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Kitten, Todd, Cindy L. Munro, Suzanne M. Michalek i Francis L. Macrina. "Genetic Characterization of a Streptococcus mutans LraI Family Operon and Role in Virulence". Infection and Immunity 68, nr 8 (1.08.2000): 4441–51. http://dx.doi.org/10.1128/iai.68.8.4441-4451.2000.
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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.
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Salvail, Hubert, Jeongjoon Choi i Eduardo A. Groisman. "Differential synthesis of novel small protein times Salmonella virulence program". PLOS Genetics 18, nr 3 (4.03.2022): e1010074. http://dx.doi.org/10.1371/journal.pgen.1010074.
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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.
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Day, William A., i Anthony T. Maurelli. "Shigella flexneri LuxS Quorum-Sensing System Modulates virB Expression but Is Not Essential for Virulence". Infection and Immunity 69, nr 1 (1.01.2001): 15–23. http://dx.doi.org/10.1128/iai.69.1.15-23.2001.
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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.
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Miranda-CasoLuengo, Raúl, Aleksandra A. Miranda-CasoLuengo, Enda P. O’Connell, Ruth J. Fahey, Clara A. Boland, Jose A. Vázquez-Boland i Wim G. Meijer. "The vapA co-expressed virulence plasmid gene vcgB (orf10) of the intracellular actinomycete Rhodococcus equi". Microbiology 157, nr 8 (1.08.2011): 2357–68. http://dx.doi.org/10.1099/mic.0.049759-0.
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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.
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Tobe, Toru, Tetsuya Hayashi, Chang-Gyun Han, Gary K. Schoolnik, Eiichi Ohtsubo i Chihiro Sasakawa. "Complete DNA Sequence and Structural Analysis of the Enteropathogenic Escherichia coli Adherence Factor Plasmid". Infection and Immunity 67, nr 10 (1.10.1999): 5455–62. http://dx.doi.org/10.1128/iai.67.10.5455-5462.1999.
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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.
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Mole, Beth, Sohrab Habibi, Jeffery L. Dangl i Sarah R. Grant. "Gluconate Metabolism Is Required for Virulence of the Soft-Rot Pathogen Pectobacterium carotovorum". Molecular Plant-Microbe Interactions® 23, nr 10 (październik 2010): 1335–44. http://dx.doi.org/10.1094/mpmi-03-10-0067.
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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.
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Vu-Khac, Hung, i 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, nr 21 (4.09.2009): 6671–78. http://dx.doi.org/10.1128/aem.01104-09.
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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.
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Onasanya, Amos, R. O. Onasanya, Abiodun A. Ojo i B. O. Adewale. "Genetic Analysis and Molecular Identification of Virulence in Xanthomonas oryzae pv. oryzae Isolates". ISRN Molecular Biology 2013 (8.09.2013): 1–8. http://dx.doi.org/10.1155/2013/160157.
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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.
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Wright, Anita C., Jan L. Powell, James B. Kaper i J. Glenn Morris. "Identification of a Group 1-Like Capsular Polysaccharide Operon for Vibrio vulnificus". Infection and Immunity 69, nr 11 (1.11.2001): 6893–901. http://dx.doi.org/10.1128/iai.69.11.6893-6901.2001.
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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.
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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 i Bo Li. "Phevamine A, a small molecule that suppresses plant immune responses". Proceedings of the National Academy of Sciences 115, nr 41 (20.09.2018): E9514—E9522. http://dx.doi.org/10.1073/pnas.1803779115.
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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.
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Lowe, Beth A., Jesse D. Miller i Melody N. Neely. "Analysis of the Polysaccharide Capsule of the Systemic Pathogen Streptococcus iniae and Its Implications in Virulence". Infection and Immunity 75, nr 3 (28.12.2006): 1255–64. http://dx.doi.org/10.1128/iai.01484-06.
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ABSTRACT Systemic pathogens have developed numerous strategies for evading the defenses of the host, permitting dissemination and multiplication in various tissues. One means of survival in the host, particularly in the bloodstream, has been attributed to the ability to avoid phagocytosis via capsular polysaccharide. To further define the virulence capacity of Streptococcus iniae, a zoonotic pathogen with the ability to cause severe systemic disease in both fish and humans, we performed an analysis of the capsule locus. The initial analysis included cloning and sequencing of the capsule synthesis operon, which revealed an approximately 21-kb region that is highly homologous to capsule operons of other streptococci. A genetic comparison of S. iniae virulent strain 9117 and commensal strain 9066 revealed that the commensal strain does not have the central region of the capsule operon composed of several important capsule synthesis genes. Four 9117 insertion or deletion mutants with mutations in the beginning, middle, or end of the capsule locus were analyzed to determine their capsule production and virulence. Virulence profiles were analyzed for each mutant using three separate criteria, which demonstrated the attenuation of each mutant in several tissue environments. These analyses also provided insight into the different responses of the host to each mutant strain compared to a wild-type infection. Our results demonstrate that capsule is not required for all host environments, while excess capsule is also not optimal, suggesting that for an “ideal” systemic infection, capsule production is most likely regulated while the bacterium is in different environments of the host.
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Dapgh, A. N., A. S. Hakim, H. A. Abouelhag, A. M. Abdou i E. A. Elgabry. "Detection of virulence and multidrug resistance operons in Pseudomonas aeruginosa isolated from Egyptian Baladi sheep and goat". October-2019 12, nr 10 (październik 2019): 1524–28. http://dx.doi.org/10.14202/vetworld.2019.1524-1528.
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Background: Pseudomonas aeruginosa is a pit of an enormous group of free-living bacteria that are able to live everywhere and suggested to be the causative agent of great scope of acute and chronic animal infections. Aim: The current study was carried out to illustrate the prevalence of P. aeruginosa in small ruminants and existence of some virulence operons as well as its antimicrobial resistance. Materials and Methods: A total of 155 samples from sheep and 105 samples from goats (mouth abscesses, fecal swabs, nasal, tracheal swabs, and lung tissue) were collected for bacteriological study, existence of some virulence expression operons with the study of their sensitivity to the antimicrobials using disc diffusion and presence of mexR operon which is responsible for multidrug resistance (MDR). Results: The bacteriological examination revealed that P. aeruginosa was isolated from nine out of 155 samples from sheep (5.8%) and four isolates out of 105 samples from goat (3.8%). It is found that 12 (92.3%), 10 (76.9 %), and 8 (61.5%) of P. aeruginosa isolates harbored hemolysin phospholipase gene (pclH), gene (exoS), and enterotoxin gene (toxA), respectively. The results of antibiotic sensitivity test showed that all tested isolates were resistant to ampicillin, bacitracin, erythromycin, streptomycin, tetracycline, trimethoprim-sulfamethoxazole, and tobramycin but sensitive to ciprofloxacin and norfloxacin. The MDR (mexR) operon was existed in all isolates. Conclusion: There is a growing risk for isolation of virulent MDR P. aeruginosa from sheep and goat illness cases, and this should be regarded in the efficient control programs.
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Haneda, Takeshi, Nobuhiko Okada, Noriko Nakazawa, Takatoshi Kawakami i Hirofumi Danbara. "Complete DNA Sequence and Comparative Analysis of the 50-Kilobase Virulence Plasmid of Salmonella entericaSerovar Choleraesuis". Infection and Immunity 69, nr 4 (1.04.2001): 2612–20. http://dx.doi.org/10.1128/iai.69.4.2612-2620.2001.
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ABSTRACT The complete nucleotide sequence of pKDSC50, a large virulence plasmid from Salmonella enterica serovar Choleraesuis strain RF-1, has been determined. We identified 48 of the open reading frames (ORFs) encoded by the 49,503-bp molecule. pKDSC50 encodes a known virulence-associated operon, the spv operon, which is composed of genes essential for systemic infection by nontyphoidalSalmonella. Analysis of the genetic organization of pKDSC50 suggests that the plasmid is composed of several virulence-associated genes, which include the spvRABCD genes, plasmid replication and maintenance genes, and one insertion sequence element. A second virulence-associated region including the pef(plasmid-encoded fimbria) operon and rck (resistance to complement killing) gene, which has been identified on the virulence plasmid of S. enterica serovar Typhimurium, was absent. Two different replicon regions, similar to the RepFIIA and RepFIB replicons, were found. Both showed high similarity to those of the pO157 plasmid of enterohemorrhagic Escherichia coliO157:H7 and the enteropathogenic E. coli (EPEC) adherence factor plasmid harbored by EPEC strain B171 (O111:NM), as well as the virulence plasmids of Salmonella serovars Typhimurium and Enteritidis. Comparative analysis of the nucleotide sequences of the 50-kb virulence plasmid of serovar Choleraesuis and the 94-kb virulence plasmid of serovar Typhimurium revealed that 47 out of 48 ORFs of the virulence plasmid of serovar Choleraesuis are highly homologous to the corresponding ORFs of the virulence plasmid of serovar Typhimurium, suggesting a common ancestry.
