism for CPS phase variation. Full virulence in mice required surface expression of CPS and supported the essential role of capsule in the pathogenesis of V.vulnificus.
10
O’Neill, Erinn M., Tatiana S. Mucyn, Jon B. Patteson, Omri M. Finkel, Eui-Hwan Chung, Joshua A. Baccile, Elisabetta Massolo, Frank C. Schroeder, Jeffery L. Dangl, and Bo Li. "Phevamine A, a small molecule that suppresses plant immune responses." Proceedings of the National Academy of Sciences 115, no. 41 (September 20, 2018): E9514—E9522. http://dx.doi.org/10.1073/pnas.1803779115.
Full textAbstract:
Bacterial plant pathogens cause significant crop damage worldwide. They invade plant cells by producing a variety of virulence factors, including small-molecule toxins and phytohormone mimics. Virulence of the model pathogen Pseudomonas syringae pv. tomato DC3000 (Pto) is regulated in part by the sigma factor HrpL. Our study of the HrpL regulon identified an uncharacterized, three-gene operon in Pto that is controlled by HrpL and related to the Erwinia hrp-associated systemic virulence (hsv) operon. Here, we demonstrate that the hsv operon contributes to the virulence of Pto on Arabidopsis thaliana and suppresses bacteria-induced immune responses. We show that the hsv-encoded enzymes in Pto synthesize a small molecule, phevamine A. This molecule consists of l-phenylalanine, l-valine, and a modified spermidine, and is different from known small molecules produced by phytopathogens. We show that phevamine A suppresses a potentiation effect of spermidine and l-arginine on the reactive oxygen species burst generated upon recognition of bacterial flagellin. The hsv operon is found in the genomes of divergent bacterial genera, including ∼37% of P. syringae genomes, suggesting that phevamine A is a widely distributed virulence factor in phytopathogens. Our work identifies a small-molecule virulence factor and reveals a mechanism by which bacterial pathogens overcome plant defense. This work highlights the power of omics approaches in identifying important small molecules in bacteria–host interactions.
Dissertations / Theses on the topic "Virulence Operon"
1
Zorgani, Mohamed Amine. "Caractérisation des ARN régulateurs chez Streptococcus agalactiae." Thesis, Tours, 2016. http://www.theses.fr/2016TOUR3309.
Full textAbstract:
Streptococcus agalactiae, appelé aussi Group B Streptococcus (GBS), est une bactérie commensale du tractus digestif et génital de diverses espèces animales dont l’espèce humaine. Elle représente la première cause d’infections néonatales et est aussi un pathogène émergent chez l’adulte immunodéprimé. L’objectif de ma thèse est la caractérisation fonctionnelle et mécanistique des ARNrég. J’ai étudié plus particulièrement l’ARNrég CetR (pour «cell-envelope-targeting RNA»). Il module la résistance au peptide antimicrobiens (PAM) et la virulence à travers la régulation post-transcriptionnelle de l’ARNm dltD codant une protéine de biosynthèse de l'acide D-alanyl-lipotéichoïque. La délétion de cetR induit des changements dans la morphologie cellulaire, une diminution de la formation du biofilm et de la résistance aux PAM. Une zone d’interaction, CetRdltD, de 27 nucléotides a été prédite in silico. Des mutations compensatoires chez GBS montrent que CetR interagit directement avec l’ARNm dltD et que la perturbation de la zone d’appariement est suffisante pour observer les phénotypes associés à CetR. La quantification des niveaux d’ARNm et de la protéine DltD nous a permis de montrer que CetR active la traduction de dltD et que la perturbation du duplex CetR-dltD induit une diminution spectaculaire de la protéine DltD. De plus, en utilisant un modèle murin d’infection et en quantifiant la survie des bactéries dans les macrophages, nous avons montré que CetR et DltD sont cruciaux pour la virulence de GBS. Enfin, une approche protéomique globale nous a permis de montrer que CetR joue un rôle important dans l’expression des protéines dites « moonlighting » et de certains facteurs de virulence potentiels. Cet ARNrég peut jouer un rôle important dans la capacité de S. agalactiae à s'établir dans son biotope et à exprimer ses facteurs de virulence. Enfin, les résultats de ces recherches sont des prérequis au développement de stratégies permettant de réduire le risque des infections néonatales dues à S. agalactiaeThe opportunistic pathogen group B Streptococcus (GBS) is the leading cause of neonatal infections. The aim of this work is the characterization of a 680 nt-long regulatory RNA, CetR (cell-envelope-targeting RNA). It modulates antimicrobial peptides (AMPs) resistance and virulence through posttranscriptional regulation of dltD mRNA which encodes a D-alanyl-lipoteichoic acid biosynthesis protein. Deletion of cetR leads to cell morphology changes, reduced biofilm formation and AMPs resistance. A 27 nt-long CetR-dltD interacting region is predicted in silico. Compensatory base pair exchanges in GBS demonstrate that CetR interacts directly with dltD mRNA and that disruption of this RNA pairing is sufficient to observe the CetR-associated phenotypes. By quantifying both mRNA and protein, we demonstrate that CetR enhances dltD translation and disruption of the CetR/dltD mRNA interaction results in a dramatic decrease in DltD protein. Moreover, using an infection murine model and quantifying bacterial survival in macrophages, we observe that both CetR and DltD are crucial for GBS virulence. Finally, we highlight CetR pleiotropic role in the expression of several moonlighting proteins and potential virulence factors. This regulatory RNA may play an important role in the ability of GBS to settle in its biotope and express its virulence factors
2
Franza, Thierry, and ANDRE KLIER. "Caracterisation d'un nouvel operon intervenant dans le transport et la biosynthese de la chrysobactine, siderophore implique dans la virulence d'une enterobacterie phytopathogene erwinia chrysanthemi." Paris 7, 1991. http://www.theses.fr/1991PA077233.
Full textAbstract:
Pour induire une reponse systemique sur son hote, saintpaulia ionantha, la souche 3937 d'erwinia chrysanthemi requiert un systeme d'assimilation du fer a haute affinite totalement fonctionnel. Ce systeme se caracterise par la production d'un siderophore de type catechol, la chrysobactine et une proteine de membrane externe, appelee fct, reconnaissant specifiquement la ferrichrysobactine. La synthese de la chrysobactine commence par la conversion du chorismate en acide 2,3-dihydroxybenzoique (dhba), qui est alors active avant condensation avec le dipeptide d-lysyl-l-serine. Les quatre premieres etapes de cette biosynthese sont identiques a celles de la synthese du siderophore enterobactine d'escherichia coli. Des experiences de clonage et de complementation fonctionnelle ont permis de sous-cloner le systeme chrysobactine chez e. Coli. Le gene de transport fct et les genes cbs impliques dans la production et l'activation du dhba sont regroupes dans un operon de 8 kb environ dans l'ordre suivant: fct, cbsc, cbse, cbsb et cbsa
3
Toukoki, Chadia. "MTSR is a Dual Regulator that Controls Virulence Genes and Metabolic Functions in Addition to Metal Homeostasis in Group A Streptococcus." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/biology_diss/66.
