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Control of Francisella tularensis Virulence at Gene Level: Network of Transcription Factors. Microorganisms 2020; 8:microorganisms8101622. [PMID: 33096715 PMCID: PMC7588896 DOI: 10.3390/microorganisms8101622] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2020] [Revised: 10/14/2020] [Accepted: 10/18/2020] [Indexed: 02/07/2023] Open
Abstract
Regulation of gene transcription is the initial step in the complex process that controls gene expression within bacteria. Transcriptional control involves the joint effort of RNA polymerases and numerous other regulatory factors. Whether global or local, positive or negative, regulators play an essential role in the bacterial cell. For instance, some regulators specifically modify the transcription of virulence genes, thereby being indispensable to pathogenic bacteria. Here, we provide a comprehensive overview of important transcription factors and DNA-binding proteins described for the virulent bacterium Francisella tularensis, the causative agent of tularemia. This is an unexplored research area, and the poorly described networks of transcription factors merit additional experimental studies to help elucidate the molecular mechanisms of pathogenesis in this bacterium, and how they contribute to disease.
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Oh KW, Kim K, Islam MM, Jung HW, Lim D, Lee JC, Shin M. Transcriptional Regulation of the Outer Membrane Protein A in Acinetobacter baumannii. Microorganisms 2020; 8:microorganisms8050706. [PMID: 32403355 PMCID: PMC7284552 DOI: 10.3390/microorganisms8050706] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 05/05/2020] [Accepted: 05/08/2020] [Indexed: 01/19/2023] Open
Abstract
Acinetobacter baumannii is known for its virulence in severely ill, hospitalized patients and for exhibiting multidrug resistance. A. baumannii infection treatment poses a serious problem in clinical environments. The outer membrane protein A (OmpA) of the Acinetobacter genus is involved in bacterial virulence. Regulatory factors of OmpA in the post-transcriptional stage have been previously identified. However, the regulatory factors that act before the transcriptional stage remain unclear. We investigated the A1S_0316 gene that encodes a putative transcription factor for OmpA expression in A. baumannii. A1S_0316 was purified and examined using size-exclusion chromatography, which revealed that it forms an oligomer. The binding affinity of A1S_0316 to the OmpA promoter region was also examined. We compared the binding affinity to the OmpA promotor region between A1S_0316 and the AbH-NS protein. A1S_0316 showed higher binding affinity to the OmpA promotor region than did H-NS. We examined the regulatory effect of these proteins on OmpA expression in A. baumannii using real-time qPCR and various in vitro tools. Our results indicated that A1S_0316 acts as an anti-repressor on the promotor region of the OmpA gene by inhibiting the binding of the AbH-NS protein. This study was the first demonstration of the transcriptional regulation of OmpA expression.
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Affiliation(s)
- Kyu-Wan Oh
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
| | - Kyeongmin Kim
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
| | - Md. Maidul Islam
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
| | - Hye-Won Jung
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
| | - Daejin Lim
- Department of Microbiology, School of Medicine, Chonnam National University, Gwangju 61468, Korea;
| | - Je Chul Lee
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
| | - Minsang Shin
- Department of Microbiology, School of Medicine, Kyungpook National University, 680 Gukchaebosang-ro, Jung-gu, Daegu 41944, Korea; (K.-W.O.); (K.K.); (M.M.I.); (H.-W.J.); (J.C.L.)