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Tivendale, Kelly A., Joanne L. Allen, Carol A. Ginns, Brendan S. Crabb i Glenn F. Browning. "Association of iss and iucA, but Not tsh, with Plasmid-Mediated Virulence of Avian Pathogenic Escherichia coli". Infection and Immunity 72, nr 11 (listopad 2004): 6554–60. http://dx.doi.org/10.1128/iai.72.11.6554-6560.2004.
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ABSTRACT Avian pathogenic Escherichia coli (APEC) is an economically important respiratory pathogen of chickens worldwide. Factors previously associated with the virulence of APEC include adhesins, iron-scavenging mechanisms, the production of colicin V (ColV), serum resistance, and temperature-sensitive hemagglutination, but virulence has generally been assessed by parenteral inoculation, which does not replicate the normal respiratory route of infection. A large plasmid, pVM01, is essential for virulence in APEC strain E3 in chickens after aerosol exposure. Here we establish the size of pVM01 to be approximately 160 kb and show that the putative virulence genes iss (increased serum survival) and tsh (temperature-sensitive hemagglutinin) and the aerobactin operon are on the plasmid. These genes were not clustered on pVM01 but, rather, were each located in quite distinct regions. Examination of APEC strains with defined levels of respiratory pathogenicity after aerosol exposure showed that both the aerobactin operon and iss were associated with high levels of virulence in APEC but that the possession of either gene was sufficient for intermediate levels of virulence. In constrast, the presence of tsh was not necessary for high levels of virulence. Thus, both the aerobactin operon and iss are associated with virulence in APEC after exposure by the natural route of infection. The similarities between APEC and extraintestinal E. coli infection in other species suggests that they may be useful models for definition of the role of these virulence genes and of other novel virulence genes that may be located on their virulence plasmids.
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Luong, Thanh T., i Chia Y. Lee. "Overproduction of Type 8 Capsular Polysaccharide Augments Staphylococcus aureus Virulence". Infection and Immunity 70, nr 7 (lipiec 2002): 3389–95. http://dx.doi.org/10.1128/iai.70.7.3389-3395.2002.
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ABSTRACT Type 8 capsular polysaccharide (CP8) is the most prevalent capsule type in clinical isolates of Staphylococcus aureus. However, its role in virulence has not been clearly defined. CP8 strains such as strain Becker produce a small amount of capsule on their surface in vitro. In contrast, CP1 strains such as strain M produce a large amount of capsule, which has been shown to be an important antiphagocytic virulence factor. The cap8 and cap1 operons, required for the synthesis of CP8 and CP1, respectively, have been cloned and sequenced. To test whether CP8 contributes to the pathogenesis of S. aureus, we replaced the weak native promoter of the cap8 operon in strain Becker with the strong constitutive promoter of the cap1 operon of strain M. The resultant strain, CYL770, synthesized cap8-specific mRNA at a level about sevenfold higher than that in the parent strain. Remarkably, the CYL770 strain produced about 80-fold more CP8. In a mouse infection model of bacteremia, the CP8-overproducing strain persisted longer in the bloodstream, the liver, and the spleen in mice than the parent strain. In addition, strain CYL770 was more resistant to ospsonophagocytosis in vitro by human polymorphonuclear leukocytes. These results indicate that CP8 is an antiphagocytic virulence factor of S. aureus.
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Johnson, Timothy J., Sara J. Johnson i Lisa K. Nolan. "Complete DNA Sequence of a ColBM Plasmid from Avian Pathogenic Escherichia coli Suggests that It Evolved from Closely Related ColV Virulence Plasmids". Journal of Bacteriology 188, nr 16 (15.08.2006): 5975–83. http://dx.doi.org/10.1128/jb.00204-06.
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ABSTRACT Avian pathogenic Escherichia coli (APEC), an extraintestinal pathogenic E. coli causing colibacillosis in birds, is responsible for significant economic losses for the poultry industry. Recently, we reported that the APEC pathotype was characterized by possession of a set of genes contained within a 94-kb cluster linked to a ColV plasmid, pAPEC-O2-ColV. These included sitABCD, genes of the aerobactin operon, hlyF, iss, genes of the salmochelin operon, and the 5′ end of cvaB of the ColV operon. However, the results of gene prevalence studies performed among APEC isolates revealed that these traits were not always linked to ColV plasmids. Here, we present the complete sequence of a 174-kb plasmid, pAPEC-O1-ColBM, which contains a putative virulence cluster similar to that of pAPEC-O2-ColV. These two F-type plasmids share remarkable similarity, except that they encode the production of different colicins; pAPEC-O2-ColV contains an intact ColV operon, and pAPEC-O1-ColBM encodes the colicins B and M. Interestingly, remnants of the ColV operon exist in pAPEC-O1-ColBM, hinting that ColBM-type plasmids may have evolved from ColV plasmids. Among APEC isolates, the prevalence of ColBM sequences helps account for the previously observed differences in prevalence between genes of the “conserved” portion of the putative virulence cluster of pAPEC-O2-ColV and those genes within its “variable” portion. These results, in conjunction with Southern blotting and probing of representative ColBM-positive strains, indicate that this “conserved” cluster of putative virulence genes is primarily linked to F-type virulence plasmids among the APEC isolates studied.
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Fouet, Agnès, Olivier Namy i Guillaume Lambert. "Characterization of the Operon Encoding the Alternative ςB Factor from Bacillus anthracis and Its Role in Virulence". Journal of Bacteriology 182, nr 18 (15.09.2000): 5036–45. http://dx.doi.org/10.1128/jb.182.18.5036-5045.2000.
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ABSTRACT The operon encoding the general stress transcription factor ςB and two proteins of its regulatory network, RsbV and RsbW, was cloned from the gram-positive bacterium Bacillus anthracis by PCR amplification of chromosomal DNA with degenerate primers, by inverse PCR, and by direct cloning. The gene cluster was very similar to the Bacillus subtilis sigB operon both in the primary sequences of the gene products and in the order of its three genes. However, the deduced products of sequences upstream and downstream from this operon showed no similarity to other proteins encoded by the B. subtilis sigB operon. Therefore, the B. anthracis sigB operon contains three genes rather than eight as in B. subtilis. TheB. anthracis operon is preceded by a ςB-like promoter sequence, the expression of which depends on an intact ςB transcription factor in B. subtilis. It is followed by another open reading frame that is also preceded by a promoter sequence similarly dependent on B. subtilis ςB. We found that in B. anthracis, both these promoters were induced during the stationary phase and induction required an intact sigBgene. The sigB operon was induced by heat shock. Mutants from which sigB was deleted were constructed in a toxinogenic and a plasmidless strain. These mutants differed from the parental strains in terms of morphology. The toxinogenicsigB mutant strain was also less virulent than the parental strain in the mouse model. B. anthracis ςBmay therefore be a minor virulence factor.
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Teplitski, Max, Ali Al-Agely i Brian M. M. Ahmer. "Contribution of the SirA regulon to biofilm formation in Salmonella enterica serovar Typhimurium". Microbiology 152, nr 11 (1.11.2006): 3411–24. http://dx.doi.org/10.1099/mic.0.29118-0.
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Orthologues of the Salmonella enterica serovar Typhimurium (S. typhimurium) BarA/SirA two-component system are important for biofilm formation and virulence in many γ-Proteobacteria. In S. typhimurium, SirA activates the csrB and csrC carbon storage regulatory RNAs and the virulence gene regulators hilA and hilC. The regulatory RNAs antagonize the activity of the CsrA protein, allowing translation of those same virulence genes, and inhibiting the translation of flagellar genes. In this report, it was determined that SirA and the Csr system also control the fim operon that encodes type 1 fimbriae. sirA orthologues in other bacterial species, and the fim operon of S. typhimurium, are known to play a role in biofilm formation; therefore, all members of the S. typhimurium sirA regulon were tested for in vitro biofilm production. A sirA mutant, a csrB csrC double mutant, and a fimI mutant, were all defective in biofilm formation. Conversely, inactivation of flhDC increased biofilm formation. Therefore, SirA activates csrB, csrC and the fim operon to promote biofilm formation. In turn, csrB and csrC promote the translation of the fim operon, while at the same time inhibiting the translation of flagella, which are inhibitory to biofilm formation.
