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Li J, Sayeed S, McClane BA. The presence of differentiated C2C12 muscle cells enhances toxin production and growth by Clostridium perfringens type A strain ATCC3624. Virulence 2024; 15:2388219. [PMID: 39192628 PMCID: PMC11364075 DOI: 10.1080/21505594.2024.2388219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2023] [Revised: 07/03/2024] [Accepted: 07/28/2024] [Indexed: 08/29/2024] Open
Abstract
Clostridium perfringens type A causes gas gangrene, which involves muscle infection. Both alpha toxin (PLC), encoded by the plc gene, and perfringolysin O (PFO), encoded by the pfoA gene, are important when type A strains cause gas gangrene in a mouse model. This study used the differentiated C2C12 muscle cell line to test the hypothesis that one or both of those toxins contributes to gas gangrene pathogenesis by releasing growth nutrients from muscle cells. RT-qPCR analyses showed that the presence of differentiated C2C12 cells induces C. perfringens type A strain ATCC3624 to upregulate plc and pfoA expression, as well as increase expression of several regulatory genes, including virS/R, agrB/D, and eutV/W. The VirS/R two component regulatory system (TCRS) and its coupled Agr-like quorum sensing system, along with the EutV/W TCRS (which regulates expression of genes involved in ethanolamine [EA] utilization), were shown to mediate the C2C12 cell-induced increase in plc and pfoA expression. EA was demonstrated to increase toxin gene expression. ATCC3624 growth increased in the presence of differentiated C2C12 muscle cells and this effect was shown to involve both PFO and PLC. Those membrane-active toxins were each cytotoxic for differentiated C2C12 cells, suggesting they support ATCC3624 growth by releasing nutrients from differentiated C2C12 cells. These findings support a model where, during gas gangrene, increased production of PFO and PLC in the presence of muscle cells causes more damage to those host cells, which release nutrients like EA that are then used to support C. perfringens growth in muscle.
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Affiliation(s)
- Jihong Li
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Sameera Sayeed
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
| | - Bruce A. McClane
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
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Jaramillo-Jaramillo AS, Coulson TJD, Hofacre C, Jones M, O'Neill L, Nguyen N, Labbe A. Effect of in-water administration of quorum system inhibitors in broilers' productive performance and intestinal microbiome in a mild necrotic enteritis challenge. Avian Pathol 2023; 52:309-322. [PMID: 37485826 DOI: 10.1080/03079457.2023.2224260] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 06/06/2023] [Accepted: 06/08/2023] [Indexed: 07/25/2023]
Abstract
The poultry industry has been facing the impact of necrotic enteritis (NE), a disease caused by the bacterium Clostridium perfringens producing the haemolytic toxin NetB. NE severity may vary from mild clinical to prominent enteric signs causing reduced growth rates and affecting feed conversion ratio. NetB production is controlled by the Agr-like quorum-sensing (QS) system, which coordinates virulence gene expression in response to bacterial cell density. In this study, the peptide-containing cell-free spent media (CFSM) from Enterococcus faecium was tested in NE challenged broilers in two battery cage and one floor pen studies. Results showed a significant reduction of NE mortality. Metagenomic sequencing of the jejunum microbiome revealed no impact of the CFSM on the microbial community, and growth of C. perfringens was unaffected by CFSM in vitro. The expression of QS-controlled virulence genes netB, plc and pfoA was found to be significantly repressed by CFSM during the mid-logarithmic stage of C. perfringens growth and this corresponded with a significant decrease in haemolytic activity. Purified fractions of CFSM containing bioactive peptides were found to cause reduced haemolysis. These results showed that bioactive peptides reduce NE mortality in broilers by interfering with the QS system of C. perfringens and reducing bacterial virulence. Furthermore, the microbiome of C. perfringens-challenged broilers is not affected by quorum sensing inhibitor containing CFSM.
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Affiliation(s)
| | | | - C Hofacre
- Southern Poultry Research Group, Inc., Watkinsville, GA, USA
| | - M Jones
- Southern Poultry Research Group, Inc., Watkinsville, GA, USA
| | - L O'Neill
- MicroSintesis Inc., Victoria, P.E.I. Canada
| | - N Nguyen
- MicroSintesis Inc., Victoria, P.E.I. Canada
| | - A Labbe
- MicroSintesis Inc., Victoria, P.E.I. Canada
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3
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Edwards AN, McBride SM. The RgaS-RgaR two-component system promotes Clostridioides difficile sporulation through a small RNA and the Agr1 system. PLoS Genet 2023; 19:e1010841. [PMID: 37844084 PMCID: PMC10602386 DOI: 10.1371/journal.pgen.1010841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2023] [Revised: 10/26/2023] [Accepted: 10/02/2023] [Indexed: 10/18/2023] Open
Abstract
The ability to form a dormant spore is essential for the survival of the anaerobic pathogen, Clostridioides difficile, outside of the mammalian gastrointestinal tract. The initiation of sporulation is governed by the master regulator of sporulation, Spo0A, which is activated by phosphorylation. Multiple sporulation factors control Spo0A phosphorylation; however, this regulatory pathway is not well defined in C. difficile. We discovered that RgaS and RgaR, a conserved orphan histidine kinase and orphan response regulator, function together as a cognate two-component regulatory system to directly activate transcription of several genes. One of these targets, agrB1D1, encodes gene products that synthesize and export a small quorum-sensing peptide, AgrD1, which positively influences expression of early sporulation genes. Another target, a small regulatory RNA now known as SpoZ, impacts later stages of sporulation through a small hypothetical protein and an additional, unknown regulatory mechanism(s). Unlike Agr systems in many organisms, AgrD1 does not activate the RgaS-RgaR two-component system, and thus, is not responsible for autoregulating its own production. Altogether, we demonstrate that C. difficile utilizes a conserved two-component system that is uncoupled from quorum-sensing to promote sporulation through two distinct regulatory pathways.
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Affiliation(s)
- Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, Georgia, United States of America
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Alenezi T, Fu Y, Alrubaye B, Alanazi T, Almansour A, Wang H, Sun X. Potent Bile Acid Microbial Metabolites Modulate Clostridium perfringens Virulence. Pathogens 2023; 12:1202. [PMID: 37887718 PMCID: PMC10610205 DOI: 10.3390/pathogens12101202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2023] [Revised: 09/19/2023] [Accepted: 09/26/2023] [Indexed: 10/28/2023] Open
Abstract
Clostridium perfringens is a versatile pathogen, inducing diseases in the skin, intestine (such as chicken necrotic enteritis (NE)), and other organs. The classical sign of NE is the foul smell gas in the ballooned small intestine. We hypothesized that deoxycholic acid (DCA) reduced NE by inhibiting C. perfringens virulence signaling pathways. To evaluate the hypothesis, C. perfringens strains CP1 and wild-type (WT) HN13 and its mutants were cultured with different bile acids, including DCA and isoallolithocholic acid (isoalloLCA). Growth, hydrogen sulfide (H2S) production, and virulence gene expression were measured. Notably, isoalloLCA was more potent in reducing growth, H2S production, and virulence gene expression in CP1 and WT HN13 compared to DCA, while other bile acids were less potent compared to DCA. Interestingly, there was a slightly different impact between DCA and isoalloLCA on the growth, H2S production, and virulence gene expression in the three HN13 mutants, suggesting possibly different signaling pathways modulated by the two bile acids. In conclusion, DCA and isoalloLCA reduced C. perfringens virulence by transcriptionally modulating the pathogen signaling pathways. The findings could be used to design new strategies to prevent and treat C. perfringens-induced diseases.
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Affiliation(s)
- Tahrir Alenezi
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
- Cell and Molecular Biology, University of Arkansas, Fayetteville, AR 72701, USA
- College of Medical Applied Sciences, The Northern Border University, Arar 91431, Saudi Arabia
| | - Ying Fu
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
| | - Bilal Alrubaye
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
| | - Thamer Alanazi
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
- Cell and Molecular Biology, University of Arkansas, Fayetteville, AR 72701, USA
| | - Ayidh Almansour
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
- Cell and Molecular Biology, University of Arkansas, Fayetteville, AR 72701, USA
| | - Hong Wang
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
- Cell and Molecular Biology, University of Arkansas, Fayetteville, AR 72701, USA
| | - Xiaolun Sun
- Center of Excellence for Poultry Science, University of Arkansas, Fayetteville, AR 72701, USA; (T.A.); (Y.F.); (B.A.); (T.A.); (A.A.); (H.W.)
- Cell and Molecular Biology, University of Arkansas, Fayetteville, AR 72701, USA
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5
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Edwards AN, McBride SM. The RgaS-RgaR two-component system promotes Clostridioides difficile sporulation through a small RNA and the Agr1 system. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.26.546640. [PMID: 37425791 PMCID: PMC10327067 DOI: 10.1101/2023.06.26.546640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
The ability to form a dormant spore is essential for the survival of the anaerobic, gastrointestinal pathogen Clostridioides difficile outside of the mammalian gastrointestinal tract. The initiation of sporulation is governed by the master regulator of sporulation, Spo0A, which is activated by phosphorylation. Multiple sporulation factors control Spo0A phosphorylation; however, this regulatory pathway is not well defined in C. difficile. We discovered that RgaS and RgaR, a conserved orphan histidine kinase and orphan response regulator, function together as a cognate two-component regulatory system to directly activate transcription of several genes. One of these targets, agrB1D1, encodes gene products that synthesize and export a small quorum-sensing peptide, AgrD1, which positively influences expression of early sporulation genes. Another target, a small regulatory RNA now known as SrsR, impacts later stages of sporulation through an unknown regulatory mechanism(s). Unlike Agr systems in many organisms, AgrD1 does not activate the RgaS-RgaR two-component system, and thus, is not responsible for autoregulating its own production. Altogether, we demonstrate that C. difficile utilizes a conserved two-component system that is uncoupled from quorum-sensing to promote sporulation through two distinct regulatory pathways.