Full textAbstract:
Group A Streptococcus (GAS) is a common pathogen of the human skin and mucosal surfaces and is capable of producing a variety of diseases. This dissertation investigates the function of a metalloregulator named MtsR in GAS physiology and disease process. An mtsR mutant was constructed and analyzed. Consistent with MtsR role in iron uptake regulation, the mtsR mutant accumulates more iron (80 ± 22.5%) than the wild type strain. Inactivation of mtsR results in constitutive transcription of the sia (Streptococcal Iron Acquisition) operon, which is negatively regulated by iron in the parent strain. We identified the promoter that controls the expression of the sia operon (Pshr) and used it as a model to study MtsR interaction with DNA. Electrophoretic mobility gel shift assays (EMSAs) demonstrated that MtsR binds to the shr upstream region specifically and in an iron and manganese dependent manner. DNase I footprint analysis revealed that MtsR protects a 69 bp segment in Pshr that includes 2 inverted repeats, overlapping the core promoter elements. A global transcriptional analysis determined that MtsR modulates the expression of 64 genes, of which 44 were upregulated and 20 were downregulated in the mtsR mutant. MtsR controls genes with diverse functions including immune evasion, colonization, dissemination, metal homeostasis, nucleic acid and amino acid metabolism, and protein stability. MtsR functions as a dual regulator as it binds to the promoters of the repressed genes ska, aroE, and nrdF.2, as well as the upstream region of the positively regulated genes mga, emm49, and pyrF. A 16 bp MtsR-binding consensus region was identified in all of the promoters that are directly regulated by MtsR. In conclusion, we have demonstrated that MtsR is a global regulator in GAS that controls the expression of vital virulence factors and genes involved in metal transport, virulence and metabolic pathways.
4
Bernardi, Adilson César Abreu [UNESP]. "Estudo de amostras de Staphylococcus coagulase-negativa quanto a formação de biofilme." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/103991.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:32:55Z (GMT). No. of bitstreams: 0
Previous issue date: 2005-12-13Bitstream added on 2014-06-13T19:22:47Z : No. of bitstreams: 1
bernardi_aca_dr_arafcf.pdf: 1525508 bytes, checksum: c65f0bdce77e95dac615f5ee33dd6287 (MD5)Universidade Estadual Paulista (UNESP)
Os Staphylococcus coagulase-negativa, particularmente, os Staphylococcus epidermidis são a causa mais freqüente de infecções relacionadas ao cateter por sua habilidade em aderir a uma superfície e entre si (aderência intercelular) formando biofilme em multicamadas sobre superfícies de polímeros. O objetivo do presente estudo foi avaliar cepas hospitalares de Staphylococcus coagulasenegativa isoladas de cateteres intravenosos, quanto à resistência a oxacilina, produção de slime, aderência ao poliestireno, habilidade de formar biofilme sobre superfícies abióticas (cateter esterilizado) e a presença de genes icaAD. Na presente pesquisa, a presença de icaA e icaD foi determinada pelo método PCR, em uma coleção de 27 amostras Staphylococcus coagulase-negativa (10 Staphylococcus epidermidis, 4 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi, 2 S. xylosus e 4 S. warneri). Os genes icaAD foram detectados em dez cepas S. epidermidis...
Coagulase-negative Staphylococcus, particularly, Staphylococcus epidermidis are frequent cause of infections associated with catheters and is attributed to the attachment ability on a surface and each other (intercellular adhesion) forming a multilayered biofilm on polymeric surfaces. The objective of the present study was to evaluate coagulase-negative Staphylococcus strains isolated from intravenous catheters by oxacillin resistance, slime production (qualitative method) and spectrophotometric assay (quantitative method), ability to form biofilm on abiotic surfaces (steriled catheter) and the presence of icaAD genes. In the present study icaA and icaD were determined by PCR method, in a collection of 27 coagulasenegative Staphylococcus (10 Staphylococcus epidermidis, 4 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi, 2 S. xylosus and 4 S. warneri). The icaA genes were detected in nine S. epidermidis and icaD in ten. The slime-producing ability was determined by culture on Congo red agar plates in which slime-producing strains formed black colonies in 10 S. epidermidis, 4 S.haemolyticus, 4 S. warneri, 2 S. xylosus and 1 S. chromogenes, while nonslimeformingones develop red colonies. The quantitative assay of coagulase-negative Staphylococcus was observed in 19 strains, including: 10 S. epidermidis, 3 S.haemolyticus, 3 S. warneri, 2 S. xylosus, 1 S. chromogenes. The ability of coagulasenegative Staphylococcus to form biofilm embedded in an amorphous substance wasobserved by scanning electronic microscope on abiotic surface in 10 S. epidermidis,3 S. haemolyticus, 2 S. hominis, 2 S. lugdunensis, 1 S. saprophyticus, 1 S. schleiferi,2 S. xylosus and 3 S. warneri. The oxacillin resistance was observed in 9 strains S.epidermidis, 3 S. haemolyticus, 3 S. warneri, 1 S. xylosus and 1 S. chromogenes. All strains of staphylococci were susceptible... (Complete abstract, click eletronic address below)
5
Silva, Filho Renato Geraldo da. "Produção de biofilme em amostras clínicas de S. epidermidis: influência de concentrações subinibitórias de antissépticos (etanol e clorexidina) e associação com potenciais marcadores de virulência." reponame:Repositório Institucional da FIOCRUZ, 2014. https://www.arca.fiocruz.br/handle/icict/10997.