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Hefty, P. Scott, i Richard S. Stephens. "Chlamydial Type III Secretion System Is Encoded on Ten Operons Preceded by Sigma 70-Like Promoter Elements". Journal of Bacteriology 189, nr 1 (20.10.2006): 198–206. http://dx.doi.org/10.1128/jb.01034-06.
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ABSTRACT Many gram-negative bacterial pathogens employ type III secretion systems for infectious processes. Chlamydiae are obligate intracellular bacteria that encode a conserved type III secretion system that is likely requisite for growth. Typically, genes encoding type III secretion systems are located in a single locus; however, for chlamydiae these genes are scattered throughout the genome. Little is known regarding the gene regulatory mechanisms for this essential virulence determinant. To facilitate identification of cis-acting transcriptional regulatory elements, the operon structure was determined. This analysis revealed 10 operons that contained 37 genes associated with the type III secretion system. Linkage within these operons suggests a role in type III secretion for each of these genes, including 13 genes encoding proteins with unknown function. The transcriptional start site for each operon was determined. In conjunction with promoter activity assays, this analysis revealed that the type III secretion system operons encode σ70-like promoter elements. Transcriptional initiation by a sigma factor responsible for constitutive gene expression indicates that undefined activators or repressors regulate developmental stage-specific expression of chlamydial type III secretion system genes.
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Tauschek, Marija, Ji Yang, Dianna Hocking, Kristy Azzopardi, Aimee Tan, Emily Hart, Judyta Praszkier i Roy M. Robins-Browne. "Transcriptional Analysis of the grlRA Virulence Operon from Citrobacter rodentium". Journal of Bacteriology 192, nr 14 (14.05.2010): 3722–34. http://dx.doi.org/10.1128/jb.01540-09.
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ABSTRACT The locus for enterocyte effacement (LEE) is the virulence hallmark of the attaching-and-effacing (A/E) intestinal pathogens, namely, enteropathogenic Escherichia coli, enterohemorrhagic E. coli, and Citrobacter rodentium. The LEE carries more than 40 genes that are arranged in several operons, e.g., LEE1 to LEE5. Expression of the various transcriptional units is subject to xenogeneic silencing by the histone-like protein H-NS. The LEE1-encoded regulator, Ler, plays a key role in relieving this repression at several major LEE promoters, including LEE2 to LEE5. To achieve appropriate intracellular concentrations of Ler in different environments, A/E pathogens have evolved a sophisticated regulatory network to control ler expression. For example, the LEE-encoded GrlA and GrlR proteins work as activator and antiactivator, respectively, of ler transcription. Thus, control of the transcriptional activities of the LEE1 (ler) promoter and the grlRA operon determines the rate of transcription of all of the LEE-encoded virulence factors. To date, only a single promoter has been identified for the grlRA operon. In this study, we showed that the non-LEE-encoded AraC-like regulatory protein RegA of C. rodentium directly stimulates transcription of the grlRA promoter by binding to an upstream region in the presence of bicarbonate ions. In addition, in vivo and in vitro transcription assays revealed a σ70 promoter that is specifically responsible for transcription of grlA. Expression from this promoter was strongly repressed by H-NS and its paralog StpA but was activated by Ler. DNase I footprinting demonstrated that Ler binds to a region upstream of the grlA promoter, whereas H-NS interacts specifically with a region extending from the grlA core promoter into its coding sequence. Together, these findings provide new insights into the environmental regulation and differential expressions of the grlR and grlA genes of C. rodentium.
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Condemine, Guy, Arnaud Castillo, Fabrice Passeri i Corine Enard. "The PecT Repressor Coregulates Synthesis of Exopolysaccharides and Virulence Factors in Erwinia chrysanthemi". Molecular Plant-Microbe Interactions® 12, nr 1 (styczeń 1999): 45–52. http://dx.doi.org/10.1094/mpmi.1999.12.1.45.
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Erwinia chrysanthemi 3937 synthesizes an exopolysaccharide (EPS) composed of rhamnose, galactose, and galacturonic acid. Fourteen transcriptional fusions in genes required for EPS synthesis, named eps, were obtained by Tn5-B21 mutagenesis. Eleven of them are clustered on the chromosome and are repressed by PecT, a regulator of pectate lyase synthesis. In addition, expression of these fusions is repressed by the catabolite regulatory protein, CRP, and induced in low osmolarity medium. The three other mutations are located in genes that are not regulated by pecT. A 13-kb DNA fragment containing pecT-regulated eps genes has been cloned. All the genes identified on this fragment are transcribed in the same orientation and could form a large operon. The promoter region of this operon has been sequenced. It contains a JUMP-start sequence, a sequence required for the expression of polysaccharide-associated operons. E. chrysanthemi 3937 produces a systemic soft rot on its host Saintpaulia ionantha. An eps mutant was less efficient than the wild-type strain in initiating a maceration symptom, suggesting that production of EPS is required for the full expression of the E. chrysanthemi virulence.
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Yang, Xiaowen, Jiawei Wang, Ziyan Feng, Xiangjian Zhang, Xiangguo Wang i Qingmin Wu. "Relation of the pdxB-usg-truA-dedA Operon and the truA Gene to the Intracellular Survival of Salmonella enterica Serovar Typhimurium". International Journal of Molecular Sciences 20, nr 2 (17.01.2019): 380. http://dx.doi.org/10.3390/ijms20020380.
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Salmonella is the genus of Gram-negative, facultative intracellular pathogens that have the ability to infect large numbers of animal or human hosts. The S. enterica usg gene is associated with intracellular survival based on ortholog screening and identification. In this study, the λ-Red recombination system was used to construct gene deletion strains and to investigate whether the identified operon was related to intracellular survival. The pdxB-usg-truA-dedA operon enhanced the intracellular survival of S. enterica by resisting the oxidative environment and the usg and truA gene expression was induced by H2O2. Moreover, the genes in this operon (except for dedA) contributed to virulence in mice. These findings indicate that the pdxB-usg-truA-dedA operon functions in resistance to oxidative environments during intracellular survival and is required for in vivo S. enterica virulence. This study provides insight toward a better understand of the characteristics of intracellular pathogens and explores the gene modules involved in their intracellular survival.
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Haack, Kenneth R., Christopher L. Robinson, Kristie J. Miller, Jonathan W. Fowlkes i Jay L. Mellies. "Interaction of Ler at the LEE5 (tir) Operon of Enteropathogenic Escherichia coli". Infection and Immunity 71, nr 1 (styczeń 2003): 384–92. http://dx.doi.org/10.1128/iai.71.1.384-392.2003.
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ABSTRACT The genome of enteropathogenic Escherichia coli (EPEC) encodes a global regulator, Ler (locus of enterocyte effacement [LEE]-encoded regulator), which activates expression of several polycistronic operons within the 35.6-kb LEE pathogenicity island, including the LEE2-LEE3 divergent operon pair containing overlapping −10 regions and the LEE5 (tir) operon. Ler is a predicted 15-kDa protein that exhibits amino acid similarity with the nucleoid protein H-NS. In order to study Ler-mediated activation of virulence operons in EPEC, we used a molecular approach to characterize the interactions of purified Ler protein with the upstream regulatory sequences of the LEE5 operon. We determined the cis-acting DNA sequences necessary for Ler binding at LEE5 by mobility shift and DNase I protection assays, demonstrating that Ler acts directly at LEE5 by binding sequences between positions −190 and −73 in relation to the transcriptional start site. Based on the molecular weight of Ler, the similarity to H-NS, and the extended region of protection observed in a DNase I footprint at LEE5, we hypothesized that multiple Ler proteins bind upstream of the LEE5 promoter to increase transcriptional activity from a distance. Using an hns deletion strain, we demonstrated that like the LEE2-LEE3 operon pair, H-NS represses LEE5 transcription. We describe a model in which Ler activates transcription at both divergent overlapping paired and single promoters by displacing H-NS, which results in the disruption of a repressing nucleoprotein complex.
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Li, Michelle, Kyle Wang, Ashley Tang, Aaron Tang, Andrew Chen i Zuyi Huang. "Investigation of the Genes Involved in the Outbreaks of Escherichia coli and Salmonella spp. in the United States". Antibiotics 10, nr 10 (19.10.2021): 1274. http://dx.doi.org/10.3390/antibiotics10101274.