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Affiliation(s)
- Adrianne N. Edwards
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
| | - Shonna M. McBride
- Department of Microbiology and Immunology, Emory University School of Medicine, Emory Antibiotic Resistance Center, Atlanta, GA, USA
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Identifying the Basis for VirS/VirR Two-Component Regulatory System Control of Clostridium perfringens Beta-Toxin Production. J Bacteriol 2021; 203:e0027921. [PMID: 34228498 DOI: 10.1128/jb.00279-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium perfringens toxin production is often regulated by the Agr-like quorum sensing (QS) system signaling the VirS/VirR two-component regulatory system (TCRS), which consists of the VirS membrane sensor histidine kinase and the VirR response regulator. VirS/VirR is known to directly control expression of some genes by binding to a DNA binding motif consisting of two VirR boxes located within 500 bp of the target gene start codon. Alternatively, the VirS/VirR system can indirectly regulate production levels of other proteins by increasing expression of a small regulatory RNA, VR-RNA. Previous studies demonstrated that C. perfringens beta-toxin (CPB) production by C. perfringens type B and C strains is positively regulated by both the Agr-like QS and the VirS/VirR TCRS, but the mechanism has been unclear. The current study first inactivated the vrr gene encoding VR-RNA to show that VirS/VirR regulation of cpb expression does not involve VR-RNA. Subsequently, bioinformatic analyses identified a potential VirR binding motif, along with a predicted strong promoter, ∼1.4 kb upstream of the cpb open reading frame (ORF). Two insertion sequences were present between this VirR binding motif/promoter region and the cpb ORF. PCR screening of a collection of strains carrying cpb showed that the presence and sequence of this VirR binding motif/promoter is highly conserved among CPB-producing strains. Reverse transcription-PCR (RT-PCR) and a GusA reporter assay showed this VirR binding motif is important for regulating CPB production. These findings indicate that VirS/VirR directly regulates cpb expression via VirS binding to a VirR binding motif located unusually distant from the cpb start codon. IMPORTANCE Clostridium perfringens beta-toxin (CPB) is only produced by type B and C strains. Production of CPB is essential for the pathogenesis of type C-associated infections, which include hemorrhagic necrotizing enteritis and enterotoxemia in both humans and animals. In addition, CPB can synergize with other toxins during C. perfringens gastrointestinal diseases. CPB toxin production is cooperatively regulated by the Agr-like quorum sensing (QS) system and the VirS/VirR two-component regulatory system. This study now reports that the VirS/VirR regulatory cascade directly controls expression of the cpb gene via a process involving a VirR box binding motif located unusually far (∼1.4 kb) upstream of the cpb ORF. This study provides a better understanding of the regulatory mechanisms for CPB production by the VirS/VirR regulatory cascade.
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A Novel PilR/PilS Two-Component System Regulates Necrotic Enteritis Pilus Production in Clostridium perfringens. J Bacteriol 2021; 203:e0009621. [PMID: 34152200 DOI: 10.1128/jb.00096-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium perfringens causes necrotic enteritis (NE) in poultry. A chromosomal locus (VR-10B) was previously identified in NE-causing C. perfringens strains that encodes an adhesive pilus (NE pilus), along with a two-component system (TCS) designated here as PilRS. While the NE pilus is important in pathogenesis, the role of PilRS remains to be determined. The current study investigated the function of PilRS, as well as the Agr-like quorum-sensing (QS) system and VirSR TCS in the regulation of pilin production. Isogenic pilR, agrB, and virR null mutants were generated from the parent strain CP1 by insertional inactivation using the ClosTron system, along with the respective complemented strains. Immunoblotting analyses showed no detectable pilus production in the CP1pilR mutant, while production in its complement (CP1pilR+) was greater than wild-type levels. In contrast, pilus production in the agrB and virR mutants was comparable or higher than the wild type but reduced in their respective complemented strains. When examined for collagen-binding activity, the pilR mutant showed significantly lower binding to most collagen types (types I to V) than parental CP1 (P ≤ 0.05), whereas this activity was restored in the complemented strain (P > 0.05). In contrast, binding of agrB and virR mutants to collagen showed no significant differences in collagen-binding activity compared to CP1 (P > 0.05), whereas the complemented strains exhibited significantly reduced binding (P ≤ 0.05). These data suggest the PilRS TCS positively regulates pilus production in C. perfringens, while the Agr-like QS system may serve as a negative regulator of this operon. IMPORTANCE Clostridium perfringens type G isolates cause necrotic enteritis (NE) in poultry, presenting a major challenge for poultry production in the postantibiotic era. Multiple factors in C. perfringens, including both virulent and nonvirulent, are involved in the development of the disease. We previously discovered a cluster of C. perfringens genes that encode a pilus involved in adherence and NE development, along with a predicted two-component regulatory system (TCS), designated PilRS. In the present study, we have demonstrated the role of PilRS in regulating pilus production and collagen binding of C. perfringens. In addition, the Agr-like quorum sensing signaling pathway was found to be involved in the regulation. These findings have identified additional targets for developing nonantibiotic strategies to control NE disease.
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Identification of a non-coding RNA and its putative involvement in the regulation of tetanus toxin synthesis in Clostridium tetani. Sci Rep 2021; 11:4157. [PMID: 33603121 PMCID: PMC7892561 DOI: 10.1038/s41598-021-83623-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 01/29/2021] [Indexed: 11/17/2022] Open
Abstract
Clostridium tetani produces the tetanus toxin (TeNT), one of the most powerful bacterial toxins known to humankind and responsible for tetanus. The regulation of toxin expression is complex and involves the alternative sigma factor TetR as well as other regulators. Here, a transcriptional analysis of the TeNT-encoding large plasmid of C. tetani identified a putative non-coding small RNA (sRNA), located in close vicinity of the 3′ untranslated region of the tent gene. A northern blot experiment could identify a respective sRNA with a size of approx. 140 nucleotides. Sequence analysis showed that the sRNA contains a 14-nucleotide region that is complementary to a 5′ located region of tent. In order to investigate the function of the sRNA, we applied a RNA interference approach targeting the sRNA in two C. tetani wild-type strains; the constructed antisense C. tetani strains showed an approx. threefold increase in both extracellular and total TeNT production compared to the respective wild-type strains. In addition, recombinant C. tetani strains were constructed that contained tent-locus harboring plasmids with and without the sRNA. However, the introduction of the tent-locus without the sRNA in a C. tetani strain lacking the wild-type TeNT-encoding large plasmid resulted in a lower TeNT production compared to the same strain with recombinant tent-locus with the sRNA. This suggests that the expression or the effect of the sRNA is modulated by the C. tetani genetic background, notably that of the wild-type TeNT-encoding large plasmid. In addition, some recombinant strains exhibited modulated growth patterns, characterized by premature bacterial cell lysis. Taken together, our data indicate that the sRNA acts as a negative regulator of TeNT synthesis, with a possible impact on the growth of C. tetani. We hypothesize that the role of this sRNA is to limit toxin levels in the exponential growth phase in order to prevent premature bacterial lysis.
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Piattelli E, Peltier J, Soutourina O. Interplay between Regulatory RNAs and Signal Transduction Systems during Bacterial Infection. Genes (Basel) 2020; 11:E1209. [PMID: 33081172 PMCID: PMC7602753 DOI: 10.3390/genes11101209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 10/08/2020] [Accepted: 10/13/2020] [Indexed: 12/13/2022] Open
Abstract
The ability of pathogenic bacteria to stably infect the host depends on their capacity to respond and adapt to the host environment and on the efficiency of their defensive mechanisms. Bacterial envelope provides a physical barrier protecting against environmental threats. It also constitutes an important sensory interface where numerous sensing systems are located. Signal transduction systems include Two-Component Systems (TCSs) and alternative sigma factors. These systems are able to sense and respond to the ever-changing environment inside the host, altering the bacterial transcriptome to mitigate the impact of the stress. The regulatory networks associated with signal transduction systems comprise small regulatory RNAs (sRNAs) that can be directly involved in the expression of virulence factors. The aim of this review is to describe the importance of TCS- and alternative sigma factor-associated sRNAs in human pathogens during infection. The currently available genome-wide approaches for studies of TCS-regulated sRNAs will be discussed. The differences in the signal transduction mediated by TCSs between bacteria and higher eukaryotes and the specificity of regulatory RNAs for their targets make them appealing targets for discovery of new strategies to fight against multi-resistant bacteria.
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Affiliation(s)
- Emma Piattelli
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris-Saclay, 91198 Gif-sur-Yvette, France; (E.P.); (J.P.)
| | - Johann Peltier
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris-Saclay, 91198 Gif-sur-Yvette, France; (E.P.); (J.P.)
- Laboratoire Pathogenèses des Bactéries Anaérobies, Institut Pasteur, UMR CNRS 2001, Université de Paris, 75015 Paris, France
| | - Olga Soutourina
- Institute for Integrative Biology of the Cell (I2BC), CNRS, CEA, Université Paris-Saclay, 91198 Gif-sur-Yvette, France; (E.P.); (J.P.)