Full textAbstract:
Submitted by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-06-29T12:53:56Z
No. of bitstreams: 1
Tese_Renato_Silva.pdf: 1149696 bytes, checksum: 90cca601f940d32033deeaeb17255312 (MD5)Approved for entry into archive by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-06-29T12:54:09Z (GMT) No. of bitstreams: 1 Tese_Renato_Silva.pdf: 1149696 bytes, checksum: 90cca601f940d32033deeaeb17255312 (MD5)
Approved for entry into archive by Alexandre Sousa (alexandre.sousa@incqs.fiocruz.br) on 2015-06-29T12:54:23Z (GMT) No. of bitstreams: 1 Tese_Renato_Silva.pdf: 1149696 bytes, checksum: 90cca601f940d32033deeaeb17255312 (MD5)
Made available in DSpace on 2015-06-29T12:54:23Z (GMT). No. of bitstreams: 1 Tese_Renato_Silva.pdf: 1149696 bytes, checksum: 90cca601f940d32033deeaeb17255312 (MD5) Previous issue date: 2014
Fundação Oswaldo Cruz. Instituto Nacional de Controle de Qualidade em Saúde
S. epidermidis é o principal agente de infecções associadas a dispositivos médicos implantados, sendo sua habilidade para formar biofilme em superfícies inertes o fator determinante para a persistência desse micro-organismo. Neste estudo avaliamos 52 isolados clínicos desta espécie quanto à susceptibilidade a antimicrobianos, produção de biofilme/natureza química, presença de genes relacionados à virulência (atlE, capB,aap, embp, bhp, IS256 e IS257), e o efeito de concentrações subinibitórias (sub-CIMs) de etanol e clorexidina na produção de biofilme. Além disso, algumas das amostras biofilme-positivas foram estudadas quanto ao efeito de sub-CIMs destes antissépticos na expressão de icaA, icaR, sigB e sarA. Mais de 60% das amostras apresentaram resistência para ≥ 10 drogas e as amostras produtoras de biofilme mostraram, no geral, maior percentual de resistência a antimicrobianos. No teste em placa de microtitulação (MTP), 23 amostras foram produtoras de biofilme, sendo 14 de natureza polissacarídica, 8 proteica e 3 indeterminada. No teste em Ágar Vermelho Congo, somente amostras produtoras de biofilme polissacarídico apresentaram reação positiva. Genes do operon ica foram detectados em 23 isolados, sendo 17 destes classificados como produtores e 6 como não produtores de biofilme no MTP. A frequência dos outros genes relacionados à produção de biofilme foi: embp (69%), aap (29%) e bhp (12%), não sendo detectada correlação entre estes e a produção de biofilme do tipo PIA-independente. Os genes aap (29%) e IS256 (23%) mostraram correlações significativas com: produção de biofilme, presença de ica, perfil biofilme+/ica+, e produção de nível forte de biofilme. O gene IS256 foi ainda correlacionado significativamente com resistência a alguns antimicrobianos. Sub-CIMs de etanol (2 e/ou 4%) determinaram aumento na produção de biofilme em 15 das 17 amostras PIA-dependentes e nas 8 PIA-independentes, mas não induziram produção de biofilme em amostras originalmente não produtoras. Ao contrário do etanol, sub-CIMs de clorexidina não somente não induziram produção, como determinaram redução da produção de biofilme nas amostras biofilme-positivas. Nas amostras PIA-dependentes, o etanol (1%) acarretou aumento da expressão relativa de icaA e redução da expressão de icaR, além de aumento da expressão dos reguladores globais (sarA e sigB), enquanto a amostra PIA-independente mostrou redução na expressão destes reguladores globais. Ao contrário do etanol, a clorexidina (0,5 μg/mL) determinou aumento da expressão de icaR e redução de icaAnas amostras PIA-dependentes, além de redução na expressão de sarA e sigB na amostra PIA-independente. Os resultados indicaram que a produção de biofilme mostrou-se associada com alguns dos potenciais marcadores de virulência, sendo também evidenciada associação de alguns desses marcadores com resistência a certos antimicrobianos. As amostras PIA-dependentes foram prevalentes, destacando-se, porém, o encontro de número expressivo de amostras PIA-independentes. Os genes aap,embp e bhp não se mostraram correlacionados com a produção de biofilme proteico, indicando existência de outros mecanismos envolvidos na formação desse tipo de biofilme. Nas amostras PIA-dependentes, etanol e clorexidina mostraram efeitos opostos na expressão de icaA e icaR, corroborando dados fenotípicos previamente obtidos, e enfatizando a necessidade de ampliação do estudo da clorexidina, tendo em vista o potencial de aplicação prática deste achado.
S. epidermidis is the main agent of infections associated with implanted medical devices, being its ability to form biofilms on inert surfaces the determinant factor for the persistence of this microorganism. Fifth two clinical isolates of this species were evaluated for susceptibility to antimicrobials, biofilm production/chemical nature, presence of genes related to virulence (atlE, capB, aap, embp, bhp, IS256 andIS257), and the effect of subinibitory concentrations (sub-MICs) of ethanol and chlorhexidine in biofilm production. Moreover, some of biofilm-positive samples were studied for the effect of sub-MICs of these antiseptics in the expression of icaA, icaR, sigB and sarA. Over 60% of the samples showed resistance to ≥ 10 drugs and biofilm producers showed, in general, a higher percentage of antimicrobial resistance. In microtiter plate test (MTP), 23 strains were biofilm producers, being 4 of polysaccharide nature, 8 proteinaceous and 3 undetermined. In Congo Red Agar test, only biofilm polysaccharide producer strains showed a positive reaction. ica operon genes were detected in 23 isolates, being 17 of these classified as producers and 6 as non-biofilm producers in MTP. The frequency of other production-related biofilm genes was: embp (69%), aap (29%) and bhp (12%), no being detect a correlation between them and the production of PIA-independent biofilm. The aap (29%) and IS256 (23%) genes showed significant correlations with: biofilm production, presence of ica biofilm, biofilm+/ica+ profile, and strong level of production of biofilm. The IS256 gene was also significantly correlated with resistance to some antibiotics. Sub-MIC of ethanol (2 and / or 4%) led to an increase in biofilm production in 15 of 17 samples PIA-dependent and in the 8 PIA-independent, but did not induce biofilm production in not originally producing samples. Unlike ethanol, sub-MICs of chlorhexidine not only did not induce production as determined reduction of biofilm production in biofilm-positive samples. In PIA-dependent strains, ethanol (1%) caused an increase in the relative expression of icaAand reduced expression of icaR, in addition to increased expression of global regulators (sarA and sigB), while the PIA-independent strain showed reduction in the expression of these global regulators. Unlike ethanol, chlorhexidine (0.5 mg/mL) determined increased expression of icaR and reduction of icaA in PIA-dependent strains, besides a reduction in the expression of sarA and sigB in the PIA-independent strain. The results indicated that biofilm production was associated with some of potential virulence markers, and also evidenced some combination of these markers and resistance to certain antibiotics. The PIA-dependent strains were prevalent, highlighting, however, the encounter of significant number of PIA-independent strains. The aap, embp and bhp genes were not correlated with the production of proteinaceous biofilm, indicating the existence of other mechanisms involved in the formation of such biofilms. In PIA-dependent strains, ethanol and chlorhexidine showed opposite effects on the expression of icaA and icaR, corroborating phenotypic data previously obtained, and emphasizing the need to expand the study of chlorhexidine, in view of the potential of practical application of this finding.