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Salmonella spp. and Escherichiacoli (E. coli) are two of the deadliest foodborne pathogens in the US. Genes involved in antimicrobial resistance, virulence, and stress response, enable these pathogens to increase their pathogenicity. This study aims to examine the genes detected in both outbreak and non-outbreak Salmonella spp. and E. coli by analyzing the data from the National Centre for Biotechnology Information (NCBI) Pathogen Detection Isolates Browser database. A multivariate statistical analysis was conducted on the genes detected in isolates of outbreak Salmonella spp., non-outbreak Salmonella spp., outbreak E. coli, and non-outbreak E. coli. The genes from the data were projected onto a two-dimensional space through principal component analysis. Hierarchical clustering was then used to quantify the relationship between the genes in the dataset. Most of the outlier genes identified in E. coli isolates are virulence genes, while outlier genes identified in Salmonella spp. are mainly involved in stress response. Gene epeA, which encodes a high-molecular-weight serine protease autotransporter of Enterobacteriaceae (SPATE) protein, along with subA and subB that encode cytotoxic activity, may contribute to the pathogenesis of outbreak E. coli. The iro operon and ars operon may play a role in the ecological success of the epidemic clones of Salmonella spp. Concurrent relationships between esp and ter operons in E. coli and pco and sil operons in Salmonella spp. are found. Stress-response genes (asr, golT, golS), virulence gene (sinH), and antimicrobial resistance genes (mdsA and mdsB) in Salmonella spp. also show a concurrent relationship. All these findings provide helpful information for experiment design to combat outbreaks of E. coli and Salmonella spp.
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Liu, Moqing, Alejandro F. Alice, Hiroaki Naka i Jorge H. Crosa. "The HlyU Protein Is a Positive Regulator of rtxA1, a Gene Responsible for Cytotoxicity and Virulence in the Human Pathogen Vibrio vulnificus". Infection and Immunity 75, nr 7 (16.04.2007): 3282–89. http://dx.doi.org/10.1128/iai.00045-07.
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ABSTRACT Vibrio vulnificus is an opportunistic human pathogen that preferentially infects compromised iron-overloaded patients, causing a fatal primary septicemia with very rapid progress, resulting in a high mortality rate. In this study we determined that the HlyU protein, a virulence factor in V. vulnificus CMCP6, up-regulates the expression of VV20479, a homologue of the Vibrio cholerae RTX (repeats in toxin) toxin gene that we named rtxA1. This gene is part of an operon together with two other open reading frames, VV20481 and VV20480, that encode two predicted proteins, a peptide chain release factor 1 and a hemolysin acyltransferase, respectively. A mutation in rtxA1 not only contributes to the loss of cytotoxic activity but also results in a decrease in virulence, whereas a deletion of VV20481 and VV20480 causes a slight decrease in virulence but with no effect in cytotoxicity. Activation of the expression of the rtxA1 operon by HlyU occurs at the transcription initiation level by binding of the HlyU protein to a region upstream of this operon.
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Kentache, Takfarinas, Eliane Milohanic, Thanh Nguyen Cao, Abdelhamid Mokhtari, Francine Moussan Aké, Que Mai Ma Pham, Philippe Joyet i Josef Deutscher. "Transport and Catabolism of Pentitols by Listeria monocytogenes". Journal of Molecular Microbiology and Biotechnology 26, nr 6 (2016): 369–80. http://dx.doi.org/10.1159/000447774.
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Transposon insertion into <i>Listeria monocytogenes lmo2665</i>, which encodes an EIIC of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS), was found to prevent <smlcap>D</smlcap>-arabitol utilization. We confirm this result with a deletion mutant and show that Lmo2665 is also required for <smlcap>D</smlcap>-xylitol utilization. We therefore called this protein EIIC<sup>Axl</sup>. Both pentitols are probably catabolized via the pentose phosphate pathway (PPP) because <i>lmo2665</i> belongs to an operon, which encodes the three PTS<sup>Axl</sup> components, two sugar-P dehydrogenases, and most PPP enzymes. The two dehydrogenases oxidize the pentitol-phosphates produced during PTS-catalyzed transport to the PPP intermediate xylulose-5-P. <i>L. monocytogenes</i> contains another PTS, which exhibits significant sequence identity to PTS<sup>Axl</sup>. Its genes are also part of an operon encoding PPP enzymes. Deletion of the EIIC-encoding gene <i>(lmo0508)</i> affected neither <smlcap>D</smlcap>-arabitol nor <smlcap>D</smlcap>-xylitol utilization, although <smlcap>D</smlcap>-arabitol induces the expression of this operon. Both operons are controlled by MtlR/LicR-type transcription activators (Lmo2668 and Lmo0501, respectively). Phosphorylation of Lmo0501 by the soluble PTS<sup>Axl</sup> components probably explains why <smlcap>D</smlcap>-arabitol also induces the second pentitol operon. Listerial virulence genes are submitted to strong repression by PTS sugars, such as glucose. However, <smlcap>D</smlcap>-arabitol inhibited virulence gene expression only at high concentrations, probably owing to its less efficient utilization compared to glucose.
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Maasjost, Julia, Dörte Lüschow, Anne Kleine, Hafez M. Hafez i Kristin Mühldorfer. "Presence of Virulence Genes in Enterococcus Species Isolated from Meat Turkeys in Germany Does Not Correlate with Chicken Embryo Lethality". BioMed Research International 2019 (30.10.2019): 1–10. http://dx.doi.org/10.1155/2019/6147695.
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Virulence-associated traits have frequently been studied in enterococci and are considered to contribute towards the pathogenicity of infections. In the present study, Enterococcus isolates were collected during diagnostic investigations from meat turkeys in Germany. Twenty-eight isolates of three different Enterococcus species were analyzed for five selected putative virulence traits to understand their potential role in the pathogenicity using the chicken embryo lethality assay. Ten E. faecalis, ten E. faecium, and eight E. gallinarum isolates were examined for the presence of common virulence genes and their phenotypic expression, namely, the cytolysin operon, five individual cyl genes (cylLL, cylLS, cylM, cylB, and cylA), gelatinase (gelE), hyaluronidase (hylEfm), aggregation substance (asa1), and enterococcal surface protein (esp). The Enterococcus isolates showed significant species-dependent differences in the presence of genotypic traits (p<0.001 by Fisher’s exact test; Cramer’s V = 0.68). At least one gene and up to three virulence traits were found in E. faecalis, while six E. faecium isolates and one E. gallinarum isolate did not display any virulence-associated pheno- or genotype. More than half of the Enterococcus isolates (n = 15) harbored the gelE gene, but only E. faecalis (n = 10) expressed the gelatinase activity in vitro. The hylEfm gene was found in five E. gallinarum isolates only, while seven isolates showed the hyaluronidase activity in the phenotypic assay. In Cramer’s V statistic, a moderate association was indicated for species (V ≤ 0.35) or genotype (V < 0.43) and the results from the embryo lethality assay, but the differences were not significant. All E. gallinarum isolates were less virulent with mortality rates ranging between 0 and 30%. Two E. faecalis isolates were highly virulent, harboring the whole cyl-operon as well as gelE and asa1 genes. Likewise, one E. faecium isolate caused high embryo mortality but did not harbor any of the investigated virulence genes. For the first time, Enterococcus isolates of three different species collected from diseased turkeys were investigated for their virulence properties in comparison. The results differed markedly between the Enterococcus species, with E. faecalis harboring the majority of investigated genes and virulence traits. However, the genotype did not entirely correlate with the phenotype or the isolates’ virulence potential and pathogenicity for chicken embryos.
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Cursino, Luciana, Cheryl D. Galvani, Dusit Athinuwat, Paulo A. Zaini, Yaxin Li, Leonardo De La Fuente, Harvey C. Hoch, Thomas J. Burr i Patricia Mowery. "Identification of an Operon, Pil-Chp, That Controls Twitching Motility and Virulence in Xylella fastidiosa". Molecular Plant-Microbe Interactions® 24, nr 10 (październik 2011): 1198–206. http://dx.doi.org/10.1094/mpmi-10-10-0252.
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Xylella fastidiosa is an important phytopathogenic bacterium that causes many serious plant diseases, including Pierce's disease of grapevines. Disease manifestation by X. fastidiosa is associated with the expression of several factors, including the type IV pili that are required for twitching motility. We provide evidence that an operon, named Pil-Chp, with genes homologous to those found in chemotaxis systems, regulates twitching motility. Transposon insertion into the pilL gene of the operon resulted in loss of twitching motility (pilL is homologous to cheA genes encoding kinases). The X. fastidiosa mutant maintained the type IV pili, indicating that the disrupted pilL or downstream operon genes are involved in pili function, and not biogenesis. The mutated X. fastidiosa produced less biofilm than wild-type cells, indicating that the operon contributes to biofilm formation. Finally, in planta the mutant produced delayed and less severe disease, indicating that the Pil-Chp operon contributes to the virulence of X. fastidiosa, presumably through its role in twitching motility.