- Correspondence: ; Tel.: +82-53-420-4841
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Steele S, Radlinski L, Taft-Benz S, Brunton J, Kawula TH. Trogocytosis-associated cell to cell spread of intracellular bacterial pathogens. eLife 2016; 5. [PMID: 26802627 PMCID: PMC4786427 DOI: 10.7554/elife.10625] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Accepted: 01/22/2016] [Indexed: 11/13/2022] Open
Abstract
Macrophages are myeloid-derived phagocytic cells and one of the first immune cell types to respond to microbial infections. However, a number of bacterial pathogens are resistant to the antimicrobial activities of macrophages and can grow within these cells. Macrophages have other immune surveillance roles including the acquisition of cytosolic components from multiple types of cells. We hypothesized that intracellular pathogens that can replicate within macrophages could also exploit cytosolic transfer to facilitate bacterial spread. We found that viable Francisella tularensis, as well as Salmonella enterica bacteria transferred from infected cells to uninfected macrophages along with other cytosolic material through a transient, contact dependent mechanism. Bacterial transfer occurred when the host cells exchanged plasma membrane proteins and cytosol via a trogocytosis related process leaving both donor and recipient cells intact and viable. Trogocytosis was strongly associated with infection in mice, suggesting that direct bacterial transfer occurs by this process in vivo.
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Affiliation(s)
- Shaun Steele
- University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Lauren Radlinski
- University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Sharon Taft-Benz
- University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Jason Brunton
- University of North Carolina at Chapel Hill, Chapel Hill, United States
| | - Thomas H Kawula
- University of North Carolina at Chapel Hill, Chapel Hill, United States
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Kingry LC, Petersen JM. Comparative review of Francisella tularensis and Francisella novicida. Front Cell Infect Microbiol 2014; 4:35. [PMID: 24660164 PMCID: PMC3952080 DOI: 10.3389/fcimb.2014.00035] [Citation(s) in RCA: 142] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 02/22/2014] [Indexed: 01/08/2023] Open
Abstract
Francisella tularensis is the causative agent of the acute disease tularemia. Due to its extreme infectivity and ability to cause disease upon inhalation, F. tularensis has been classified as a biothreat agent. Two subspecies of F. tularensis, tularensis and holarctica, are responsible for tularemia in humans. In comparison, the closely related species F. novicida very rarely causes human illness and cases that do occur are associated with patients who are immune compromised or have other underlying health problems. Virulence between F. tularensis and F. novicida also differs in laboratory animals. Despite this varying capacity to cause disease, the two species share ~97% nucleotide identity, with F. novicida commonly used as a laboratory surrogate for F. tularensis. As the F. novicida U112 strain is exempt from U.S. select agent regulations, research studies can be carried out in non-registered laboratories lacking specialized containment facilities required for work with virulent F. tularensis strains. This review is designed to highlight phenotypic (clinical, ecological, virulence, and pathogenic) and genomic differences between F. tularensis and F. novicida that warrant maintaining F. novicida and F. tularensis as separate species. Standardized nomenclature for F. novicida is critical for accurate interpretation of experimental results, limiting clinical confusion between F. novicida and F. tularensis and ensuring treatment efficacy studies utilize virulent F. tularensis strains.
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Affiliation(s)
- Luke C Kingry
- Division of Vector-Borne Diseases, Bacterial Diseases Branch, Centers for Disease Control and Prevention Fort Collins, CO, USA
| | - Jeannine M Petersen
- Division of Vector-Borne Diseases, Bacterial Diseases Branch, Centers for Disease Control and Prevention Fort Collins, CO, USA
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Steele S, Taft-Benz S, Kawula T. A method for functional trans-complementation of intracellular Francisella tularensis. PLoS One 2014; 9:e88194. [PMID: 24505427 PMCID: PMC3913766 DOI: 10.1371/journal.pone.0088194] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Accepted: 01/04/2014] [Indexed: 12/24/2022] Open
Abstract