6
Kamar, Rita. "Mécanismes de résistance aux peptides antimicrobiens chez Bacillus thuringiensis : rôle de dltX dans la D-alanylation des acides téichoïques." Electronic Thesis or Diss., Paris, AgroParisTech, 2014. http://www.theses.fr/2014AGPT0029.
Full textAbstract:
Le groupe Bacillus cereus est très hétérogène du point de vue toxicité et il est difficile de prédire le potentiel pathogène d'une souche. Dans ce travail, nous avons étudié les différents phénotypes de colonisation/adaptation à l'hôte, et analysé la corrélation entre ces phénotypes et les maladies humaines, pour une collection de souches représentatives de la diversité pathologique de B. cereus chez l'homme. L'analyse statistique a révélé des corrélations entre plusieurs phénotypes, et une analyse en composante principale a permis de regrouper les souches en deux sous-populations distinctes. Notre étude a ainsi permis de montrer qu'un ensemble de caractères phénotypiques liés au pouvoir pathogène permet de discriminer les souches présentant un historique en maladies infectieuses des souches sans historique. Nous pensons que ces résultats faciliteront l'identification d'un phénotype ou d’une combinaison de phénotypes qui pourraient être utilisés dans le développement de stratégies de prévention des infections par B. cereus. Le résultat de cette étude suggère que B. cereus n'est pas exclusivement un pathogène opportuniste et pourrait plutôt être considéré comme un véritable agent pathogène en soi.Cependant, la virulence est un phénomène multifactoriel impliquant de nombreux facteurs du côté de l'hôte ainsi que de celui de l'agent pathogène envahisseur. Les peptides antimicrobiens (PAMs) cationiques constituent les principales molécules effectrices de l’immunité innée. La résistance des microorganismes vis à vis de ces composés est donc nécessaire pour qu’ils puissent se développer dans l’hôte et exercer leur pouvoir pathogène. Par conséquent, de nombreuses bactéries pathogènes ont développé des stratégies de résistance impliquant la réduction des charges négatives de l’enveloppe bactérienne, réduisant ainsi l'interaction et la fixation de ces PAMs. L'incorporation de résidus D-alanine aux acides téichoïques (ATs) représente l'un des mécanismes les plus courants de résistance bactérienne qui dépendent de telles modifications. Ce processus de D-alanylation est accompli par les produits des gènes de l’opéron dlt. Celui-ci contient cinq gènes dltXABCD dont les séquences sont très conservées dans la quasi-totalité des bactéries à Gram-positif. La première ORF, dltX, code pour une protéine dont la fonction est inconnue. Le but de la seconde partie de ce travail était donc de déterminer si cette protéine est impliquée dans le processus de D-alanylation chez Bacillus thuringiensis. Pour cela, nous avons procédé à une délétion en phase du gène dltX, qui n’affecte pas l’expression des autres gènes de l'opéron. Les caractéristiques de croissance du mutant dltX et celles de la souche de type sauvage se sont avérées similaires in vitro. Cependant la délétion de dltX affecte considérablement la résistance de B. thuringiensis aux PAMs et atténue significativement sa virulence chez deux espèces d’insectes: Galleria mellonella et Drosophila melanogaster. En outre, une analyse HPLC montre que la paroie du mutant dltX est dépourvue de D-alanine, et la mesure de la mobilité électrophorétique indique que cette absence de D-alanylation est associée à un changement de la charge globale à la surface bactérienne. Des expériences de microscopie électronique à balayage montrent aussi des modifications morphologiques du mutant dltX, ce qui suggère que l'absence de D-alanine affecte également la structure de la paroi cellulaire. Nos résultats montrent que DltX est essentiel pour l'incorporation de la D-alanine aux acides téichoïques. Par ailleurs nous avons également démontré que dltX n’affecte pas l’expression de l’opéron dlt. Par conséquent nos résultats indiquent clairement que DltX joue un rôle direct dans la résistance aux PAMs, contribuant ainsi à la survie et la virulence de B. thuringiensis chez les insectes. Ce travail est le premier qui étudie la participation de dltX dans la D-alanylation des ATsThe Bacillus cereus pathogenic spectrum ranges from strains used as probiotics to human-lethal strains (causing gastrointestinal disorders or local and severe systemic infections). However, prediction of the pathogenic potential of a strain remains difficult. In this work, we studied different phenotypes of colonization/adaptation to the host (adhesion, cytotoxicity, motility, biofilm formation, resistance to antimicrobial peptides and virulence), analyzing the correlation between these phenotypes and human disease in a collection of strains representative of the pathological diversity of B. cereus in humans. Statistical analysis revealed correlations between several phenotypes, and principal component analysis grouped the strains into two distinct subpopulations. We found that strains differed in pathogenic potential and that virulent strains could be differentiated from non-pathogenic strains. We believe that these findings will facilitate the identification of a phenotype or a combination of phenotypes of potential use in the development of effective prevention strategies and/or diagnostic tools for distinguishing between pathogenic and non-pathogenic B. cereus strains. Our result suggests that B. cereus is not an exclusively opportunistic pathogen and could instead be considered a real pathogen per se. However, virulence is a multifactorial phenomenon involving numerous factors from both the host and the invading pathogen. As cationic antimicrobial peptides (CAMPs) are the primary defense mechanism against invading organisms, virulence of pathogens like B. cereus requires bacterial resistance to such compounds. Consequently, many pathogens have developed resistance strategies involving the reduction of the cell envelope negative charge, thereby influencing the binding and interaction of these CAMPs. The incorporation of Dalanine esters into teichoic acids (TAs) represents one of the most common bacterial resistance mechanisms that depend on such charge modifications. That D-alanylation process is accomplished by the gene products of an operon containing five genes, dltXABCD, that is highly conserved among nearly all gram-positive bacteria. The small first ORF, dltX, encodes a protein of unknown function. The aim of the other part of this work was then to establish whether this protein is involved in the D-alanylation process in Bacillus thuringiensis. We therefore constructed an in frame deletion mutant of dltX, without affecting the expression of the other genes of the operon. The growth characteristics of the dltX mutant and those of the wild type strain were similar under standard in vitro conditions. However disruption of dltX drastically impaired the resistance of B. thuringiensis to CAMPs and significantly attenuated its virulence in two insect species: Galleria mellonella and Drosophila melanogaster. Moreover, HPLC studies showed the dltX mutant was devoid of D-alanine, and electrophoretic mobility measurements indicated that the cells carried a higher negative surface charge. Scanning electron microscopy experiments showed morphological alterations of these mutant bacteria, suggesting that depletion of D-alanine from TAs affects cell wall structure. Our findings suggest that DltX is essential for the incorporation of D-alanyl esters into teichoic acids. Moreover, we found that DltX does not affect the expression of the operon. We therefore conclude that dltX is translated into a functional protein that plays a direct biosynthetic, transport or addresser role. Altogether, our results clearly indicate that DltX plays a direct role in the resistance to CAMPs, thus contributing to the survival and virulence of B. thuringiensis in insects. The exact function of that protein remains to be elucidated. This work is the first report examining the involvement of dltX in the Dalanylation of TAs
7
Azuama, Onyedikachi Cecil. "Recherche de nouveaux actifs d'origine végétale contre le pathogène opportuniste de l'homme Pseudomonas aeruginosa Battling Pseudomonas aeruginosa virulence with natural plant bioactive compounds Membrane-interactive compounds from Pistacia lentiscus L. thwart Pseudomonas aeruginosa virulence Tackling Pseudomonas aeruginosa virulence by mulinane-like diterpenoids from Azorella atacamensis Pseudomonas aeruginosa virulence attenuation by extracts of Parastrephia terestiuscula, Baccharis grisebachii, Haplopappus rigidus medicinal plants of the Asteraceae family from the Atacama Desert area The absence of SigX results in impaired carbon metabolism and membrane fluidity in Pseudomonas aeruginosa Activation of the Cell Wall stress response in Pseudomonas aeruginosa infected by a Pf4 Phage Variant The temperature-regulation of Pseudomonas aeruginosa cmaX-cfrX-cmp-X operon reveals an intriguing molecular network involving the Sigma factors AlgU and SigX." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR077.