- Institut Universitaire de France, CEDEX 05, 75231 Paris, France
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11
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Zheng C, Li L, Ge H, Meng H, Li Y, Bei W, Zhou X. Role of two-component regulatory systems in the virulence of Streptococcus suis. Microbiol Res 2018; 214:123-128. [PMID: 30031474 DOI: 10.1016/j.micres.2018.07.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 06/19/2018] [Accepted: 07/07/2018] [Indexed: 01/01/2023]
Abstract
Streptococcus suis is an important zoonotic pathogen that causes severe infections and great economic losses worldwide. Understanding how this pathogen senses and responds to environmental signals during the infectious process can offer insight into its pathogenesis and may be helpful in the development of drug targets. Two-component regulatory systems (TCSs) play an essential role in this environmental response. In S. suis, at least 15 groups of TCSs have been predicted. Among them, several have been demonstrated to be involved in virulence and/or stress response. In this review, we discuss the progress in the study of TCSs in S. suis, focusing on the role of these systems in the virulence of this bacterium.
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Affiliation(s)
- Chengkun Zheng
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China; State Key Laboratory of Agricultural Microbiology/The Cooperative Innovation Center for Sustainable Pig Production, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China
| | - Lingzhi Li
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Haojie Ge
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Hongmei Meng
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Yang Li
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China
| | - Weicheng Bei
- State Key Laboratory of Agricultural Microbiology/The Cooperative Innovation Center for Sustainable Pig Production, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, 430070, China.
| | - Xiaohui Zhou
- Jiangsu Key Laboratory of Zoonosis/Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, 225009, China; Joint International Research Laboratory of Agriculture and Agri-Product Safety/Key Laboratory of Prevention and Control of Biological Hazard Factors (Animal Origin) for Agrifood Safety and Quality, The Ministry of Education of China, Yangzhou University, Yangzhou, 225009, China; Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, CT, 06269, USA.
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12
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Adachi K, Ohtani K, Kawano M, Singh RP, Yousuf B, Sonomoto K, Shimizu T, Nakayama J. Metabolic dependent and independent pH-drop shuts down VirSR quorum sensing in Clostridium perfringens. J Biosci Bioeng 2018; 125:525-531. [PMID: 29373309 DOI: 10.1016/j.jbiosc.2017.12.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Revised: 12/20/2017] [Accepted: 12/20/2017] [Indexed: 12/20/2022]
Abstract
Clostridium perfringens produces various exotoxins and enzymes that cause food poisoning and gas gangrene. The genes involved in virulence are regulated by the agr-like quorum sensing (QS) system, which consists of a QS signal synthesis system and a VirSR two-component regulatory system (VirSR TCS) which is a global regulatory system composed of signal sensor kinase (VirS) and response regulator (VirR). We found that the perfringolysin O gene (pfoA) was transiently expressed during mid-log phase of bacterial growth; its expression was rapidly shut down thereafter, suggesting the existence of a self-quorum quenching (sQQ) system. The sQQ system was induced by the addition of stationary phase culture supernatant (SPCS). Activity of the sQQ system was heat stable, and was present following filtration through the ultrafiltration membrane, suggesting that small molecules acted as sQQ agents. In addition, sQQ was also induced by pure acetic and butyric acids at concentrations equivalent to those in the stationary phase culture, suggesting that organic acids produced by C. perfringens were involved in sQQ. In pH-controlled batch culture, sQQ was greatly diminished; expression level of pfoA extended to late-log growth phase, and was eventually increased by one order of magnitude. Furthermore, hydrochloric acid induced sQQ at the same pH as was used in organic acids. SPCS also suppressed the expression of genes regulated by VirSR TCS. Overall, the expression of virulence factors of C. perfringens was downregulated by the sQQ system, which was mediated by primary acidic metabolites and acidic environments. This suggested the possibility of pH-controlled anti-virulence strategies.
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Affiliation(s)
- Keika Adachi
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan
| | - Kaori Ohtani
- Department of Bacteriology, Graduate School of Medical Science, University of Kanazawa, 13-1 Takaramachi, Kanazawa, Ishikawa 920-8203, Japan; Miyarisan Pharmaceutical Co. Ltd., 1-10-3 Kaminakazato, Kita-ku, Tokyo 114-0016, Japan
| | - Michio Kawano
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan
| | - Ravindra Pal Singh
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan
| | - Basit Yousuf
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan
| | - Kenji Sonomoto
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan
| | - Tohru Shimizu
- Department of Bacteriology, Graduate School of Medical Science, University of Kanazawa, 13-1 Takaramachi, Kanazawa, Ishikawa 920-8203, Japan
| | - Jiro Nakayama
- Laboratory of Microbial Technology, Faculty of Agriculture, Graduate School, Kyushu University, Fukuoka 812-8581, Japan.
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Effect of Trehalose and Trehalose Transport on the Tolerance of Clostridium perfringens to Environmental Stress in a Wild Type Strain and Its Fluoroquinolone-Resistant Mutant. Int J Microbiol 2017; 2016:4829716. [PMID: 28058047 PMCID: PMC5183799 DOI: 10.1155/2016/4829716] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 10/10/2016] [Indexed: 11/17/2022] Open
Abstract
Trehalose has been shown to protect bacterial cells from environmental stress. Its uptake and osmoprotective effect in Clostridium perfringens were investigated by comparing wild type C. perfringens ATCC 13124 with a fluoroquinolone- (gatifloxacin-) resistant mutant. In a chemically defined medium, trehalose and sucrose supported the growth of the wild type but not that of the mutant. Microarray data and qRT-PCR showed that putative genes for the phosphorylation and transport of sucrose and trehalose (via phosphoenolpyruvate-dependent phosphotransferase systems, PTS) and some regulatory genes were downregulated in the mutant. The wild type had greater tolerance than the mutant to salts and low pH; trehalose and sucrose further enhanced the osmotolerance of the wild type to NaCl. Expression of the trehalose-specific PTS was lower in the fluoroquinolone-resistant mutant. Protection of C. perfringens from environmental stress could therefore be correlated with the ability to take up trehalose.
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14
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Gene regulation by the VirS/VirR system in Clostridium perfringens. Anaerobe 2016; 41:5-9. [DOI: 10.1016/j.anaerobe.2016.06.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Revised: 06/07/2016] [Accepted: 06/07/2016] [Indexed: 12/21/2022]
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15
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Regulation of Toxin Production in Clostridium perfringens. Toxins (Basel) 2016; 8:toxins8070207. [PMID: 27399773 PMCID: PMC4963840 DOI: 10.3390/toxins8070207] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2016] [Accepted: 06/24/2016] [Indexed: 01/10/2023] Open
Abstract
The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here.
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16
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Low LY, Harrison PF, Lin YH, Boyce JD, Rood JI, Cheung JK. RNA-seq analysis of virR and revR mutants of Clostridium perfringens. BMC Genomics 2016; 17:391. [PMID: 27216822 PMCID: PMC4877802 DOI: 10.1186/s12864-016-2706-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Accepted: 05/05/2016] [Indexed: 12/15/2022] Open
Abstract
Background Clostridium perfringens causes toxin-mediated diseases, including gas gangrene (clostridial myonecrosis) and food poisoning in humans. The production of the toxins implicated in gas gangrene, α-toxin and perfringolysin O, is regulated by the VirSR two-component regulatory system. In addition, RevR, an orphan response regulator, has been shown to affect virulence in the mouse myonecrosis model. RevR positively regulates the expression of genes that encode hydrolytic enzymes, including hyaluronidases and sialidases. Results To further characterize the VirSR and RevR regulatory networks, comparative transcriptomic analysis was carried out with strand-specific RNA-seq on C. perfringens strain JIR325 and its isogenic virR and revR regulatory mutants. Using the edgeR analysis package, 206 genes in the virR mutant and 67 genes in the revR mutant were found to be differentially expressed. Comparative analysis revealed that VirR acts as a global negative regulator, whilst RevR acts as a global positive regulator. Therefore, about 95 % of the differentially expressed genes were up-regulated in the virR mutant, whereas 81 % of the differentially expressed genes were down-regulated in the revR mutant. Importantly, we identified 23 genes that were regulated by both VirR and RevR, 18 of these genes, which included the sporulation-specific spoIVA, sigG and sigF genes, were regulated positively and negatively by RevR and VirR, respectively. Furthermore, analysis of the mapped RNA-seq reads visualized as depth of coverage plots showed that there were 93 previously unannotated transcripts in intergenic regions. These transcripts potentially encode small RNA molecules. Conclusion In conclusion, using strand-specific RNA-seq analysis, this study has identified differentially expressed chromosomal and pCP13 native plasmid-encoded genes, antisense transcripts, and transcripts within intergenic regions that are controlled by the VirSR or RevR regulatory systems. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2706-2) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Lee-Yean Low
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, 3800, Australia
| | - Paul F Harrison
- Monash Bioinformatics Platform, Monash University, Clayton, 3800, Australia
| | - Ya-Hsun Lin
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, 3800, Australia
| | - John D Boyce
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, 3800, Australia
| | - Julian I Rood
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, 3800, Australia
| | - Jackie K Cheung
- Infection and Immunity Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, 3800, Australia.
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17
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André G, Haudecoeur E, Courtois E, Monot M, Dupuy B, Rodionov DA, Martin-Verstraete I. Cpe1786/IscR of Clostridium perfringens represses expression of genes involved in Fe-S cluster biogenesis. Res Microbiol 2016; 168:345-355. [PMID: 27020244 DOI: 10.1016/j.resmic.2016.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 03/14/2016] [Accepted: 03/16/2016] [Indexed: 12/27/2022]
Abstract
Cpe1786 of Clostridium perfringens is an Rrf2-type regulator containing the three-cysteine residues coordinating a Fe-S in IscR, the repressor controlling Fe-S homeostasis in enterobacteria. The cpe1786 gene formed an operon with iscSU involved in Fe-S biogenesis and tmrU. This operon was transcribed from a σA-dependent promoter. We showed that in the heterologous host Bacillus subtilis, Cpe1786, renamed IscRCp, negatively controlled its own transcription. We constructed an iscR mutant in C. perfringens. We then compared the expression profile of strain 13 and of the iscR mutant. IscRCp controlled expression of genes involved in Fe-S biogenesis, in amino acid or sugar metabolisms, in fermentation pathways and in host compound utilization. We then demonstrated, using a ChIP-PCR experiment, that IscRCp interacted with its promoter region in vivo in C. perfringens and with the promoter of cpe2093 encoding an amino acid ABC transporter. We utilized a comparative genomic approach to infer a candidate IscR binding motif and reconstruct IscR regulons in clostridia. We showed that point mutations in the conserved motif of 29 bp identified upstream of iscR decreased the cysteine-dependent repression of iscR mediated by IscRCp.