Francisella tularensis is a highly infectious bacterial pathogen that invades and replicates within numerous host cell types. After uptake, F. tularensis bacteria escape the phagosome, replicate within the cytosol, and suppress cytokine responses. However, the mechanisms employed by F. tularensis to thrive within host cells are mostly unknown. Potential F. tularensis mutants involved in host-pathogen interactions are typically discovered by negative selection screens for intracellular replication or virulence. Mutants that fulfill these criteria fall into two categories: mutants with intrinsic intracellular growth defects and mutants that fail to modify detrimental host cell processes. It is often difficult and time consuming to discriminate between these two possibilities. We devised a method to functionally trans-complement and thus identify mutants that fail to modify the host response. In this assay, host cells are consistently and reproducibly infected with two different F. tularensis strains by physically tethering the bacteria to antibody-coated beads. To examine the efficacy of this protocol, we tested phagosomal escape, cytokine suppression, and intracellular replication for F. tularensis ΔripA and ΔpdpC. ΔripA has an intracellular growth defect that is likely due to an intrinsic defect and fails to suppress IL-1β secretion. In the co-infection model, ΔripA was unable to replicate in the host cell when wild-type bacteria infected the same cell, but cytokine suppression was rescued. Therefore, ΔripA intracellular growth is due to an intrinsic bacterial defect while cytokine secretion results from a failed host-pathogen interaction. Likewise, ΔpdpC is deficient for phagosomal escape, intracellular survival and suppression of IL-1β secretion. Wild-type bacteria that entered through the same phagosome as ΔpdpC rescued all of these phenotypes, indicating that ΔpdpC failed to properly manipulate the host. In summary, functional trans-complementation using bead-bound bacteria co-infections is a method to rapidly identify mutants that fail to modify a host response. Francisella tularensis is a facultative intracellular bacterial pathogen and is the causative agent of the disease tularemia. F. tularensis enters host cells through phagocytosis, escapes the phagosome, and replicates in the host cell cytosol while suppressing cytokine secretion [1]–[4]. Although substantial progress has been made in understanding the intracellular life cycle of F. tularensis, the F. tularensis proteins responsible for manipulating many host cell pathways are unknown. Identifying novel host-pathogen effector proteins is difficult because there is no rapid method to reliably distinguish between bacterial proteins that modify host processes and proteins that are involved in bacterial processes that are required for the bacteria to survive or replicate in the intracellular environment. The ability to identify mutants that are deficient for host-pathogen interactions is important because it can aid in prioritizing the investigation of genes of interest and in downstream experimental design. Moreover, certain mutant phenotypes, such as decreased phagosomal escape, hinder investigation of other potential phenotypes. A method to specifically complement these phenotypes would allow for further characterizations of certain F. tularensis mutants. Thus we sought to develop a method to easily identify and functionally complement mutants that are deficient for interactions with the host.
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Affiliation(s)
- Shaun Steele
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, United States of America
| | - Sharon Taft-Benz
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, United States of America
| | - Thomas Kawula
- Department of Microbiology and Immunology, University of North Carolina at Chapel Hill, North Carolina, United States of America
- * E-mail:
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Bent ZW, Brazel DM, Tran-Gyamfi MB, Hamblin RY, VanderNoot VA, Branda SS. Use of a capture-based pathogen transcript enrichment strategy for RNA-Seq analysis of the Francisella tularensis LVS transcriptome during infection of murine macrophages. PLoS One 2013; 8:e77834. [PMID: 24155975 PMCID: PMC3796476 DOI: 10.1371/journal.pone.0077834] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Accepted: 09/09/2013] [Indexed: 12/17/2022] Open
Abstract
Francisella tularensis is a zoonotic intracellular pathogen that is capable of causing potentially fatal human infections. Like all successful bacterial pathogens, F. tularensis rapidly responds to changes in its environment during infection of host cells, and upon encountering different microenvironments within those cells. This ability to appropriately respond to the challenges of infection requires rapid and global shifts in gene expression patterns. In this study, we use a novel pathogen transcript enrichment strategy and whole transcriptome sequencing (RNA-Seq) to perform a detailed characterization of the rapid and global shifts in F. tularensis LVS gene expression during infection of murine macrophages. We performed differential gene expression analysis on all bacterial genes at two key stages of infection: phagosomal escape, and cytosolic replication. By comparing the F. tularensis transcriptome at these two stages of infection to that of the bacteria grown in culture, we were able to identify sets of genes that are differentially expressed over the course of infection. This analysis revealed the temporally dynamic expression of a number of known and putative transcriptional regulators and virulence factors, providing insight into their role during infection. In addition, we identified several F. tularensis genes that are significantly up-regulated during infection but had not been previously identified as virulence factors. These unknown genes may make attractive therapeutic or vaccine targets.