Full textAbstract:
La résistance aux antimicrobiens est l’un des défis majeurs du XX1eme siècle. Pseudomonas aeruginosa est inscrit sur la liste des organismes pathogènes qui deviennent résistants aux antibiotiques conventionnels. De nouvelles stratégies visant à atténuer la virulence sans perturber la croissance et la viabilité bactériennes, également connues sous le nom de stratégie anti-virulence, sont développées. Les plantes sont connues pour produire de nombreux métabolites secondaires. Des extraits de fruits de Pistachia Lentiscus originaires d'Algérie et de 40 extraits de plantes originaires du Nord-Chili ont été criblés pour leur capacité à atténuer la production de la pyocyanine, un facteur de virulence majeur de P. aeruginosa, dans le but d’évaluer leur potentiel effet antivirulence. Les extraits sélectionnés (Pistacia lentiscus, Azorella atacamensis, Baccharis grisebachii, Haplopappus rigidus et Parastrephia terestiucula), ont été fractionnés et l’ensemble de ces extraits et fractions a montré une atténuation de la production d’autres facteurs de virulence (élastase, rhamnolipides), qui a pu être attribuée, au moins partiellement à une diminution de la communication bactérienne via le mécanisme du quorum sensing. Ces extraits et fractions altèrent également la fluidité membranaire de P. aeruginosa. Cet effet anti-virulence a été validé dans un modèle d'infection cellulaire, et sur le nématode Caenorhabditis elegans. Dans toutes ces conditions, la croissance de P. aeruginosa n'a pas été affectée. Un profilage chimique des extraits et fractions de P. lentiscus et d'A atacamensis a révélé la présence d'acide gingkolique et de diterpenoides de type azorellane/mulinane comme potentiels composés bioactifs. De futures études visent à identifier les composés bioactifs sur P. aeruginosa H103, ainsi que sur un panel de souches cliniques, et à évaluer un potentiel effet potentialisateur de l'activité des antibiotiques. Ces travaux visent in fine à proposer ces composés d’origine végétale comme adjuvants dans le traitement des infections à P. aeruginosaAntimicrobial resistance has become a great challenge in therapeutic medicine so much so that the World health organization forecasts the possibility of a post-antibiotic era where minor injuries may lead to mortality. Pseudomonas aeruginosa is among the list of organisms that are highly resistant to conventional antibiotics, partly due to its broad genome, which facilitates the elaboration of virulence determinants and rapid adaptation to various environments, in addition to its inherent resistance mechanisms. In view of this, alternative measures of controlling microbial virulence activities using novel approaches that do not disturb its growth and viability, also known as anti-virulence strategy, are gaining wider attention. Since plants are repositories of several metabolites with chemical defense system against environmental pathogens, through ethnobotanical led studies, the effect of Pistacia lentiscus fruit extracts originating from Algeria and forty plant extracts originating from North-Chile were biologically and chemically evaluated with the aim of deciphering their anti-virulence effects against P. aeruginosa. Furthermore, this study tried to gain more insight into the bioactive compounds and possible mechanism of action. From the results obtained, selected plant extracts attenuated P. aeruginosa mainly pyocyanin activity and /or elastase and rhamnolipids virulence production which appears to be associated with the inhibition of quorum sensing activities and the alteration in membrane activities. The anti-virulence effect of the selected extracts (P. lentiscus, Azorella atacamensis, Baccharis grisebachii, Haplopappus rigidus and Parastrephia terestiucula) were also validated in biological models of infections where they mediated the toxicity of P. aeruginosa towards A549 human monolayer cells and/or Caenorhabditis elegans nematode. Interestingly, growth of the pathogen was not affected. Further chemical profiling of P. Lentiscus, and A atacamensis extracts revealed the presence of gingkolic acid and azorellane/mulinane diterpenoids as the putative bioactive compounds. Future studies intend to explore these extracts and their derived compounds on the potentiation of antibiotic activity in a panel of clinical strains. In general, this study sets the pace for the possible use of these plant extracts as adjuvants in treatment of P. aeruginosa infections
8
Tortuel, Damien. "Vers la compréhension du rôle de SigX dans la réponse au stress de l'enveloppe chez Pseudomonas aeruginosa Pf4 phage infection induces SOS and cell envelope stress responses in Pseudomonas aeruginosa Pf4 phage infection reduced virulence-associated phenotypes in Pseudomonas aeruginosa The temperature-regulation of Pseudomonas aeruginosa cmaX-cfrX-cmpX operon reveals an intriguing molecular network involving the sigma factors AlgU and SigX." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMR002.