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Affiliation(s)
- Gaelle André
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Elise Haudecoeur
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Emmanuelle Courtois
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Marc Monot
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Bruno Dupuy
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France
| | - Dmitry A Rodionov
- Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow 127994, Russia
| | - Isabelle Martin-Verstraete
- Institut Pasteur, Laboratoire de Pathogénèse des Bactéries anaérobies, 28 rue du Docteur Roux, 75015 Paris, France; Université Paris 7-Denis Diderot, Sorbonne Paris Cité, 75205 Paris, France.
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18
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The Mechanisms of Virulence Regulation by Small Noncoding RNAs in Low GC Gram-Positive Pathogens. Int J Mol Sci 2015; 16:29797-814. [PMID: 26694351 PMCID: PMC4691137 DOI: 10.3390/ijms161226194] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Revised: 12/01/2015] [Accepted: 12/04/2015] [Indexed: 11/30/2022] Open
Abstract
The discovery of small noncoding regulatory RNAs (sRNAs) in bacteria has grown tremendously recently, giving new insights into gene regulation. The implementation of computational analysis and RNA sequencing has provided new tools to discover and analyze potential sRNAs. Small regulatory RNAs that act by base-pairing to target mRNAs have been found to be ubiquitous and are the most abundant class of post-transcriptional regulators in bacteria. The majority of sRNA studies has been limited to E. coli and other gram-negative bacteria. However, examples of sRNAs in gram-positive bacteria are still plentiful although the detailed gene regulation mechanisms behind them are not as well understood. Strict virulence control is critical for a pathogen’s survival and many sRNAs have been found to be involved in that process. This review outlines the targets and currently known mechanisms of trans-acting sRNAs involved in virulence regulation in various gram-positive pathogens. In addition, their shared characteristics such as CU interaction motifs, the role of Hfq, and involvement in two-component regulators, riboswitches, quorum sensing, or toxin/antitoxin systems are described.
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19
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Yasugi M, Sugahara Y, Hoshi H, Kondo K, Talukdar PK, Sarker MR, Yamamoto S, Kamata Y, Miyake M. In vitro cytotoxicity induced by Clostridium perfringens isolate carrying a chromosomal cpe gene is exclusively dependent on sporulation and enterotoxin production. Microb Pathog 2015; 85:1-10. [DOI: 10.1016/j.micpath.2015.04.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 04/07/2015] [Accepted: 04/21/2015] [Indexed: 12/31/2022]
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20
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Desouky SE, Shojima A, Singh RP, Matsufuji T, Igarashi Y, Suzuki T, Yamagaki T, Okubo KI, Ohtani K, Sonomoto K, Nakayama J. Cyclodepsipeptides produced by actinomycetes inhibit cyclic-peptide-mediated quorum sensing in Gram-positive bacteria. FEMS Microbiol Lett 2015; 362:fnv109. [PMID: 26149266 DOI: 10.1093/femsle/fnv109] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2015] [Indexed: 12/18/2022] Open
Abstract
Cyclic peptides are commonly used as quorum-sensing autoinducers in Gram-positive Firmicutes bacteria. Well-studied examples of such molecules are thiolactone and lactone, used to regulate the expression of a series of virulence genes in the agr system of Staphylococcus aureus and the fsr system of Enterococcus faecalis, respectively. Three cyclodepsipeptides WS9326A, WS9326B and cochinmicin II/III were identified as a result of screening actinomycetes culture extracts for activity against the agr/fsr system. These molecules are already known as receptor antagonists, the first two for tachykinin and the last one for endothelin. WS9326A also inhibited the transcription of pfoA regulated by the VirSR two-component system in Clostridium perfringens. Receptor-binding assays using a fluorescence-labeled autoinducer (FITC-GBAP) showed that WS9326A and WS9326B act as receptor antagonists in this system. In addition, an ex vivo assay showed that WS9326B substantially attenuated the toxicity of S. aureus for human corneal epithelial cells. These results suggest that these three natural cyclodepsipeptides have therapeutic potential for targeting the cyclic peptide-mediated quorum sensing of Gram-positive pathogens.
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Affiliation(s)
- Said E Desouky
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan Department of Botany and Microbiology, Faculty of Science, Al-azhar University, 11884 Nasr, Cairo, Egypt
| | - Akane Shojima
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Ravindra Pal Singh
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Takahisa Matsufuji
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Yasuhiro Igarashi
- Biotechnology Research Center, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
| | - Takashi Suzuki
- Department of Ophthalmology, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan
| | - Tohru Yamagaki
- Suntory Foundation for Life Sciences, Bioorganic Research Institute, 1-1-1 Wakayamadai, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan
| | - Ken-Ichi Okubo
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Kaori Ohtani
- Department of Bacteriology, University of Kanazawa, 13-1 Takaramachi, Kanazawa, Ishikawa 920-8203, Japan
| | - Kenji Sonomoto
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
| | - Jiro Nakayama
- Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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21
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Perfringolysin O: The Underrated Clostridium perfringens Toxin? Toxins (Basel) 2015; 7:1702-21. [PMID: 26008232 PMCID: PMC4448169 DOI: 10.3390/toxins7051702] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Accepted: 05/08/2015] [Indexed: 12/21/2022] Open
Abstract
The anaerobic bacterium Clostridium perfringens expresses multiple toxins that promote disease development in both humans and animals. One such toxin is perfringolysin O (PFO, classically referred to as θ toxin), a pore-forming cholesterol-dependent cytolysin (CDC). PFO is secreted as a water-soluble monomer that recognizes and binds membranes via cholesterol. Membrane-bound monomers undergo structural changes that culminate in the formation of an oligomerized prepore complex on the membrane surface. The prepore then undergoes conversion into the bilayer-spanning pore measuring approximately 250–300 Å in diameter. PFO is expressed in nearly all identified C. perfringens strains and harbors interesting traits that suggest a potential undefined role for PFO in disease development. Research has demonstrated a role for PFO in gas gangrene progression and bovine necrohemorrhagic enteritis, but there is limited data available to determine if PFO also functions in additional disease presentations caused by C. perfringens. This review summarizes the known structural and functional characteristics of PFO, while highlighting recent insights into the potential contributions of PFO to disease pathogenesis.
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22
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Ohtani K, Shimizu T. Regulation of toxin gene expression in Clostridium perfringens. Res Microbiol 2015; 166:280-9. [DOI: 10.1016/j.resmic.2014.09.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 11/16/2022]
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23
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Papenfort K, Vanderpool CK. Target activation by regulatory RNAs in bacteria. FEMS Microbiol Rev 2015; 39:362-78. [PMID: 25934124 DOI: 10.1093/femsre/fuv016] [Citation(s) in RCA: 160] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2015] [Indexed: 12/15/2022] Open
Abstract
Bacterial small regulatory RNAs (sRNAs) are commonly known to repress gene expression by base pairing to target mRNAs. In many cases, sRNAs base pair with and sequester mRNA ribosome-binding sites, resulting in translational repression and accelerated transcript decay. In contrast, a growing number of examples of translational activation and mRNA stabilization by sRNAs have now been documented. A given sRNA often employs a conserved region to interact with and regulate both repressed and activated targets. However, the mechanisms underlying activation differ substantially from repression. Base pairing resulting in target activation can involve sRNA interactions with the 5(') untranslated region (UTR), the coding sequence or the 3(') UTR of the target mRNAs. Frequently, the activities of protein factors such as cellular ribonucleases and the RNA chaperone Hfq are required for activation. Bacterial sRNAs, including those that function as activators, frequently control stress response pathways or virulence-associated functions required for immediate responses to changing environments. This review aims to summarize recent advances in knowledge regarding target mRNA activation by bacterial sRNAs, highlighting the molecular mechanisms and biological relevance of regulation.
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Affiliation(s)
- Kai Papenfort
- Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA Department of Biology I, Ludwig-Maximilians-University Munich, 82152 Martinsried, Germany
| | - Carin K Vanderpool
- Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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24
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25
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Abstract
Small regulatory RNAs (sRNAs) that act by base-pairing were first discovered in so-called accessory DNA elements—plasmids, phages, and transposons—where they control replication, maintenance, and transposition. Since 2001, a huge body of work has been performed to predict and identify sRNAs in a multitude of bacterial genomes. The majority of chromosome-encoded sRNAs have been investigated in E. coli and other Gram-negative bacteria. However, during the past five years an increasing number of sRNAs were found in Gram-positive bacteria. Here, we outline our current knowledge on chromosome-encoded sRNAs from low-GC Gram-positive species that act by base-pairing, i.e., an antisense mechanism. We will focus on sRNAs with known targets and defined regulatory mechanisms with special emphasis on Bacillus subtilis.