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Navais, Roberto, Jessica Méndez, Pilar Reimundo, David Pérez-Pascual, Esther Gómez i José A. Guijarro. "TheyctCBAOperon ofYersinia ruckeri, Involved inIn VivoCitrate Uptake, Is Not Required for Virulence". Applied and Environmental Microbiology 77, nr 3 (3.12.2010): 1107–10. http://dx.doi.org/10.1128/aem.01808-10.
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ABSTRACTA three-gene operon, namedyctCBA(Yersiniacitratetransporter), induced by citrate and repressed by glucose was identified from a previously selectedin vivo-induced (ivi) clone in the fish pathogenYersiniaruckeri. Interestingly, despite being aniviclone, the drastic growth reduction of theyctCmutant in the presence of citrate, and the relatively high content of this compound in rainbow trout serum, the operon was not required for virulence.
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Kanjilal, Sanjat, Robert Citorik, Regina C. LaRocque, Marco F. Ramoni i Stephen B. Calderwood. "A Systems Biology Approach To Modeling Vibrio cholerae Gene Expression under Virulence-Inducing Conditions". Journal of Bacteriology 192, nr 17 (2.07.2010): 4300–4310. http://dx.doi.org/10.1128/jb.00182-10.
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ABSTRACT Vibrio cholerae is a Gram-negative bacillus that is the causative agent of cholera. Pathogenesis in vivo occurs through a series of spatiotemporally controlled events under the control of a gene cascade termed the ToxR regulon. Major genes in the ToxR regulon include the master regulators toxRS and tcpPH, the downstream regulator toxT, and virulence factors, the ctxAB and tcpA operons. Our current understanding of the dynamics of virulence gene expression is limited to microarray analyses of expression at selected time points. To better understand this process, we utilized a systems biology approach to examine the temporal regulation of gene expression in El Tor V. cholerae grown under virulence-inducing conditions in vitro (AKI medium), using high-resolution time series genomic profiling. Results showed that overall gene expression in AKI medium mimics that of in vivo studies but with less clear temporal separation between upstream regulators and downstream targets. Expression of toxRS was unaffected by growth under virulence-inducing conditions, but expression of toxT was activated shortly after switching from stationary to aerating conditions. The tcpA operon was also activated early during mid-exponential-phase growth, while the ctxAB operon was turned on later, after the rise in toxT expression. Expression of ctxAB continued to rise despite an eventual decrease in toxT. Cluster analysis of gene expression highlighted 15 hypothetical genes and six genes related to environmental information processing that represent potential new members of the ToxR regulon. This study applies systems biology tools to analysis of gene expression of V. cholerae in vitro and provides an important comparator for future studies done in vivo.
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Berdichevsky, Tatiana, Devorah Friedberg, Chen Nadler, Assaf Rokney, Amos Oppenheim i Ilan Rosenshine. "Ler Is a Negative Autoregulator of the LEE1 Operon in Enteropathogenic Escherichia coli". Journal of Bacteriology 187, nr 1 (1.01.2005): 349–57. http://dx.doi.org/10.1128/jb.187.1.349-357.2005.
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ABSTRACT Enteropathogenic Escherichia coli (EPEC) causes severe diarrhea in young children. Essential for colonization of the host intestine is the LEE pathogenicity island, which comprises a cluster of operons encoding a type III secretion system and related proteins. The LEE1 operon encodes Ler, which positively regulates many EPEC virulence genes in the LEE region and elsewhere in the chromosome. We found that Ler acts as a specific autorepressor of LEE1 transcription. We further show that Ler specifically binds upstream of the LEE1 operon in vivo and in vitro. A comparison of the Ler affinities to different DNA regions suggests that the autoregulation mechanism limits the steady-state level of Ler to concentrations that are just sufficient for activation of the LEE2 and LEE3 promoters and probably other LEE promoters. This mechanism may reflect the need of EPEC to balance maximizing the colonization efficiency by increasing the expression of the virulence genes and minimizing the immune response of the host by limiting their expression. In addition, we found that the autoregulation mechanism reduces the cell-to-cell variability in the levels of LEE1 expression. Our findings point to a new negative regulatory circuit that suppresses the noise and optimizes the expression levels of ler and other LEE1 genes.
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Miguel-Arribas, Andrés, Jorge Val-Calvo, César Gago-Córdoba, José M. Izquierdo, David Abia, Ling Juan Wu, Jeff Errington i Wilfried J. J. Meijer. "A novel bipartite antitermination system widespread in conjugative elements of Gram-positive bacteria". Nucleic Acids Research 49, nr 10 (17.05.2021): 5553–67. http://dx.doi.org/10.1093/nar/gkab360.
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Abstract Transcriptional regulation allows adaptive and coordinated gene expression, and is essential for life. Processive antitermination systems alter the transcription elongation complex to allow the RNA polymerase to read through multiple terminators in an operon. Here, we describe the discovery of a novel bipartite antitermination system that is widespread among conjugative elements from Gram-positive bacteria, which we named conAn. This system is composed of a large RNA element that exerts antitermination, and a protein that functions as a processivity factor. Besides allowing coordinated expression of very long operons, we show that these systems allow differential expression of genes within an operon, and probably contribute to strict regulation of the conjugation genes by minimizing the effects of spurious transcription. Mechanistic features of the conAn system are likely to decisively influence its host range, with important implications for the spread of antibiotic resistance and virulence genes.
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González, Enid T., i Caitilyn Allen. "Characterization of a Ralstonia solanacearum Operon Required for Polygalacturonate Degradation and Uptake of Galacturonic Acid". Molecular Plant-Microbe Interactions® 16, nr 6 (czerwiec 2003): 536–44. http://dx.doi.org/10.1094/mpmi.2003.16.6.536.
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The bacterial wilt pathogen Ralstonia solanacearum produces three extracellular polygalacturonases (PGs): PehA, PehB, and PehC. All three PGs hydrolyze pectin's polygalacturonic acid backbone, but each releases different reaction products. PehA and PehB contribute significantly to pathogen virulence, probably by facilitating root invasion and colonization. To determine the collective contribution of PGs to virulence and saprophytic survival, we cloned, characterized, and mutated the R. solanacearum pehC gene, which encodes a distinctive monogalacturonate-releasing exo-PG. The virulence of a pehC mutant on tomato was indistinguishable from that of its wild-type parent; thus, this exo-PG alone does not contribute significantly to wilt pathogenesis. Unexpectedly, a completely PG-deficient triple pehA/B/C mutant was slightly more virulent than a pehA/B mutant. PehC may degrade galacturonide elicitors of host defense, thereby protecting the pathogen from plant antimicrobial responses. A galacturonate transporter gene, exuT, is immediately downstream of pehC and the two genes are co-transcribed. It has been hypothesized that galacturonic acid released by PGs from plant cell walls nourishes bacteria during pathogenesis. To separate the pectolytic and nutrient-generating roles of the PGs, we made an exuT mutant, which still produces all three isozymes of PG but cannot uptake PG degradation products. This exuT mutant had wild-type virulence on tomato, demonstrating that metabolism of galacturonic acid does not contribute significantly to bacterial success inside the plant.
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Abi Khattar, Z., A. Rejasse, D. Destoumieux-Garzón, J. M. Escoubas, V. Sanchis, D. Lereclus, A. Givaudan, M. Kallassy, C. Nielsen-Leroux i S. Gaudriault. "The dlt Operon of Bacillus cereus Is Required for Resistance to Cationic Antimicrobial Peptides and for Virulence in Insects". Journal of Bacteriology 191, nr 22 (18.09.2009): 7063–73. http://dx.doi.org/10.1128/jb.00892-09.
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ABSTRACT The dlt operon encodes proteins that alanylate teichoic acids, the major components of cell walls of gram-positive bacteria. This generates a net positive charge on bacterial cell walls, repulsing positively charged molecules and conferring resistance to animal and human cationic antimicrobial peptides (AMPs) in gram-positive pathogenic bacteria. AMPs damage the bacterial membrane and are the most effective components of the humoral immune response against bacteria. We investigated the role of the dlt operon in insect virulence by inactivating this operon in Bacillus cereus, which is both an opportunistic human pathogen and an insect pathogen. The ΔdltBc mutant displayed several morphological alterations but grew at a rate similar to that for the wild-type strain. This mutant was less resistant to protamine and several bacterial cationic AMPs, such as nisin, polymyxin B, and colistin, in vitro. It was also less resistant to molecules from the insect humoral immune system, lysozyme, and cationic AMP cecropin B from Spodoptera frugiperda. ΔdltBc was as pathogenic as the wild-type strain in oral infections of Galleria mellonella but much less virulent when injected into the hemocoels of G. mellonella and Spodoptera littoralis. We detected the dlt operon in three gram-negative genera: Erwinia (Erwinia carotovora), Bordetella (Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica), and Photorhabdus (the entomopathogenic bacterium Photorhabdus luminescens TT01, the dlt operon of which did not restore cationic AMP resistance in ΔdltBc ). We suggest that the dlt operon protects B. cereus against insect humoral immune mediators, including hemolymph cationic AMPs, and may be critical for the establishment of lethal septicemia in insects and in nosocomial infections in humans.