Full textAbstract:
Pseudomonas aeruginosa est un pathogène opportuniste très résistant, pour lequel il est critique de trouver de nouvelles thérapies. Cette bactérie s’adapte facilement à son environnement grâce à son grand génome et à sa grande proportion de régulateurs permettant une régulation très fine de ses gènes. L’enveloppe est la première barrière au contact direct de l’environnement, et est un lieu d’échanges très important entre ce dernier et la bactérie. L’enveloppe représente donc une cible thérapeutique potentielle intéressante. SigX est un facteur sigma à fonction extracytoplasmique, permettant de répondre à des situations de stress d’enveloppe détectées par la bactérie, mais dont le stimulus exact reste à déterminer. Ce facteur sigma pourrait faire partie d’un nouveau système de transduction atypique du signal, qui pourrait coupler SigX à un canal mécanosensible. Ces travaux ont mené à la découverte de trois nouvelles conditions activatrices de SigX, l’infection par des phages Pf4, la perte du canal mécanosensible CmpX, et le choc froid. Ces dernières semblent provoquer de fortes perturbations et une augmentation de la rigidité membranaire qui pourrait être le stimulus activateur de SigX. Ces travaux ont permis d’étoffer les connaissances et de se rapprocher de la condition activatrice de SigX, et de préciser les fonctions cellulaires et régulatrices des membres du système SigX-CfrX-CmpX, mettant en exergue l’implication d’un canal mécanosensible dans la physiologie de Pseudomonas aeruginosaPseudomonas aeruginosa is a very resistant opportunistic pathogen, for which it is critical to find new therapies. This bacterium easily adapts to its environment, through its large genome and proportion of regulators allowing a very fine regulation of its genes. The cell wall is the first barrier in contact with environment, and therefore represents a very important place ofexchange. The cell wall thus represents an interesting potential therapeutic target. SigX is an extracytoplasmic function sigma factor, responding to cell wall stresses detected by the bacterium, but the precise stimulus remains to discover. This sigma factor could be part of a new atypical signal transduction system that could couple SigX with a mechanosensitive channel. This work has led to the discovery of three new sigX activating conditions, which are Pf4 phage infection, loss of the CmpX mechanosensitive channel, and cold shock. These conditions seem to cause strong perturbations and an increase in membrane stiffness that could be the activating stimulus of SigX. This work has led to a better understanding of the activating condition of SigX, and to the clarification of the cellular and regulatory functions of the SigXCfrX-CmpX system members, highlighting the involvement of a mechanosensitive channel in the physiology of Pseudomonas aeruginosa
9
Lacroix, Jean-Marie Bohin Jean-Pierre. "Les glucanes périplasmiques osmorégulés (OPG) chez les entérobactéries de la régulation osmotique à la virulence /." Villeneuve d'Ascq : Université des sciences et technologies de Lille, 2007. https://iris.univ-lille1.fr/dspace/handle/1908/1000.
Full textAbstract:
Reproduction de : Habilitation à diriger des recherches : Sciences naturelles. Biologie : Lille 1 : 2006.N° d'ordre (Lille 1) : 510. Titre provenant de la page de titre du document numérisé. Bibliogr. p. 41-56.
10
Zhang, Honghao. "Modulation of virulence of Streptococcus pneumoniae by an operon in conjugative transposon Tn5252." 2006. http://digital.library.okstate.edu/etd/umi-okstate-2057.pdf.
Full textBook chapters on the topic "Virulence Operon"
1
Cai, Hongyan, Jiaying Yu, Qiu Li, Youyu Zhang, and Lixing Huang. "Research Progress on Virulence Factors of Vibrio alginolyticus: A Key Pathogenic Bacteria of Sepsis." In Sepsis - New Perspectives [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.108206.
Full textAbstract:
As an opportunistic pathogen, V. alginolyticus is commonly found in people with weak immune systems or open wounds. The history of seafood exposure is a major feature of V. alginolyticus infection. V. alginolyticus can infect marine economic animals such as fish, shrimp, and shellfish, and is also one of the key pathogens that cause sepsis in human. Because of its rapid progress and extremely high mortality after the infection, it has received more and more attention in clinical practice. At present, there is no effective method to completely control the incidence of V. alginolyticus. Therefore, it is particularly important to study the virulence factors and pathogenic mechanisms of V. alginolyticus. This article reviews recent studies on virulence factors of V. alginolyticus, such as quorum sensing, virulence proteins, ferroportin hemolysin, flagella, lipopolysaccharide system and biofilm formation, with the hope of providing further insights into aquaculture and public health.
2
"Infection." In Standards for the Management of Open Fractures, edited by Simon Eccles, Bob Handley, Umraz Khan, Iain McFadyen, Jagdeep Nanchahal, and Selvadurai Nayagam, 125–34. Oxford University Press, 2020. http://dx.doi.org/10.1093/med/9780198849360.003.0013.
Full textAbstract:
Infection is the most feared and challenging complication in the treatment of open tibial fractures. Microorganisms can adhere as a biofilm on the surface of damaged bone, necrotic tissue, and internal fixation devices, and become resistant to phagocytosis and most antimicrobial agents. Established infection can delay healing and recovery, cause permanent functional loss, and potentially lead to amputation of the affected limb. The incidence of infection after severe open tibial fractures was reported to be over 30% in the 1980s and 1990s. Although there is evidence of a possible reduction in incidence in the past decade, the Lower Extremity Assessment Project (LEAP) study has shown that severe lower extremity trauma continues to be associated with infective complications necessitating additional operative treatment in a significant number of cases. Furthermore, greater bacterial virulence and increasing age and associated co-morbidities of the fracture population ensure that infection after open trauma remains a challenge.
3
Pruitt, Nicholas T. "Introduction." In Open Hearts, Closed Doors, 1–22. NYU Press, 2021. http://dx.doi.org/10.18574/nyu/9781479803545.003.0001.
Full textAbstract:
The introduction identifies the thesis that mainline Protestants by midcentury favored limited forms of pluralism and in turn fostered a more liberal immigration policy, while still hoping to Christianize the nation. This introduction outlines the structure of the book, while also drawing attention to the study’s application to histories of denominational institutions and home missions, politics and nativism, race, and gender. As they witnessed increasing diversity, mainline Protestants worked to shed the vestiges of virulent nativism from the prior century. Mainline Protestants worked to promote cosmopolitanism and eventually a moderate form of cultural pluralism, rather than embracing religious pluralism. But in so doing, they helped foster, inadvertently, both cultural and religious pluralism. In the end, this pluralistic bargain proved untenable and helped bring to an end more than three centuries of white Protestant hegemony in American society.