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Affiliation(s)
- Sabine Brantl
- Friedrich-Schiller-Universität Jena; Biologisch-Pharmazeutische Fakultät; AG Bakteriengenetik; Philosophenweg 12; Jena, Germany
| | - Reinhold Brückner
- Mikrobiologie; TU Kaiserslautern; Paul-Ehrlich-Str. 23; D-67663 Kaiserslautern, Germany
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26
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Chen J, Ma M, Uzal FA, McClane BA. Host cell-induced signaling causes Clostridium perfringens to upregulate production of toxins important for intestinal infections. Gut Microbes 2014; 5:96-107. [PMID: 24061146 PMCID: PMC4049945 DOI: 10.4161/gmic.26419] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Clostridium perfringens causes enteritis and enterotoxemia in humans and livestock due to prolific toxin production. In broth culture, C. perfringens uses the Agr-like quorum sensing (QS) system to regulate production of toxins important for enteritis/enterotoxemia, including beta toxin (CPB), enterotoxin, and epsilon toxin (ETX). The VirS/VirR two-component regulatory system (TCRS) also controls CPB production in broth cultures. Both the Agr-like QS and VirS/VirR systems are important when C. perfringens senses enterocyte-like Caco-2 cells and responds by upregulating CPB production; however, only the Agr-like QS system is needed for host cell-induced ETX production. These in vitro observations have pathophysiologic relevance since both the VirS/VirR and Agr-like QS signaling systems are required for C. perfringens strain CN3685 to produce CPB in vivo and to cause enteritis or enterotoxemia. Thus, apparently upon sensing its presence in the intestines, C. perfringens utilizes QS and TCRS signaling to produce toxins necessary for intestinal virulence.
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Affiliation(s)
- Jianming Chen
- Department of Microbiology and Molecular Genetics; University of Pittsburgh School of Medicine; Pittsburgh, PA USA
| | - Menglin Ma
- Department of Microbiology and Molecular Genetics; University of Pittsburgh School of Medicine; Pittsburgh, PA USA
| | - Francisco A Uzal
- California Animal Health and Food Safety Laboratory; San Bernadino Branch, School of Veterinary Medicine; University of California Davis; San Bernadino, CA USA
| | - Bruce A McClane
- Department of Microbiology and Molecular Genetics; University of Pittsburgh School of Medicine; Pittsburgh, PA USA,Correspondence to: Bruce A McClane,
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27
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Carter GP, Cheung JK, Larcombe S, Lyras D. Regulation of toxin production in the pathogenic clostridia. Mol Microbiol 2013; 91:221-31. [DOI: 10.1111/mmi.12469] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Glen P. Carter
- Department of Microbiology; Monash University; Clayton Vic. 3800 Australia
| | - Jackie K. Cheung
- Department of Microbiology; Monash University; Clayton Vic. 3800 Australia
| | - Sarah Larcombe
- Department of Microbiology; Monash University; Clayton Vic. 3800 Australia
| | - Dena Lyras
- Department of Microbiology; Monash University; Clayton Vic. 3800 Australia
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28
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Connan C, Denève C, Mazuet C, Popoff MR. Regulation of toxin synthesis in Clostridium botulinum and Clostridium tetani. Toxicon 2013; 75:90-100. [DOI: 10.1016/j.toxicon.2013.06.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Revised: 05/25/2013] [Accepted: 06/04/2013] [Indexed: 01/11/2023]
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29
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Structural requirement in Clostridium perfringens collagenase mRNA 5' leader sequence for translational induction through small RNA-mRNA base pairing. J Bacteriol 2013; 195:2937-46. [PMID: 23585542 DOI: 10.1128/jb.00148-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The Gram-positive anaerobic bacterium Clostridium perfringens is pathogenic to humans and animals, and the production of its toxins is strictly regulated during the exponential phase. We recently found that the 5' leader sequence of the colA transcript encoding collagenase, which is a major toxin of this organism, is processed and stabilized in the presence of the small RNA VR-RNA. The primary colA 5'-untranslated region (5'UTR) forms a long stem-loop structure containing an internal bulge and masks its own ribosomal binding site. Here we found that VR-RNA directly regulates colA expression through base pairing with colA mRNA in vivo. However, when the internal bulge structure was closed by point mutations in colA mRNA, translation ceased despite the presence of VR-RNA. In addition, a mutation disrupting the colA stem-loop structure induced mRNA processing and ColA-FLAG translational activation in the absence of VR-RNA, indicating that the stem-loop and internal bulge structure of the colA 5' leader sequence is important for regulation by VR-RNA. On the other hand, processing was required for maximal ColA expression but was not essential for VR-RNA-dependent colA regulation. Finally, colA processing and translational activation were induced at a high temperature without VR-RNA. These results suggest that inhibition of the colA 5' leader structure through base pairing is the primary role of VR-RNA in colA regulation and that the colA 5' leader structure is a possible thermosensor.
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30
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Park S, Park M, Rafii F. Comparative transcription analysis and toxin production of two fluoroquinolone-resistant mutants of Clostridium perfringens. BMC Microbiol 2013; 13:50. [PMID: 23452396 PMCID: PMC3599539 DOI: 10.1186/1471-2180-13-50] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2012] [Accepted: 02/18/2013] [Indexed: 11/10/2022] Open
Abstract
Background Fluoroquinolone use has been listed as a risk factor for the emergence of virulent clinical strains of some bacteria. The aim of our study was to evaluate the effect of fluoroquinolone (gatifloxacin) resistance selection on differential gene expression, including the toxin genes involved in virulence, in two fluoroquinolone-resistant strains of Clostridium perfringens by comparison with their wild-type isogenic strains. Results DNA microarray analyses were used to compare the gene transcription of two wild types, NCTR and ATCC 13124, with their gatifloxacin-resistant mutants, NCTRR and 13124R. Transcription of a variety of genes involved in bacterial metabolism was either higher or lower in the mutants than in the wild types. Some genes, including genes for toxins and regulatory genes, were upregulated in NCTRR and downregulated in 13124R. Transcription analysis by quantitative real-time PCR (qRT-PCR) confirmed the altered expression of many of the genes that were affected differently in the fluoroquinolone-resistant mutants and wild types. The levels of gene expression and enzyme production for the toxins phospholipase C, perfringolysin O, collagenase and clostripain had decreased in 13124R and increased in NCTRR in comparison with the wild types. After centrifugation, the cytotoxicity of the supernatants of NCTRR and 13224R cultures for mouse peritoneal macrophages confirmed the increased cytotoxicity of NCTRR and the decreased cytotoxicity of 13124R in comparison with the respective wild types. Fluoroquinolone resistance selection also affected cell shape and colony morphology in both strains. Conclusion Our results indicate that gatifloxacin resistance selection was associated with altered gene expression in two C. perfringens strains and that the effect was strain-specific. This study clearly demonstrates that bacterial exposure to fluoroquinolones may affect virulence (toxin production) in addition to drug resistance.
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Affiliation(s)
- Sunny Park
- Division of Microbiology, National Center for Toxicological Research, US Food and Drug Administration, Jefferson, AR, USA
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Burkholderia xenovorans RcoM(Bx)-1, a transcriptional regulator system for sensing low and persistent levels of carbon monoxide. J Bacteriol 2012; 194:5803-16. [PMID: 22923594 DOI: 10.1128/jb.01024-12] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The single-component RcoM transcription factor couples an N-terminally bound heme cofactor with a C-terminal "LytTR" DNA-binding domain. Here the RcoM(Bx)-1 protein from Burkholderia xenovorans LB400 was heterologously expressed and then purified in a form with minimal bound CO (~10%) and was found to stably bind this effector with a nanomolar affinity. DNase I protection assays demonstrated that the CO-associated form binds with a micromolar affinity to two ~60-bp DNA regions, each comprised of a novel set of three direct-repeat binding sites spaced 21 bp apart on center. Binding to each region was independent, while binding to the triplet binding sites within a region was cooperative, depended upon spacing and sequence, and was marked by phased DNase I hyperactivity and protection patterns consistent with considerable changes in the DNA conformation of the nucleoprotein complex. Each protected binding site spanned a conserved motif (5'-TTnnnG-3') that was present, in triplicate, in putative RcoM-binding regions of more than a dozen organisms. In vivo screens confirmed the functional importance of the conserved "TTnnnG" motif residues and their triplet arrangement and were also used to determine an improved binding motif [5'-CnnC(C/A)(G/A)TTCAnG-3'] that more closely corresponds to canonical LytTR domain/DNA-binding sites. A low-affinity but CO-dependent binding of RcoM(Bx)-1 to a variety of DNA probes was demonstrated in vitro. We posit that for the RcoM(Bx)-1 protein, the high CO affinity combined with multiple low-affinity DNA-binding events constitutes a transcriptional "accumulating switch" that senses low but persistent CO levels.
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Connan C, Brueggemann H, Mazuet C, Raffestin S, Cayet N, Popoff MR. Two-component systems are involved in the regulation of botulinum neurotoxin synthesis in Clostridium botulinum type A strain Hall. PLoS One 2012; 7:e41848. [PMID: 22848632 PMCID: PMC3406050 DOI: 10.1371/journal.pone.0041848] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Accepted: 06/29/2012] [Indexed: 11/30/2022] Open
Abstract
Clostridium botulinum synthesizes a potent neurotoxin (BoNT) which associates with non-toxic proteins (ANTPs) to form complexes of various sizes. The bont and antp genes are clustered in two operons. In C. botulinum type A, bont/A and antp genes are expressed during the end of the exponential growth phase and the beginning of the stationary phase under the control of an alternative sigma factor encoded by botR/A, which is located between the two operons. In the genome of C. botulinum type A strain Hall, 30 gene pairs predicted to encode two-component systems (TCSs) and 9 orphan regulatory genes have been identified. Therefore, 34 Hall isogenic antisense strains on predicted regulatory genes (29 TCSs and 5 orphan regulatory genes) have been obtained by a mRNA antisense procedure. Two TCS isogenic antisense strains showed more rapid growth kinetics and reduced BoNT/A production than the control strain, as well as increased bacterial lysis and impairment of the bacterial cell wall structure. Three other TCS isogenic antisense strains induced a low level of BoNT/A and ANTP production. Interestingly, reduced expression of bont/A and antp genes was shown to be independent of botR/A. These results indicate that BoNT/A synthesis is under the control of a complex network of regulation including directly at least three TCSs.