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Madrid, Cristina, José M. Nieto, Sònia Paytubi, Maurizio Falconi, Claudio O. Gualerzi i Antonio Juárez. "Temperature- and H-NS-Dependent Regulation of a Plasmid-Encoded Virulence Operon Expressing Escherichia coli Hemolysin". Journal of Bacteriology 184, nr 18 (15.09.2002): 5058–66. http://dx.doi.org/10.1128/jb.184.18.5058-5066.2002.
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ABSTRACT Proteins H-NS and Hha form a nucleoprotein complex that modulates expression of the thermoregulated hly operon of Escherichia coli. We have been able to identify two H-NS binding sites in the hly regulatory region. One of them partially overlaps the promoter region (site II), and the other is located about 2 kbp upstream (site I). In contrast, Hha protein did not show any preference for specific sequences. In vitro, temperature influences the affinity of H-NS for a DNA fragment containing both binding sites and H-NS-mediated repression of hly operon transcription. Deletion analysis of the hly regulatory region confirms the relevance of site I for thermoregulation of this operon. We present a model to explain the temperature-modulated repression of the hly operon, based on the experiments reported here and other, preexisting data.
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Bernier, Christine, Pierre Gounon i Chantal Le Bouguénec. "Identification of an Aggregative Adhesion Fimbria (AAF) Type III-Encoding Operon in Enteroaggregative Escherichia coli as a Sensitive Probe for Detecting the AAF-Encoding Operon Family". Infection and Immunity 70, nr 8 (sierpień 2002): 4302–11. http://dx.doi.org/10.1128/iai.70.8.4302-4311.2002.
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ABSTRACT Enteroaggregative Escherichia coli (EAEC) is recognized as an emerging cause of diarrhea in children and adults worldwide, and recent studies have implicated EAEC in persistent diarrhea in patients infected with human immunodeficiency virus (HIV). In this study, we identified aggregative adhesion fimbria type III (AAF-III) in isolate 55989, a typical EAEC strain. Analysis of the sequence of the plasmid-borne agg-3 gene cluster encoding AAF-III showed this cluster to be closely related to the agg and aaf operons and to the afa operons carried by diffusely adherent pathogenic E. coli. We investigated the adhesion properties of a collection of 25 EAEC strains isolated from HIV-infected patients presenting with persistent diarrhea. We found that a minority of strains (36%) carried sequences similar to those of the agg and aaf operons, which encode AAF-I and AAF-II, respectively. We developed PCR assays specific for the agg-3 operon. In our collection, the frequency of AAF-III strains was similar (12%) to that of AAF-I strains (16%) but higher than that of AAF-II isolates (0%). Differences between EAEC strains in terms of the virulence factors present render detection of these strains difficult with the available DNA probes. Based on comparison of the agg, aaf, and agg-3 operons, we defined an AAF probe internal to the adhesion gene clusters and demonstrated that it was efficient for the identification of EAEC strains. We investigated 32 EAEC isolates, of which only 34.4% were detected with the classical CVD432 probe (detecting pAA virulence plasmids) whereas 65.6% were detected with the AAF probe.
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M�ndez, J., L. Fern�ndez, A. Men�ndez, P. Reimundo, D. P�rez-Pascual, R. Navais i J. A. Guijarro. "A Chromosomally Located traHIJKCLMN Operon Encoding a Putative Type IV Secretion System Is Involved in the Virulence of Yersinia ruckeri". Applied and Environmental Microbiology 75, nr 4 (16.12.2008): 937–45. http://dx.doi.org/10.1128/aem.01377-08.
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ABSTRACT Nucleotide sequence analysis of the region surrounding the pIVET8 insertion site in Yersinia ruckeri 150RiviXII, previously selected by in vivo expression technology (IVET), revealed the presence of eight genes (traHIJKCLMN [hereafter referred to collectively as the tra operon or tra cluster]), which are similar both in sequence and organization to the tra operon cluster found in the virulence-related plasmid pADAP from Serratia entomophila. Interestingly, the tra cluster of Y. ruckeri is chromosomally encoded, and no similar tra cluster has been identified yet in the genomic analysis of human pathogenic yersiniae. A traI insertional mutant was obtained by homologous recombination. Coinfection experiments with the mutant and the parental strain, as well as 50% lethal dose determinations, indicate that this operon is involved in the virulence of this bacterium. All of these results suggest the implication of the tra cluster in a virulence-related type IV secretion/transfer system. Reverse transcriptase PCR studies showed that this cluster is transcribed as an operon from a putative promoter located upstream of traH and that the mutation of traI had a polar effect. A traI::lacZY transcriptional fusion displayed higher expression levels at 18�C, the temperature of occurrence of the disease, and under nutrient-limiting conditions. PCR detection analysis indicated that the tra cluster is present in 15 Y. ruckeri strains from different origins and with different plasmid profiles. The results obtained in the present study support the conclusion, already suggested by different authors, that Y. ruckeri is a very homogeneous species that is quite different from the other members of the genus Yersinia.
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Fink, Ryan C., Matthew R. Evans, Steffen Porwollik, Andres Vazquez-Torres, Jessica Jones-Carson, Bryan Troxell, Stephen J. Libby, Michael McClelland i Hosni M. Hassan. "FNR Is a Global Regulator of Virulence and Anaerobic Metabolism in Salmonella enterica Serovar Typhimurium (ATCC 14028s)". Journal of Bacteriology 189, nr 6 (12.01.2007): 2262–73. http://dx.doi.org/10.1128/jb.00726-06.
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ABSTRACT Salmonella enterica serovar Typhimurium must successfully transition the broad fluctuations in oxygen concentrations encountered in the host. In Escherichia coli, FNR is one of the main regulatory proteins involved in O2 sensing. To assess the role of FNR in serovar Typhimurium, we constructed an isogenic fnr mutant in the virulent wild-type strain (ATCC 14028s) and compared their transcriptional profiles and pathogenicities in mice. Here, we report that, under anaerobic conditions, 311 genes (6.80% of the genome) are regulated directly or indirectly by FNR; of these, 87 genes (28%) are poorly characterized. Regulation by FNR in serovar Typhimurium is similar to, but distinct from, that in E. coli. Thus, genes/operons involved in aerobic metabolism, NO· detoxification, flagellar biosynthesis, motility, chemotaxis, and anaerobic carbon utilization are regulated by FNR in a fashion similar to that in E. coli. However, genes/operons existing in E. coli but regulated by FNR only in serovar Typhimurium include those coding for ethanolamine utilization, a universal stress protein, a ferritin-like protein, and a phosphotransacetylase. Interestingly, Salmonella-specific genes/operons regulated by FNR include numerous virulence genes within Salmonella pathogenicity island 1 (SPI-1), newly identified flagellar genes (mcpAC, cheV), and the virulence operon (srfABC). Furthermore, the role of FNR as a positive regulator of motility, flagellar biosynthesis, and pathogenesis was confirmed by showing that the mutant is nonmotile, lacks flagella, is attenuated in mice, and does not survive inside macrophages. The inability of the mutant to survive inside macrophages is likely due to its sensitivity to the reactive oxygen species generated by NADPH phagocyte oxidase.
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Reed, Samantha B., Carla A. Wesson, Linda E. Liou, William R. Trumble, Patrick M. Schlievert, Gregory A. Bohach i Kenneth W. Bayles. "Molecular Characterization of a NovelStaphylococcus aureus Serine Protease Operon". Infection and Immunity 69, nr 3 (1.03.2001): 1521–27. http://dx.doi.org/10.1128/iai.69.3.1521-1527.2001.