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Affiliation(s)
- Zachary W. Bent
- Sandia National Laboratories, Livermore, California, United States of America
- * E-mail:
| | - David M. Brazel
- Sandia National Laboratories, Livermore, California, United States of America
| | - Mary B. Tran-Gyamfi
- Sandia National Laboratories, Livermore, California, United States of America
| | - Rachelle Y. Hamblin
- Sandia National Laboratories, Livermore, California, United States of America
| | | | - Steven S. Branda
- Sandia National Laboratories, Livermore, California, United States of America
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Frederiksen RF, Paspaliari DK, Larsen T, Storgaard BG, Larsen MH, Ingmer H, Palcic MM, Leisner JJ. Bacterial chitinases and chitin-binding proteins as virulence factors. MICROBIOLOGY (READING, ENGLAND) 2013; 159:833-847. [PMID: 23519157 DOI: 10.1099/mic.0.051839-0] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Bacterial chitinases (EC 3.2.1.14) and chitin-binding proteins (CBPs) play a fundamental role in the degradation of the ubiquitous biopolymer chitin, and the degradation products serve as an important nutrient source for marine- and soil-dwelling bacteria. However, it has recently become clear that representatives of both Gram-positive and Gram-negative bacterial pathogens encode chitinases and CBPs that support infection of non-chitinous mammalian hosts. This review addresses this biological role of bacterial chitinases and CBPs in terms of substrate specificities, regulation, secretion and involvement in cellular and animal infection.
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Affiliation(s)
- Rikki F Frederiksen
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Dafni K Paspaliari
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Tanja Larsen
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Birgit G Storgaard
- Carlsberg Laboratory, Gamle Carlsbergvej 10, 1799 Copenhagen V., Denmark
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Marianne H Larsen
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Hanne Ingmer
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
| | - Monica M Palcic
- Carlsberg Laboratory, Gamle Carlsbergvej 10, 1799 Copenhagen V., Denmark
| | - Jørgen J Leisner
- Department of Veterinary Disease Biology, Faculty of Health Sciences, University of Copenhagen, Grønnegaardsvej 15, 1870 Frederiksberg C., Denmark
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Mahawar M, Atianand MK, Dotson RJ, Mora V, Rabadi SM, Metzger DW, Huntley JF, Harton JA, Malik M, Bakshi CS. Identification of a novel Francisella tularensis factor required for intramacrophage survival and subversion of innate immune response. J Biol Chem 2012; 287:25216-29. [PMID: 22654100 DOI: 10.1074/jbc.m112.367672] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Francisella tularensis, the causative agent of tularemia, is one of the deadliest agents of biological warfare and bioterrorism. Extremely high virulence of this bacterium is associated with its ability to dampen or subvert host innate immune response. The objectives of this study were to identify factors and understand the mechanisms of host innate immune evasion by F. tularensis. We identified and explored the pathogenic role of a mutant interrupted at gene locus FTL_0325, which encodes an OmpA-like protein. Our results establish a pathogenic role of FTL_0325 and its ortholog FTT0831c in the virulent F. tularensis SchuS4 strain in intramacrophage survival and suppression of proinflammatory cytokine responses. This study provides mechanistic evidence that the suppressive effects on innate immune responses are due specifically to these proteins and that FTL_0325 and FTT0831c mediate immune subversion by interfering with NF-κB signaling. Furthermore, FTT0831c inhibits NF-κB activity primarily by preventing the nuclear translocation of p65 subunit. Collectively, this study reports a novel F. tularensis factor that is required for innate immune subversion caused by this deadly bacterium.