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Affiliation(s)
- Chloé Connan
- Institut Pasteur, Bactéries anaérobies et Toxines, Paris, France
| | | | | | | | - Nadège Cayet
- Institut Pasteur, Plateforme de Microscopie Ultrastructurale, Paris, France
| | - Michel R. Popoff
- Institut Pasteur, Bactéries anaérobies et Toxines, Paris, France
- * E-mail:
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Brantl S. Acting antisense: plasmid- and chromosome-encoded sRNAs from Gram-positive bacteria. Future Microbiol 2012; 7:853-71. [DOI: 10.2217/fmb.12.59] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
sRNAs that act by base pairing were first discovered in plasmids, phages and transposons, where they control replication, maintenance and transposition. Since 2001, however, computational searches were applied that led to the discovery of a plethora of sRNAs in bacterial chromosomes. Whereas the majority of these chromsome-encoded sRNAs have been investigated in Escherichia coli, Salmonella and other Gram-negative bacteria, only a few well-studied examples are known from Gram-positive bacteria. Here, the author summarizes our current knowledge on plasmid- and chromosome-encoded sRNAs from Gram-positive species, thereby focusing on regulatory mechanisms used by these RNAs and their biological role in complex networks. Furthermore, regulatory factors that control the expression of these RNAs will be discussed and differences between sRNAs from Gram-positive and Gram-negative bacteria highlighted. The main emphasis of this review is on sRNAs that act by base pairing (i.e., by an antisense mechanism). Thereby, both plasmid-encoded and chromosome-encoded sRNAs will be considered.
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Affiliation(s)
- Sabine Brantl
- AG Bakteriengenetik, Friedrich-Schiller-Universität Jena, Philosophenweg 12, D-07743 Jena, Germany
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Nowell VJ, Kropinski AM, Songer JG, MacInnes JI, Parreira VR, Prescott JF. Genome sequencing and analysis of a type A Clostridium perfringens isolate from a case of bovine clostridial abomasitis. PLoS One 2012; 7:e32271. [PMID: 22412860 PMCID: PMC3297601 DOI: 10.1371/journal.pone.0032271] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2011] [Accepted: 01/24/2012] [Indexed: 01/25/2023] Open
Abstract
Clostridium perfringens is a common inhabitant of the avian and mammalian gastrointestinal tracts and can behave commensally or pathogenically. Some enteric diseases caused by type A C. perfringens, including bovine clostridial abomasitis, remain poorly understood. To investigate the potential basis of virulence in strains causing this disease, we sequenced the genome of a type A C. perfringens isolate (strain F262) from a case of bovine clostridial abomasitis. The ∼3.34 Mbp chromosome of C. perfringens F262 is predicted to contain 3163 protein-coding genes, 76 tRNA genes, and an integrated plasmid sequence, Cfrag (∼18 kb). In addition, sequences of two complete circular plasmids, pF262C (4.8 kb) and pF262D (9.1 kb), and two incomplete plasmid fragments, pF262A (48.5 kb) and pF262B (50.0 kb), were identified. Comparison of the chromosome sequence of C. perfringens F262 to complete C. perfringens chromosomes, plasmids and phages revealed 261 unique genes. No novel toxin genes related to previously described clostridial toxins were identified: 60% of the 261 unique genes were hypothetical proteins. There was a two base pair deletion in virS, a gene reported to encode the main sensor kinase involved in virulence gene activation. Despite this frameshift mutation, C. perfringens F262 expressed perfringolysin O, alpha-toxin and the beta2-toxin, suggesting that another regulation system might contribute to the pathogenicity of this strain. Two complete plasmids, pF262C (4.8 kb) and pF262D (9.1 kb), unique to this strain of C. perfringens were identified.
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Affiliation(s)
- Victoria J Nowell
- Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada
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Sugar inhibits the production of the toxins that trigger clostridial gas gangrene. Microb Pathog 2011; 52:85-91. [PMID: 22079896 DOI: 10.1016/j.micpath.2011.10.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2011] [Revised: 10/24/2011] [Accepted: 10/27/2011] [Indexed: 01/22/2023]
Abstract
Histotoxic strains of Clostridium perfringens cause human gas gangrene, a devastating infection during which potent tissue-degrading toxins are produced and secreted. Although this pathogen only grows in anaerobic-nutrient-rich habitats such as deep wounds, very little is known regarding how nutritional signals influence gas gangrene-related toxin production. We hypothesize that sugars, which have been used throughout history to prevent wound infection, may represent a nutritional signal against gas gangrene development. Here we demonstrate, for the first time, that sugars (sucrose, glucose) inhibited the production of the main protein toxins, PLC (alpha-toxin) and PFO (theta-toxin), responsible for the onset and progression of gas gangrene. Transcription analysis experiments using plc-gusA and pfoA-gusA reporter fusions as well as RT-PCR analysis of mRNA transcripts confirmed that sugar represses plc and pfoA expression. In contrast an isogenic C. perfringens strain that is defective in CcpA, the master transcription factor involved in carbon catabolite response, was completely resistant to the sugar-mediated inhibition of PLC and PFO toxin production. Furthermore, the production of PLC and PFO toxins in the ccpA mutant strain was several-fold higher than the toxin production found in the wild type strain. Therefore, CcpA is the primary or unique regulatory protein responsible for the carbon catabolite (sugar) repression of toxin production of this pathogen. The present results are analyzed in the context of the role of CcpA for the development and aggressiveness of clostridial gas gangrene and the well-known, although poorly understood, anti-infective and wound healing effects of sugars and related substances.
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Complex transcriptional regulation of citrate metabolism in Clostridium perfringens. Anaerobe 2011; 18:48-54. [PMID: 21945821 DOI: 10.1016/j.anaerobe.2011.09.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 08/26/2011] [Accepted: 09/12/2011] [Indexed: 11/23/2022]
Abstract
A Gram-positive, spore-forming bacterium, Clostridium perfringens, possesses genes for citrate metabolism, which might play an important role in the utilization of citrate as a sole carbon source. In this study, we identified a chromosomal citCDEFX-mae-citS operon in C. perfringens strain 13, which is transcribed on three mRNAs of different sizes. Expression of the cit operon was significantly induced when 5 mM extracellular citrate was added to the growth medium. Most interestingly, three regulatory systems were found to be involved in the regulation of the expression of cit genes: 1) the two upstream divergent genes citG and citI; 2) two different two-component regulatory systems, CitA/CitB (TCS6 consisted of CPE0531/CPE0532) and TCS5 (CPE0518/CPE0519); and 3) the global two-component VirR/VirS-VR-RNA regulatory system known to regulate various genes for toxins and degradative enzymes. Our results suggest that in C. perfringens the citrate metabolism might be strictly controlled by a complex regulatory system.
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Chakravorty A, Awad MM, Hiscox TJ, Cheung JK, Carter GP, Choo JM, Lyras D, Rood JI. The cysteine protease α-clostripain is not essential for the pathogenesis of Clostridium perfringens-mediated myonecrosis. PLoS One 2011; 6:e22762. [PMID: 21829506 PMCID: PMC3146509 DOI: 10.1371/journal.pone.0022762] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2011] [Accepted: 06/28/2011] [Indexed: 11/25/2022] Open
Abstract
Clostridium perfringens is the causative agent of clostridial myonecrosis or gas gangrene and produces many different extracellular toxins and enzymes, including the cysteine protease α-clostripain. Mutation of the α-clostripain structural gene, ccp, alters the turnover of secreted extracellular proteins in C. perfringens, but the role of α-clostripain in disease pathogenesis is not known. We insertionally inactivated the ccp gene C. perfringens strain 13 using TargeTron technology, constructing a strain that was no longer proteolytic on skim milk agar. Quantitative protease assays confirmed the absence of extracellular protease activity, which was restored by complementation with the wild-type ccp gene. The role of α-clostripain in virulence was assessed by analysing the isogenic wild-type, mutant and complemented strains in a mouse myonecrosis model. The results showed that although α-clostripain was the major extracellular protease, mutation of the ccp gene did not alter either the progression or the development of disease. These results do not rule out the possibility that this extracellular enzyme may still have a role in the early stages of the disease process.
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Affiliation(s)
| | - Milena M. Awad
- Department of Microbiology, Monash University, Clayton, Australia
| | - Thomas J. Hiscox
- Department of Microbiology, Monash University, Clayton, Australia
| | - Jackie K. Cheung
- Department of Microbiology, Monash University, Clayton, Australia
| | - Glen P. Carter
- Department of Microbiology, Monash University, Clayton, Australia
| | - Jocelyn M. Choo
- Department of Microbiology, Monash University, Clayton, Australia
| | - Dena Lyras
- Department of Microbiology, Monash University, Clayton, Australia
| | - Julian I. Rood
- Department of Microbiology, Monash University, Clayton, Australia
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Bryant AE, Stevens DL. Clostridial myonecrosis: new insights in pathogenesis and management. Curr Infect Dis Rep 2011; 12:383-91. [PMID: 21308521 DOI: 10.1007/s11908-010-0127-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Clostridial myonecrosis remains an important cause of human morbidity and mortality worldwide. Although traumatic gas gangrene can be readily diagnosed from clinical findings and widely available technologies, spontaneous gas gangrene is more insidious, and gynecologic infections due to Clostridium sordellii progress so rapidly that death often precedes diagnosis. In each case, extensive tissue destruction and the subsequent systemic manifestations are mediated directly and indirectly by potent bacterial exotoxins. The management triumvirate of timely diagnosis, thorough surgical removal of necrotic tissue, and treatment with antibiotics that inhibit toxin synthesis remains the gold standard of care. Yet, despite these measures, mortality remains 30% to 100% and survivors often must cope with life-altering amputations. Recent insights regarding the genetic regulation of toxin production, the molecular mechanisms of toxin-induced host cell dysfunction, and the roles of newly described toxins in pathogenesis suggest that novel prevention, diagnostic, and treatment modalities may be on the horizon for these devastating infections.