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ABSTRACT The present study identified and characterized a unique operon (spl) encoding six serine protease-like proteins. In addition, native Spl proteins were isolated and characterized. Typical of most exoproteins, the spl gene products contain putative 35- or 36-amino-acid signal peptides. The Spl proteins share 44 to 95% amino acid sequence identity with each other and 33 to 36% sequence identity with V8 protease. They also contain amino acids found in catalytic triads of enzymes in the trypsin-like serine protease family, and SplB and SplC were shown to degrade casein. The sploperon is transcribed on a 5.5-kb transcript, but several nonrandom degradation products of this transcript were also identified. Similar to other S. aureus exoprotein genes, the sploperon is maximally expressed during the transition into stationary phase and is positively controlled by the Agr virulence factor regulator. The Sar regulatory system did not affect sploperon expression. PCR analysis revealed the presence of thespl operon in 64% of the S. aureus isolates tested, although one spl operon-negative isolate was shown to contain at least two of the spl genes. Finally, intraperitoneal injection of an spl operon deletion mutant revealed no major differences in virulence compared to the parental strain.
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Papazisi, L., S. Frasca, M. Gladd, X. Liao, D. Yogev i S. J. Geary. "GapA and CrmA Coexpression Is Essential for Mycoplasma gallisepticum Cytadherence and Virulence". Infection and Immunity 70, nr 12 (grudzień 2002): 6839–45. http://dx.doi.org/10.1128/iai.70.12.6839-6845.2002.
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ABSTRACT It was previously demonstrated that avirulent Mycoplasma gallisepticum strain Rhigh (passage 164) is lacking three proteins that are expressed in its virulent progenitor, strain Rlow (passage 15). These proteins were identified as the cytadhesin molecule GapA, the putative cytadhesin-related molecule CrmA, and a component of a high-affinity transporter system, HatA. Complementation of Rhigh with wild-type gapA restored expression in the transformant (GT5) but did not restore the cytadherence phenotype and maintained avirulence in chickens. These results suggested that CrmA might play an essential role in the M. gallisepticum cytadherence process. CrmA is encoded by the second gene in the gapA operon and shares significant sequence homology to the ORF6 gene of Mycoplasma pneumoniae, which has been shown to play an accessory role in the cytadherence process. Complementation of Rhigh with wild-type crmA resulted in the transformant (SDCA) that lacked the cytadherence and virulence phenotype comparable to that found in Rhigh and GT5. In contrast, complementation of Rhigh with the entire wild-type gapA operon resulted in the transformant (GCA1) that restored cytadherence to the level found in wild-type Rlow. In vivo pathogenesis trials revealed that GCA1 had regained virulence, causing airsacculitis in chickens. These results demonstrate that both GapA and CrmA are required for M. gallisepticum cytadherence and pathogenesis.
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Jaafar, Firas Nabeeh, Majid Ahmed AL-Bayati, Hadeel Kareem Musafer, Maan Abdul Azeez i Zahraa Kareem Raheem. "Quorum Sensing and its Correlation with Virulence Factors". South Asian Research Journal of Pharmaceutical Sciences 4, nr 3 (10.06.2022): 60–69. http://dx.doi.org/10.36346/sarjps.2022.v04i03.003.
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Quorum sensing (QS) is cell to cell signaling mechanism that enables bacteria collectively control gene expression in response to their population density, or it is bacterial communicate with one another using chemical signals. There are three types of signaling molecules: Acyl-homoserinelactonase (AHLs), Auto-inducer peptides (AIPs) and Autoinducer-2 (AI-2). Q.S was first observed and described in bioluminescence bacterium V.fischeri.In V. fischeri, several kinds of quorum sensing system were identified. At first, lux system was found and regulates the luciferase operon and light production. LuxIwas isolated as an AHL synthase while LuxR was isolated as a transcriptional activator of the luciferase operon. At low cell density, LuxOrepresses LitR, which is a positive regulator of the expression of LuxR. Quorum quenching (QQ) refers to the mechanism by which bacterial communication can be interrupted, or it is the process of preventing QS by disrupting the signaling.The first major QS-disrupting strategy that has been studied is the interference with the detection of the AIs and the second one is the inactivation/degradations of the signal molecules.
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Flego, Diana, Reet Marits, Anders R. B. Eriksson, Viia Kõiv, Maj-Brit Karlsson, Riikka Heikinheimo i E. Tapio Palva. "A Two-Component Regulatory System, pehR-pehS, Controls Endopolygalacturonase Production and Virulence in the Plant Pathogen Erwinia carotovora subsp. carotovora". Molecular Plant-Microbe Interactions® 13, nr 4 (kwiecień 2000): 447–55. http://dx.doi.org/10.1094/mpmi.2000.13.4.447.
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Genes coding for the main virulence determinants of the plant pathogen Erwinia carotovora subsp. carotovora, the plant cell wall-degrading enzymes, are under the coordinate control of global regulator systems including both positive and negative factors. In addition to this global control, some virulence determinants are subject to specific regulation. We have previously shown that mutations in the pehR locus result in reduced virulence and impaired production of one of these enzymes, an endopolygalacturonase (PehA). In contrast, these pehR strains produce essentially wild-type levels of other extracellular enzymes including pectate lyases and cellulases. In this work, we characterized the pehR locus and showed that the DNA sequence is composed of two genes, designated pehR and pehS, present in an operon. Mutations in either pehR or pehS caused a Peh-negative phenotype and resulted in reduced virulence on tobacco seedlings. Complementation experiments indicated that both genes are required for transcriptional activation of the endopolygalacturonase gene, pehA, as well as restoration of virulence. Structural characterization of the pehR-pehS operon demonstrated that the corresponding polypeptides are highly similar to the two-component transcriptional regulators PhoP-PhoQ of both Escherichia coli and Salmonella typhimurium. Functional similarity of PehR-PehS with PhoP-PhoQ of E. coli and S. typhimurium was demonstrated by genetic complementation.
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Steiner, Kerstin, i Horst Malke. "relA-Independent Amino Acid Starvation Response Network of Streptococcus pyogenes". Journal of Bacteriology 183, nr 24 (15.12.2001): 7354–64. http://dx.doi.org/10.1128/jb.183.24.7354-7364.2001.
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ABSTRACT Streptococcus pyogenes (group A streptococcus [GAS]), a multiple-amino-acid-auxotrophic human pathogen, may face starvation for essential amino acids during various stages of the infection process. Since the response of GAS to such conditions is likely to influence pathogenetic processes, we set out to identify by transcriptional analyses genes and operons that are responsive to amino acid starvation and examined whether functionally meaningful response patterns can be ascertained. We discovered that GAS are capable of mounting a relA-independent amino acid starvation response that involves transcriptional modulation of a wide array of housekeeping genes as well as accessory and dedicated virulence genes. Housekeeping genes that were upregulated during starvation of both wild-type and relA mutant strains included the newly identified T-box members of the aminoacyl-tRNA synthetase genes, the genes for components of the tmRNA-mediated peptide tagging and proteolysis system for abnormal proteins (ssrA, smpB,clpP, and clpC), and the operons for thednaK and groE groups of molecular chaperones. In addition to upregulation of the genes for oligopeptide permease (opp), intracellular peptidase (pepB), and the two-component regulatorcovRS reported previously (K. Steiner and H. Malke, Mol. Microbiol. 38:1004–1016, 2000), amino acid starvation stimulated the transcription of the growth phase-associated, virulence-regulatory fas operon, the streptolysin S operon (sag), and the gene for autoinducer-2 production protein (luxS). A prominent feature of operons exhibiting internal transcriptional termination (opp, fas, andsag) was starvation-promoted full-length transcription, a mechanism that improves the efficacy of these systems by increasing the level of coordinate transcription of functionally related genes. Based on these results, a regulatory network with feedback mechanisms is proposed that counteracts the stringent response, links the levels of key rate-limiting enzymes to virulence gene expression, and enables the organism in a dynamic way to take advantage of protein-rich environments provided by its human host. As several of the affected target genes are controlled by more than one regulator, fine modulation may result in accordance with the demands imposed by ecologically different colonization sites upon the adaptive capacity of the pathogen.
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Samen, Ulrike M., Bernhard J. Eikmanns i Dieter J. Reinscheid. "The Transcriptional Regulator RovS Controls the Attachment of Streptococcus agalactiae to Human Epithelial Cells and the Expression of Virulence Genes". Infection and Immunity 74, nr 10 (październik 2006): 5625–35. http://dx.doi.org/10.1128/iai.00667-06.