4
Chinnici, Joseph P. "Diversities, Silence, and Open Conflict." In American Catholicism Transformed, 53–83. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780197573006.003.0003.
Full textAbstract:
From 1940 to 1962, political and theological debates indicate that contemporary disagreements in the Church predate the Council. The geopolitical polices of the papacy influence various phases of development: (1) During the War, the clerical elite conduct a debate over Catholic cooperation in non-Catholic life. (2) From 1948 to 1955, international “containment” policies parallel the numerous allegations of heresy touching the views of Father Leonard Feeney, the social argument of Father James Keller, and the asceticism of Father John Hugo. John Courtney Murray’s studies on the American political proposition are silenced. (3) These largely private disagreements between “Right” and “Left” elements in the Church—represented by National Review, Fides Publishing, and others—experience a “cultural opening” and move into the public forum as the struggle against communism begins to lose its resonance. (4) Six months before the Council, political and theological disagreements express themselves in open and virulent juxtaposition.
5
Corredor, Mauricio, Juan David Patiño-Salazar, Diana Carolina Castaño, and Amalia Muñoz-Gómez. "The Pangenome of Pseudomonas aeruginosa." In Pseudomonas aeruginosa - New Perspectives and Applications [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.108187.
Full textAbstract:
This review summarizes the most important reports about Pseudomonas aeruginosa pangenome. Pan-genomics has tackled some fundamental concerns in pathogenic bacteria. PATRIC and other databases, store more than 9000 P. aeruginosa genomes. This data mining is an opportunity to develop discoveries related to antibiotic resistance, virulence, pathogenicity, fitness, and evolution, among others. Observing the different pangenomes of P. aeruginosa, it is concluded that this species has an open pangenome, and its accessory genome is larger than the central genome. HGT is one important source for P. aeruginosa genome. In recent years various authors developed P. aeruginosa pangenomes, from works with five genomes to more than 1300 genomes. This last work analyzed 54,272 genes, and they found a short and tiny core genome (only 665 genes). Other research with lesser strains or genomes identified a core genome bigger, almost 20% of the pangenome. Nevertheless, the total work proves that the accessory plus unique genome is larger than the core genome in P. aeruginosa.
Reports on the topic "Virulence Operon"
1
Elbaum, Michael, and Peter J. Christie. Type IV Secretion System of Agrobacterium tumefaciens: Components and Structures. United States Department of Agriculture, March 2013. http://dx.doi.org/10.32747/2013.7699848.bard.
Full textAbstract:
Objectives: The overall goal of the project was to build an ultrastructural model of the Agrobacterium tumefaciens type IV secretion system (T4SS) based on electron microscopy, genetics, and immunolocalization of its components. There were four original aims: Aim 1: Define the contributions of contact-dependent and -independent plant signals to formation of novel morphological changes at the A. tumefaciens polar membrane. Aim 2: Genetic basis for morphological changes at the A. tumefaciens polar membrane. Aim 3: Immuno-localization of VirB proteins Aim 4: Structural definition of the substrate translocation route. There were no major revisions to the aims, and the work focused on the above questions. Background: Agrobacterium presents a unique example of inter-kingdom gene transfer. The process involves cell to cell transfer of both protein and DNA substrates via a contact-dependent mechanism akin to bacterial conjugation. Transfer is mediated by a T4SS. Intensive study of the Agrobacterium T4SS has made it an archetypal model for the genetics and biochemistry. The channel is assembled from eleven protein components encoded on the B operon in the virulence region of the tumor-inducing plasmid, plus an additional coupling protein, VirD4. During the course of our project two structural studies were published presenting X-ray crystallography and three-dimensional reconstruction from electron microscopy of a core complex of the channel assembled in vitro from homologous proteins of E. coli, representing VirB7, VirB9, and VirB10. Another study was published claiming that the secretion channels in Agrobacterium appear on helical arrays around the membrane perimeter and along the entire length of the bacterium. Helical arrangements in bacterial membranes have since fallen from favor however, and that finding was partially retracted in a second publication. Overall, the localization of the T4SS within the bacterial membranes remains enigmatic in the literature, and we believe that our results from this project make a significant advance. Summary of achievements : We found that polar inflations and other membrane disturbances relate to the activation conditions rather than to virulence protein expression. Activation requires low pH and nutrient-poor medium. These stress conditions are also reflected in DNA condensation to varying degrees. Nonetheless, they must be considered in modeling the T4SS as they represent the relevant conditions for its expression and activity. We identified the T4SS core component VirB7 at native expression levels using state of the art super-resolution light microscopy. This marker of the secretion system was found almost exclusively at the cell poles, and typically one pole. Immuno-electron microscopy identified the protein at the inner membrane, rather than at bridges across the inner and outer membranes. This suggests a rare or transient assembly of the secretion-competent channel, or alternatively a two-step secretion involving an intermediate step in the periplasmic space. We followed the expression of the major secreted effector, VirE2. This is a single-stranded DNA binding protein that forms a capsid around the transferred oligonucleotide, adapting the bacterial conjugation to the eukaryotic host. We found that over-expressed VirE2 forms filamentous complexes in the bacterial cytoplasm that could be observed both by conventional fluorescence microscopy and by correlative electron cryo-tomography. Using a non-retentive mutant we observed secretion of VirE2 from bacterial poles. We labeled the secreted substrates in vivo in order detect their secretion and appearance in the plant cells. However the low transfer efficiency and significant background signal have so far hampered this approach.
2
Kapulnik, Yoram, and Donald A. Phillips. Isoflavonoid Regulation of Root Bacteria. United States Department of Agriculture, January 1996. http://dx.doi.org/10.32747/1996.7570561.bard.
Full textAbstract:
The overall objective of this project was to develop a conceptual framework for enhancing root colonization by beneficial bacteria. To accomplish this aim we tested the hypothesis that production and excretion of the plant phytoalexin medicarpin can be used for creation of a special niche along the legume roots, where beneficial microorganism, such as rhizobium, will have a selective advantage. On the Israeli side it was shown that higher medicarpin levels are exuded following the application of Rhizobium meliloti to the rhizosphere but the specific biochemical pathway governing medicarpin production was not induced significantly enough to support a constant production and excretion of this molecule to the rhizosphere. Furthermore, pathogenic bacteria and chemical elicitors were found to induce higher levels of this phytoalexin and it became important to test its natural abundance in field grown plants. On the US side, the occurrence of flavonoids and nucleosides in agricultural soils has been evaluated and biologically significant quantities of these molecules were identified. A more virulent Agrobacterium tumefaciens strain was isolated from alfalfa (Medicago sativa L.) which forms tumors on a wide range of plant species. This isolate contains genes that increase competitive colonization abilities on roots by reducing the accumulation of alfalfa isoflavonoids in the bacterial cells. Following gene tagging efforts the US lab found that mutation in the bacterial efflux pump operons of this isolate reduced its competitive abilities. This results support our original hypothesis that detoxification activity of isoflavenoids molecules, based on bacterial gene(s), is an important selection mechanism in the rhizosphere. In addition, we focused on biotin as a regulatory element in the rhizosphere to support growth of some rhizosphere microorganisms and designed a bacterial gene construct carrying the biotin-binding protein, streptavidin. Expressing this gene in tobacco roots did not affect the biotin level but its expression in alfalfa was lethal. In conclusion, the collaborative combination of basic and applied approaches toward the understanding of rhizosphere activity yielded new knowledge related to the colonization of roots by beneficial microorganisms in the presence of biological active molecules exuded from the plant roots.