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Affiliation(s)
- Manish Mahawar
- Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York 12208, USA
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Law HT, Lin AEJ, Kim Y, Quach B, Nano FE, Guttman JA. Francisella tularensis uses cholesterol and clathrin-based endocytic mechanisms to invade hepatocytes. Sci Rep 2011; 1:192. [PMID: 22355707 PMCID: PMC3240981 DOI: 10.1038/srep00192] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/28/2011] [Indexed: 12/16/2022] Open
Abstract
Francisella tularensis are highly infectious microbes that cause the disease tularemia. Although much of the bacterial burden is carried in non-phagocytic cells, the strategies these pathogens use to invade these cells remains elusive. To examine these mechanisms we developed two in vitro Francisella-based infection models that recapitulate the non-phagocytic cell infections seen in livers of infected mice. Using these models we found that Francisella novicida exploit clathrin and cholesterol dependent mechanisms to gain entry into hepatocytes. We also found that the clathrin accessory proteins AP-2 and Eps15 co-localized with invading Francisella novicida as well as the Francisella Live Vaccine Strain (LVS) during hepatocyte infections. Interestingly, caveolin, a protein involved in the invasion of Francisella in phagocytic cells, was not required for non-phagocytic cell infections. These results demonstrate a novel endocytic mechanism adopted by Francisella and highlight the divergence in strategies these pathogens utilize between non-phagocytic and phagocytic cell invasion.
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Affiliation(s)
- H T Law
- Simon Fraser University Department of Biological Sciences Shrum Science Centre Room B8276 Burnaby, BC, V5A 1S6
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KdgR, an IClR family transcriptional regulator, inhibits virulence mainly by repression of hrp genes in Xanthomonas oryzae pv. oryzae. J Bacteriol 2011; 193:6674-82. [PMID: 21984784 DOI: 10.1128/jb.05714-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
KdgR has been reported to negatively regulate the genes involved in degradation and metabolization of pectic acid and other extracellular enzymes in soft-rotting Erwinia spp. through direct binding to their promoters. The possible involvement of a KdgR orthologue in virulence by affecting the expression of extracellular enzymes in Xanthomonas oryzae pv. oryzae, the causal agent of rice blight disease, was examined by comparing virulence and regulation of extracellular enzymes between the wild type (WT) and a strain carrying a mutation in putative kdgR (ΔXoo0310 mutant). This putative kdgR mutant of X. oryzae pv. oryzae showed increased pathogenicity on rice without affecting the regulation of extracellular enzymes, such as amylase, cellulase, xylanase, and protease. However, the mutant carrying a mutation in an ortholog of xpsL, which encodes the functional secretion machinery for the extracellular enzymes, showed a dramatic decrease in pathogenicity on rice. Both mutants of kdgR and of xpsL orthologs showed higher expression of two major hrp regulatory genes, hrpG and hrpX, and the genes in the hrp operons when grown in hrp-inducing medium. Thus, both genes were shown to be involved in repression of hrp genes. The kdgR ortholog was thought to suppress virulence mainly by repressing the expression of hrp genes without affecting the expression of extracellular enzymes, unlike findings for the kdgR gene in soft-rotting Erwinia spp. On the other hand, xpsL was confirmed to be involved in virulence by promoting the secretion of extracellular enzymes in spite of repressing the expression of the hrp genes.
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Dai S, Mohapatra NP, Schlesinger LS, Gunn JS. Regulation of francisella tularensis virulence. Front Microbiol 2011; 1:144. [PMID: 21687801 PMCID: PMC3109300 DOI: 10.3389/fmicb.2010.00144] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2010] [Accepted: 12/21/2010] [Indexed: 12/29/2022] Open
Abstract
Francisella tularensis is one of the most virulent bacteria known and a Centers for Disease Control and Prevention Category A select agent. It is able to infect a variety of animals and insects and can persist in the environment, thus Francisella spp. must be able to survive in diverse environmental niches. However, F. tularensis has a surprising dearth of sensory and regulatory factors. Recent advancements in the field have identified new functions of encoded transcription factors and greatly expanded our understanding of virulence gene regulation. Here we review the current knowledge of environmental adaptation by F. tularensis, its transcriptional regulators and their relationship to animal virulence.
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Affiliation(s)
- Shipan Dai
- Center for Microbial Interface Biology, The Ohio State University Columbus, OH, USA
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