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ABSTRACT Streptococcus agalactiae is part of the normal flora of the human gastrointestinal tract and also the leading cause of bacterial infections in human newborns and immunocompromised adults. The colonization and infection of different regions within the human host require a regulatory network in S. agalactiae that senses environmental stimuli and controls the formation of specific virulence factors. In the present study, we characterized an Rgg-like transcriptional regulator, designated RovS (regulator of virulence in Streptococcus agalactiae). Deletion of the rovS gene in the genome of S. agalactiae resulted in strain 6313 ΔrovS, which exhibited an increased attachment to immobilized fibrinogen and a significant increase in adherence to the eukaryotic lung epithelial cell line A549. Quantification of expression levels of known and putative S. agalactiae virulence genes by real-time PCR revealed that RovS influences the expression of fbsA, gbs0230, sodA, rogB, and the cyl operon. The altered gene expression in mutant 6313 ΔrovS was restored by plasmid-mediated expression of rovS, confirming the RovS deficiency as the cause for the observed changes in virulence gene expression in S. agalactiae. DNA electrophoretic mobility shift assays showed that RovS specifically binds to the promoter regions of fbsA, gbs0230, sodA, and the cyl operon, indicating that RovS directly regulates their expression. Deletion and mutation studies in the promoter region of fbsA, encoding the main fibrinogen receptor in S. agalactiae, identified a RovS DNA motif. Similar motifs were also found in the promoter regions of gbs0230, sodA, and the cyl operon, and alignments allowed us to propose a consensus sequence for the DNA-binding site of RovS.
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Ho, Theresa D., i James M. Slauch. "Characterization of grvA, an Antivirulence Gene on the Gifsy-2 Phage in Salmonella enterica Serovar Typhimurium". Journal of Bacteriology 183, nr 2 (15.01.2001): 611–20. http://dx.doi.org/10.1128/jb.183.2.611-620.2001.
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ABSTRACT The lambdoid phage Gifsy-2 contributes significantly toSalmonella enterica serovar Typhimurium virulence. The phage carries the periplasmic superoxide dismutase gene,sodCI, and other unidentified virulence factors. We have characterized the gene grvA, a single open reading frame inserted in the opposite orientation in the tail operon of the Gifsy-2 phage. Contrary to what is observed with classic virulence genes,grvA null mutants were more virulent than wild type as measured by intraperitoneal competition assays in mice. We have termed this effect antivirulence. Wild-type grvA in single copy complemented this phenotype. However, grvA +on a multicopy plasmid also conferred the antivirulence phenotype. Neither a grvA null mutation nor thegrvA + plasmid conferred a growth advantage or disadvantage in laboratory media. The antivirulence phenotype conferred by the grvA null mutation and thegrvA + plasmid required wild-typesodCI but was independent of other virulence factors encoded on Gifsy-2. These results suggest that in a wild-type situation, GrvA decreases the pathogenicity of serovar Typhimurium in the host, most likely by affecting resistance to toxic oxygen species. These virulence phenotypes were independent of functional Gifsy-2 phage production. Our data suggest that the contribution of Gifsy-2 is a complicated sum of both positive virulence factors such assodCI and antivirulence factors such asgrvA.
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Lee, E. J., J. Choi i E. A. Groisman. "Control of a Salmonella virulence operon by proline-charged tRNAPro". Proceedings of the National Academy of Sciences 111, nr 8 (10.02.2014): 3140–45. http://dx.doi.org/10.1073/pnas.1316209111.
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Lee, Eun‐Jin, i Eduardo A. Groisman. "Tandem attenuators control expression of the Salmonella mgtCBR virulence operon". Molecular Microbiology 86, nr 1 (26.08.2012): 212–24. http://dx.doi.org/10.1111/j.1365-2958.2012.08188.x.
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Bretl, Daniel J., Hongjun He, Crystalla Demetriadou, Mark J. White, Renee M. Penoske, Nita H. Salzman i Thomas C. Zahrt. "MprA and DosR Coregulate a Mycobacterium tuberculosis Virulence Operon EncodingRv1813candRv1812c". Infection and Immunity 80, nr 9 (11.06.2012): 3018–33. http://dx.doi.org/10.1128/iai.00520-12.
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ABSTRACTMycobacterium tuberculosisremains a significant global pathogen, causing extensive morbidity and mortality worldwide. This bacterium persists within granulomatous lesions in a poorly characterized, nonreplicating state. The two-component signal transduction systems MprAB and DosRS-DosT (DevRS-Rv2027c) are responsive to conditions likely to be present within granulomatous lesions and mediate aspects ofM. tuberculosispersistencein vitroandin vivo. Here, we describe a previously uncharacterized locus,Rv1813c-Rv1812c, that is coregulated by both MprA and DosR. We demonstrate that MprA and DosR bind to adjacent and overlapping sequences within the promoter region ofRv1813cand direct transcription from an initiation site located several hundred base pairs upstream of theRv1813translation start site. We further show thatRv1813candRv1812care cotranscribed, and that the genomic organization of this operon is specific toM. tuberculosisandMycobacterium bovis. AlthoughRv1813cis not required for survival ofM. tuberculosisin vitro, including under conditions in which MprAB and DosRST signaling are activated, anM. tuberculosisΔRv1813cmutant is attenuated in the low-dose aerosol model of murine tuberculosis, where it exhibits a lower bacterial burden, delayed time to death, and decreased ability to stimulate proinflammatory cytokines interleukin-1β (IL-1β) and IL-12. Interestingly, overcomplementation of these phenotypes is observed in theM. tuberculosisΔRv1813cmutant expressing bothRv1813candRv1812c, but notRv1813calone, intrans. Therefore, Rv1813c and Rv1812c may represent general stress-responsive elements that are necessary for aspects ofM. tuberculosisvirulence and the host immune response to infection.
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Qin, Aiping, David W. Scott i Barbara J. Mann. "Francisella tularensis subsp. tularensis Schu S4 Disulfide Bond Formation Protein B, but Not an RND-Type Efflux Pump, Is Required for Virulence". Infection and Immunity 76, nr 7 (5.05.2008): 3086–92. http://dx.doi.org/10.1128/iai.00363-08.
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ABSTRACT Francisella tularensis subsp. tularensis is a highly virulent bacterium that is a CDC select agent. Despite advancements in the understanding of its biology, details pertaining to virulence are poorly understood. In previous work, we identified a transposon insertion mutant in the FTT0107c locus that was defective in intracellular survival in HepG2 and J77A.1 cells. Here, we report that this mutant was also highly attenuated in vivo. The FTT0107c locus is predicted to encode an ortholog of the disulfide bond formation B protein (DsbB). This designation was confirmed by complementation of an Escherichia coli dsbB mutant. This dsbB mutant of Schu S4 was highly attenuated in mice, but unlike what has been reported for Francisella novicida, intranasal immunization with a sublethal dose did not induce protection against wild-type challenge. dsbB was found to be transcribed in an operon with acrA and acrB, which encode an RND-type efflux pump. However, this pump did not make a significant contribution to virulence because strains with nonpolar deletions in acrA and acrB behaved like wild-type strain Schu S4 with respect to intracellular growth and in vivo virulence. This result is in contrast to a report that an acrB mutant of a live vaccine strain of F. tularensis has decreased virulence in mice. Overall, these results demonstrate key differences between the virulence requirements of Schu S4 and less virulent subspecies of Francisella. We have shown that DsbB is a key participant in intracellular growth and virulence, and our results suggest that there are critical virulence factors that contain disulfide bonds.
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Wagner, Christian, Antoine de Saizieu, Hans-Joachim Schönfeld, Markus Kamber, Roland Lange, Charles J. Thompson i Malcolm G. Page. "Genetic Analysis and Functional Characterization of the Streptococcus pneumoniae vic Operon". Infection and Immunity 70, nr 11 (listopad 2002): 6121–28. http://dx.doi.org/10.1128/iai.70.11.6121-6128.2002.
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ABSTRACT The vic two-component signal transduction system of Streptococcus pneumoniae is essential for growth. The vic operon comprises three genes encoding the following: VicR, a response regulator of the OmpR family; VicK, its cognate histidine kinase; and VicX, a putative protein sharing 55% identity to the predicted product (YycJ) of an open reading frame in the Bacillus subtilis genome. We show that not only is vic essential for viability but it also influences virulence and competence. A putative transcriptional start site for the vic operon was mapped 16 bp upstream of the ATG codon of vicR. Only one transcript of 2.9 kb, encoding all three genes, was detected by Northern blot analysis. VicK, an atypical PAS domain-containing histidine kinase, can be autophosphorylated in vitro, and VicR functions in vitro as a phospho-acceptor protein. (PAS is an acronym formed from the names of the proteins in which the domains were first recognized: the Drosophila period clock protein [PER], vertebrate aryl hydrocarbon receptor nuclear translocator [ARNT], and Drosophila single-minded protein [SIM].) PAS domains are commonly involved in sensing intracellular signals such as redox potential, which suggests that the signal for vic might also originate in the cytoplasm. Growth rate, competence, and virulence were monitored in strains with mutations in the vic operon. Overexpression of the histidine kinase, VicK, resulted in decreased virulence, whereas the transformability of a null mutant decreased by 3 orders of magnitude.