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Affiliation(s)
- Amy E Bryant
- Infectious Diseases Section, Veterans Affairs Medical Center, 500 West Fort Street (Bldg 45), Boise, ID, 83702, USA,
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A novel toxin regulator, the CPE1446-CPE1447 protein heteromeric complex, controls toxin genes in Clostridium perfringens. J Bacteriol 2011; 193:4417-24. [PMID: 21725013 DOI: 10.1128/jb.00262-11] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium perfringens is a Gram-positive anaerobic spore-forming bacterium that is widespread in environmental soil and sewage, as well as in animal intestines. It is also a causative agent of diseases in humans and other animals, and it produces numerous extracellular enzymes and toxins. Although these toxins have been characterized in detail, regulators of toxin genes are less well understood. The present study identified CPE1447 and CPE1446 as novel regulators of toxin gene expression. CPE1447 and CPE1446 are cotranscribed as an operon, and the encoded proteins have a helix-turn-helix (HTH) motif at the N termini of their amino acid sequences, suggesting that CPE1447 and CPE1446 control the target genes as transcriptional regulators. The expression of several genes encoding toxins was changed in both a CPE1446 mutant and a CPE1447-CPE1446 deletion mutant. Complementation of CPE1446 and CPE1447 revealed that CPE1447 and CPE1446 coordinately regulate their target genes. CPE1447 protein was coprecipitated with His-tagged CPE1446 protein, indicating that the CPE1447 and CPE1446 proteins form a stable complex in C. perfringens under their native conditions. Although the small RNA that regulates several genes under the VirR/VirS two-component system (VR-RNA) positively affected CPE1447-CPE1446 mRNA expression, it did not control expression of the CPE1447-CPE1446 regulon, demonstrating that CPE1447 and CPE1446 regulate a different set of toxin genes from the VirR/VirS-VR-RNA cascade.
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Regulation of virulence by the RevR response regulator in Clostridium perfringens. Infect Immun 2011; 79:2145-53. [PMID: 21402758 DOI: 10.1128/iai.00060-11] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Clostridium perfringens causes clostridial myonecrosis or gas gangrene and produces several extracellular hydrolytic enzymes and toxins, many of which are regulated by the VirSR signal transduction system. The revR gene encodes a putative orphan response regulator that has similarity to the YycF (WalR), VicR, PhoB, and PhoP proteins from other Gram-positive bacteria. RevR appears to be a classical response regulator, with an N-terminal receiver domain and a C-terminal domain with a putative winged helix-turn-helix DNA binding region. To determine its functional role, a revR mutant was constructed by allelic exchange and compared to the wild type by microarray analysis. The results showed that more than 100 genes were differentially expressed in the mutant, including several genes involved in cell wall metabolism. The revR mutant had an altered cellular morphology; unlike the short rods observed with the wild type, the mutant cells formed long filaments. These changes were reversed upon complementation with a plasmid that carried the wild-type revR gene. Several genes encoding extracellular hydrolytic enzymes (sialidase, hyaluronidase, and α-clostripain) were differentially expressed in the revR mutant. Quantitative enzyme assays confirmed that these changes led to altered enzyme activity and that complementation restored the wild-type phenotype. Most importantly, the revR mutant was attenuated for virulence in the mouse myonecrosis model compared to the wild type and the complemented strains. These results provide evidence that RevR regulates virulence in C. perfringens; it is the first response regulator other than VirR to be shown to regulate virulence in this important pathogen.
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Development and application of a method for counterselectable in-frame deletion in Clostridium perfringens. Appl Environ Microbiol 2010; 77:1375-82. [PMID: 21183644 DOI: 10.1128/aem.01572-10] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Many pathogenic clostridial species produce toxins and enzymes. To facilitate genome-wide identification of virulence factors and biotechnological application of their useful products, we have developed a markerless in-frame deletion method for Clostridium perfringens which allows efficient counterselection and multiple-gene disruption. The system comprises a galKT gene disruptant and a suicide galK plasmid into which two fragments of a target gene for in-frame deletion are cloned. The system was shown to be accurate and simple by using it to disrupt the alpha-toxin gene of the organism. It was also used to construct of two different virulence-attenuated strains, ΗΝ1303 and HN1314: the former is a disruptant of the virRS operon, which regulates the expression of virulence factors, and the latter is a disruptant of the six genes encoding the α, θ, and κ toxins; a clostripain-like protease; a 190-kDa secretory protein; and a putative cell wall lytic endopeptidase. Comparison of the two disruptants in terms of growth ability and the background levels of secreted proteins showed that HN1314 is more useful than ΗΝ1303 as a host for the large-scale production of recombinant proteins.
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Papenfort K, Vogel J. Regulatory RNA in bacterial pathogens. Cell Host Microbe 2010; 8:116-27. [PMID: 20638647 DOI: 10.1016/j.chom.2010.06.008] [Citation(s) in RCA: 249] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2010] [Revised: 05/18/2010] [Accepted: 06/22/2010] [Indexed: 01/26/2023]
Abstract
Bacteria constitute a large and diverse class of infectious agents, causing devastating diseases in humans, animals, and plants. Our understanding of gene expression control, which forms the basis for successful prevention and treatment strategies, has until recently neglected the many roles that regulatory RNAs might have in bacteria. In recent years, several such regulators have been found to facilitate host-microbe interactions and act as key switches between saprophytic and pathogenic lifestyles. This review covers the versatile regulatory RNA mechanisms employed by bacterial pathogens and highlights the dynamic interplay between riboregulation and virulence factor expression.
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Affiliation(s)
- Kai Papenfort
- RNA Biology Group, Max Planck Institute for Infection Biology, Charitéplatz 1, D-10117 Berlin, Germany
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Obana N, Shirahama Y, Abe K, Nakamura K. Stabilization of Clostridium perfringens collagenase mRNA by VR-RNA-dependent cleavage in 5′ leader sequence. Mol Microbiol 2010; 77:1416-28. [DOI: 10.1111/j.1365-2958.2010.07258.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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André G, Haudecoeur E, Monot M, Ohtani K, Shimizu T, Dupuy B, Martin-Verstraete I. Global regulation of gene expression in response to cysteine availability in Clostridium perfringens. BMC Microbiol 2010; 10:234. [PMID: 20822510 PMCID: PMC2940859 DOI: 10.1186/1471-2180-10-234] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Accepted: 09/07/2010] [Indexed: 11/24/2022] Open
Abstract
Background Cysteine has a crucial role in cellular physiology and its synthesis is tightly controlled due to its reactivity. However, little is known about the sulfur metabolism and its regulation in clostridia compared with other firmicutes. In Clostridium perfringens, the two-component system, VirR/VirS, controls the expression of the ubiG operon involved in methionine to cysteine conversion in addition to the expression of several toxin genes. The existence of links between the C. perfringens virulence regulon and sulfur metabolism prompted us to analyze this metabolism in more detail. Results We first performed a tentative reconstruction of sulfur metabolism in C. perfringens and correlated these data with the growth of strain 13 in the presence of various sulfur sources. Surprisingly, C. perfringens can convert cysteine to methionine by an atypical still uncharacterized pathway. We further compared the expression profiles of strain 13 after growth in the presence of cystine or homocysteine that corresponds to conditions of cysteine depletion. Among the 177 genes differentially expressed, we found genes involved in sulfur metabolism and controlled by premature termination of transcription via a cysteine specific T-box system (cysK-cysE, cysP1 and cysP2) or an S-box riboswitch (metK and metT). We also showed that the ubiG operon was submitted to a triple regulation by cysteine availability via a T-box system, by the VirR/VirS system via the VR-RNA and by the VirX regulatory RNA. In addition, we found that expression of pfoA (theta-toxin), nagL (one of the five genes encoding hyaluronidases) and genes involved in the maintenance of cell redox status was differentially expressed in response to cysteine availability. Finally, we showed that the expression of genes involved in [Fe-S] clusters biogenesis and of the ldh gene encoding the lactate dehydrogenase was induced during cysteine limitation. Conclusion Several key functions for the cellular physiology of this anaerobic bacterium were controlled in response to cysteine availability. While most of the genes involved in sulfur metabolism are regulated by premature termination of transcription, other still uncharacterized mechanisms of regulation participated in the induction of gene expression during cysteine starvation.
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Affiliation(s)
- Gaelle André
- Institut Pasteur, Unité de Génétique des Génomes Bactériens and Unité des Bactéries Anaérobies et Toxines, 28 rue du Docteur Roux, 75015 Paris, France
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The VirSR two-component signal transduction system regulates NetB toxin production in Clostridium perfringens. Infect Immun 2010; 78:3064-72. [PMID: 20457789 DOI: 10.1128/iai.00123-10] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clostridium perfringens causes several diseases in domestic livestock, including necrotic enteritis in chickens, which is of concern to the poultry industry due to its health implications and associated economic cost. The novel pore-forming toxin NetB is a critical virulence factor in the pathogenesis of this disease. In this study, we have examined the regulation of NetB toxin production. In C. perfringens, the quorum sensing-dependent VirSR two-component signal transduction system regulates genes encoding several toxins and extracellular enzymes. Analysis of the sequence upstream of the netB gene revealed the presence of potential DNA binding sites, or VirR boxes, that are recognized by the VirR response regulator. In vitro binding experiments showed that purified VirR was able to recognize and bind to these netB-associated VirR boxes. Furthermore, using a reporter gene assay, the netB VirR boxes were shown to be functional. Mutation of the virR gene in two avian C. perfringens strains was shown to significantly reduce the production of the NetB toxin; culture supernatants derived from these strains were no longer cytotoxic to Leghorn male hepatoma cells. Complementation with the virRS operon restored the toxin phenotypes to wild type. The results also showed that the VirSR two-component system regulates the expression of netB at the level of transcription. We postulate that in the gastrointestinal tract of infected birds, NetB production is upregulated when the population of C. perfringens cells reaches a threshold level that leads to activation of the VirSR system.