3
Lindow, Steven E., Shulamit Manulis, Dan Zutra, and Dan Gaash. Evaluation of Strategies and Implementation of Biological Control of Fire Blight. United States Department of Agriculture, July 1993. http://dx.doi.org/10.32747/1993.7568106.bard.
Full textAbstract:
The main objective of this study was to develop data that would facilitate a consistently effective method of biological control of fire blight disease to be developed and to enable its implementation for disease control by ensuring its compatibility with variations in the biological, environmental, and chemical conditions present in pear orchards. As considerable information on the pathogen and biological control of fire blight was already gathered from studies in California and elsewhere, an emphasis was placed on investigating the genetics and ecology of Erwinia amylovora, the causal agent of fire blight in Israel. Studies of plasmid profile, virulence on several host, serological characteristics, as well as DNA fingerprints with selected primers all revealed E. amylovora strains in Israel to be homogeneous. Strains did vary in their resistance to streptomycin, with those from more northern locations being resistant while those in the southern costal plain were all sensitive to streptomycin. Resistance appeared to be conferred by chromosomal mutations as in streptomycin-resistant strains in California. The biological control agent Pseudomonas fluorescens strain A506 colonized flowers of both the Costia and Spodona pear cultivars in Israel as well as Bartlett pear in California. Flowers that were open at the time of spray inoculation of trees subsequently harbored from 105 to 107 cells of strain A506 per flower, while those that opened subsequent to spraying developed population sizes of about 105 cells/flower within 5 days. The incidence of fire blight infections were reduced about 3-fold in several trials in which moderate amounts of disease occurred in the plot areas; this degree of biological control is similar to that observed in California and elsewhere. On two occasions warm and moist weather that favored disease led to epidemics in which nearly all flowers became infected and which was so severe that neither P. fluorescens strain A506 nor chemical bactericides reduced disease incidence. A novel method for identifying antagonistic microorganisms for biological control of fire blight and other diseases was developed. A bacterial ice nucleation gene was introduced into E. amylovora to confer an Ice+ phenotype and the population sizes of this modified pathogen on flowers that had been pre-treated with potential control agents was estimated by measuring the freezing temperature of colonized flowers. Antagonistic strains that prevented the growth of E. amylovora in flowers were readily detected as those in which flowers froze at a low temperature. The method is both rapid and unbiased and several bacterial strains with substantial biological control potential have been identified using this method.
4
McElwain, Terry F., Eugene Pipano, Guy H. Palmer, Varda Shkap, Stephn A. Hines, and Wendy C. Brown. Protection of Cattle against Babesiosis: Immunization against Babesia bovis with an Optimized RAP-1/Apical Complex Construct. United States Department of Agriculture, September 1999. http://dx.doi.org/10.32747/1999.7573063.bard.
Full textAbstract:
Previous research and current efforts at control of babesiosis fall short of meeting the needs of countries where the disease is endemic, such as Israel, as well as the needs of exporting countries and countries bordering on endemic areas, such as the U.S. Our long-term goal is to develop improved methods of immunization against bovine babesiosis based on an understanding of the molecular mechanisms of immune protection and parasite targets of a protective immune response. In our previous BARD project, we established the basis for focusing on rhoptry antigens as components of a subunit vaccine against bovine babesiosis, and for additional research to better characterize rhoptry associated protein-1 (RAP-1) as a target of protective immunity. In this continuation BARD project, our objectives were to [1] optimize the immune response against RAP-1, and [2] identify additional rhoptry candidate vaccine antigens. The entire locus encoding B. bovis RAP-1 was sequenced, and the rap-1 open reading frame compared among several strains. Unlike B. bigemina, in which multiple gene copies with variant domains encode RAP-1, the B. bovis RAP-1 locus contains only two identical genes which are conserved among strains. Through testing of multiple truncated constructs of rRAP-1, one or more immunodominant T cell epitopes were mapped to the amino terminal half of RAP-1. At least one linear and one conformational B cell epitope have been demonstrated in the same amino terminal construct, which in B. bigemina RAP-1 also contains an epitope recognized by neutralizing antibody. The amine terminal half of the molecule represents the most highly conserved part of the gene family and contains motifs conserved broadly among the apicomplexa. In contrast, the carboxy terminal half of B. bovis RAP-1 is less well conserved and contains multiple repeats encoding a linear B cell epitope potentially capable of inducing an ineffective, T cell independent, type 2 immune response. Therefore, we are testing an amino terminal fragment of RAP-1 (RAP-1N) in an immunization trial in cattle. Cattle have beer immunized with RAP-1N or control antigen, and IL-12 with Ribi adjuvant. Evaluation of the immune response is ongoing, and challenge with virulent B. bovis will occur in the near future. While no new rhoptry antigens were identified, our studies did identify and characterize a new spherical body antigen (SBP3), and several heat shock proteins (HSP's). The SBP3 and HSP21 antigens stimulate T cells from immune cattle and are considered new vaccine candidates worthy of further testing. Overall, we conclude that a single RAP-1 vaccine construct representing the conserved amino terminal region of the molecule should be sufficient for immunization against all strains of B. bovis. While results of the ongoing immunization trial will direct our next research steps, results at this time are consistent with our long term goal of designing a subunit vaccine which contains only the epitopes relevant to induction of protective immunity. Parallel studies are defining the mechanisms of protective immunity. Apicomplexan protozoa, including babesiosis and malaria, cause persistent diseases for which control is inadequate. The apical organelles are defining features of these complex protozoa, and have been conserved through the evolutionary process, Past and current BARD projects on babesiosis have established the validity and potential of exploiting these conserved organelles in developing improved control methods applicable to all apicomplexan diseases.