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Transcriptional regulation of hemO encoding heme oxygenase in Clostridium perfringens. J Microbiol 2010; 48:96-101. [DOI: 10.1007/s12275-009-0384-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2009] [Accepted: 12/28/2009] [Indexed: 10/19/2022]
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Frandi A, Mengoni A, Brilli M. Comparative genomics of VirR regulons in Clostridium perfringens strains. BMC Microbiol 2010; 10:65. [PMID: 20184757 PMCID: PMC2838878 DOI: 10.1186/1471-2180-10-65] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2009] [Accepted: 02/25/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Clostridium perfringens is a Gram-positive anaerobic bacterium causing severe diseases such as gas gangrene and pseudomembranosus colitis, that are generally due to the secretion of powerful extracellular toxins. The expression of toxin genes is mainly regulated by VirR, the response regulator of a two-component system. Up to now few targets only are known for this regulator and mainly in one strain (Strain 13). Due to the high genomic and phenotypic variability in toxin production by different strains, the development of effective strategies to counteract C. perfringens infections requires methodologies to reconstruct the VirR regulon from genome sequences. RESULTS We implemented a two step computational strategy allowing to consider available information concerning VirR binding sites in a few species to scan all genomes of the same species, assuming the VirR targets are at least partially conserved across these strains. Results obtained are in agreement with previous works where experimental validation of the promoters have been performed and showed the presence of a core and an accessory regulon of VirR in C. perfringens strains with three target genes also located on plasmids. Moreover, the type E strain JGS1987 has the largest predicted regulon with as many as 10 VirR targets not found in the other genomes. CONCLUSIONS In this work we exploited available experimental information concerning the targets of the VirR toxin regulator in one C. perfringens strain to obtain plausible predictions concerning target genes in genomes and plasmids of nearby strains. Our predictions are available for wet-lab researchers working on less characterized C. perfringens strains that can thus design focused experiments reducing the search space of their experiments and increasing the probability of characterizing positive targets with less efforts. Main result was that the VirR regulon is variable in different C. perfringens strains with 4 genes controlled in all but one strains and most genes controlled in one or two strains only.
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Affiliation(s)
- Antonio Frandi
- Université de Lyon, F-69000, Lyon, Université Lyon 1, CNRS, France
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Abstract
Clostridia produce the highest number of toxins of any type of bacteria and are involved in severe diseases in humans and other animals. Most of the clostridial toxins are pore-forming toxins responsible for gangrenes and gastrointestinal diseases. Among them, perfringolysin has been extensively studied and it is the paradigm of the cholesterol-dependent cytolysins, whereas Clostridium perfringens epsilon-toxin and Clostridium septicum alpha-toxin, which are related to aerolysin, are the prototypes of clostridial toxins that form small pores. Other toxins active on the cell surface possess an enzymatic activity, such as phospholipase C and collagenase, and are involved in the degradation of specific cell-membrane or extracellular-matrix components. Three groups of clostridial toxins have the ability to enter cells: large clostridial glucosylating toxins, binary toxins and neurotoxins. The binary and large clostridial glucosylating toxins alter the actin cytoskeleton by enzymatically modifying the actin monomers and the regulatory proteins from the Rho family, respectively. Clostridial neurotoxins proteolyse key components of neuroexocytosis. Botulinum neurotoxins inhibit neurotransmission at neuromuscular junctions, whereas tetanus toxin targets the inhibitory interneurons of the CNS. The high potency of clostridial toxins results from their specific targets, which have an essential cellular function, and from the type of modification that they induce. In addition, clostridial toxins are useful pharmacological and biological tools.
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Affiliation(s)
- Michel R Popoff
- Institut Pasteur, Bactéries Anaérobies et Toxines, 75724 Paris cedex 15, France.
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Uzal FA, Vidal JE, McClane BA, Gurjar AA. Clostridium Perfringens Toxins Involved in Mammalian Veterinary Diseases. THE OPEN TOXINOLOGY JOURNAL 2010; 2:24-42. [PMID: 24511335 PMCID: PMC3917546] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Clostridium perfringens is a gram-positive anaerobic rod that is classified into 5 toxinotypes (A, B, C, D, and E) according to the production of 4 major toxins, namely alpha (CPA), beta (CPB), epsilon (ETX) and iota (ITX). However, this microorganism can produce up to 16 toxins in various combinations, including lethal toxins such as perfringolysin O (PFO), enterotoxin (CPE), and beta2 toxin (CPB2). Most diseases caused by this microorganism are mediated by one or more of these toxins. The role of CPA in intestinal disease of mammals is controversial and poorly documented, but there is no doubt that this toxin is essential in the production of gas gangrene of humans and several animal species. CPB produced by C. perfringens types B and C is responsible for necrotizing enteritis and enterotoxemia mainly in neonatal individuals of several animal species. ETX produced by C. perfringens type D is responsible for clinical signs and lesions of enterotoxemia, a predominantly neurological disease of sheep and goats. The role of ITX in disease of animals is poorly understood, although it is usually assumed that the pathogenesis of intestinal diseases produced by C. perfringens type E is mediated by this toxin. CPB2, a necrotizing and lethal toxin that can be produced by all types of C. perfringens, has been blamed for disease in many animal species, but little information is currently available to sustain or rule out this claim. CPE is an important virulence factor for C. perfringens type A gastrointestinal disease in humans and dogs; however, the data implicating CPE in other animal diseases remains ambiguous. PFO does not seem to play a direct role as the main virulence factor for animal diseases, but it may have a synergistic role with CPA-mediated gangrene and ETX-mediated enterotoxemia. The recent improvement of animal models for C. perfringens infection and the use of toxin gene knock-out mutants have demonstrated the specific pathogenic role of several toxins of C. perfringens in animal disease. These research tools are helping us to establish the role of each C. perfringens toxin in animal disease, to investigate the in vivo mechanism of action of these toxins, and to develop more effective vaccines against diseases produced by these microorganisms.
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Affiliation(s)
- F. A. Uzal
- California Animal Health and Food Safety Laboratory System, San Bernardino Branch, School of Veterinary Medicine, University of California, Davis, San Bernardino, CA 92408, USA,Address correspondence to this author at the California Animal Health and Food Safety Laboratory System, San Bernardino Branch, School of Veterinary Medicine, University of California, Davis, San Bernardino, CA 92408, USA;
| | - J. E. Vidal
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - B. A. McClane
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA,Department of Molecular Virology and Microbiology Graduate Program, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
| | - A. A. Gurjar
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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Tsui HCT, Mukherjee D, Ray VA, Sham LT, Feig AL, Winkler ME. Identification and characterization of noncoding small RNAs in Streptococcus pneumoniae serotype 2 strain D39. J Bacteriol 2010; 192:264-79. [PMID: 19854910 PMCID: PMC2798261 DOI: 10.1128/jb.01204-09] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2009] [Accepted: 10/12/2009] [Indexed: 11/20/2022] Open
Abstract
We report a search for small RNAs (sRNAs) in the low-GC, gram-positive human pathogen Streptococcus pneumoniae. Based on bioinformatic analyses by Livny et al. (J. Livny, A. Brencic, S. Lory, and M. K. Waldor, Nucleic Acids Res. 34:3484-3493, 2006), we tested 40 candidates by Northern blotting and confirmed the expression of nine new and one previously reported (CcnA) sRNAs in strain D39. CcnA is one of five redundant sRNAs reported by Halfmann et al. (A. Halfmann, M. Kovacs, R. Hakenbeck, and R. Bruckner, Mol. Microbiol. 66:110-126, 2007) that are positively controlled by the CiaR response regulator. We characterized 3 of these 14 sRNAs: Spd-sr17 (144 nucleotides [nt]; decreased in stationary phase), Spd-sr37 (80 nt; strongly expressed in all growth phases), and CcnA (93 nt; induced by competence stimulatory peptide). Spd-sr17 and CcnA likely fold into structures containing single-stranded regions between hairpin structures, whereas Spd-sr37 forms a base-paired structure. Primer extension mapping and ectopic expression in deletion/insertion mutants confirmed the independent expression of the three sRNAs. Microarray analyses indicated that insertion/deletion mutants in spd-sr37 and ccnA exerted strong cis-acting effects on the transcription of adjacent genes, indicating that these sRNA regions are also cotranscribed in operons. Deletion or overexpression of the three sRNAs did not cause changes in growth, certain stress responses, global transcription, or virulence. Constitutive ectopic expression of CcnA reversed some phenotypes of D39 Delta ciaR mutants, but attempts to link CcnA to -E to comC as a target were inconclusive in ciaR(+) strains. These results show that S. pneumoniae, which lacks known RNA chaperones, expresses numerous sRNAs, but three of these sRNAs do not strongly affect common phenotypes or transcription patterns.
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Affiliation(s)
- Ho-Ching Tiffany Tsui
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
| | - Dhriti Mukherjee
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
| | - Valerie A. Ray
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
| | - Lok-To Sham
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
| | - Andrew L. Feig
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
| | - Malcolm E. Winkler
- Department of Biology, Indiana University—Bloomington, Bloomington, Indiana 47405, Department of Chemistry, Wayne State University, 5101 Cass Ave., Detroit, Michigan 48202
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