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Woelfel S, Silva MS, Stecher B. Intestinal colonization resistance in the context of environmental, host, and microbial determinants. Cell Host Microbe 2024; 32:820-836. [PMID: 38870899 DOI: 10.1016/j.chom.2024.05.002] [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: 02/15/2024] [Revised: 05/07/2024] [Accepted: 05/07/2024] [Indexed: 06/15/2024]
Abstract
Microbial communities that colonize the human gastrointestinal (GI) tract defend against pathogens through a mechanism known as colonization resistance (CR). Advances in technologies such as next-generation sequencing, gnotobiotic mouse models, and bacterial cultivation have enhanced our understanding of the underlying mechanisms and the intricate microbial interactions involved in CR. Rather than being attributed to specific microbial clades, CR is now understood to arise from a dynamic interplay between microbes and the host and is shaped by metabolic, immune, and environmental factors. This evolving perspective underscores the significance of contextual factors, encompassing microbiome composition and host conditions, in determining CR. This review highlights recent research that has shifted its focus toward elucidating how these factors interact to either promote or impede enteric infections. It further discusses future research directions to unravel the complex relationship between host, microbiota, and environmental determinants in safeguarding against GI infections to promote human health.
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Affiliation(s)
- Simon Woelfel
- Max von Pettenkofer-Institute for Hygiene and Clinical Microbiology, Ludwig Maximilian University of Munich, 80336 Munich, Germany
| | - Marta Salvado Silva
- Max von Pettenkofer-Institute for Hygiene and Clinical Microbiology, Ludwig Maximilian University of Munich, 80336 Munich, Germany
| | - Bärbel Stecher
- Max von Pettenkofer-Institute for Hygiene and Clinical Microbiology, Ludwig Maximilian University of Munich, 80336 Munich, Germany; German Center for Infection Research (DZIF), partner site LMU Munich, Munich, Germany.
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2
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Hu Z, Ojima S, Zhu Z, Yu X, Sugiyama M, Haneda T, Okamura M, Ono HK, Hu DL. Salmonella pathogenicity island-14 is a critical virulence factor responsible for systemic infection in chickens caused by Salmonella gallinarum. Front Vet Sci 2024; 11:1401392. [PMID: 38846788 PMCID: PMC11153813 DOI: 10.3389/fvets.2024.1401392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Accepted: 04/30/2024] [Indexed: 06/09/2024] Open
Abstract
Salmonella enterica serovar Gallinarum (S. gallinarum) is an important host-specific pathogen that causes fowl typhoid, a severe systemic, septicemic, and fatal infection, in chickens. S. gallinarum causes high morbidity and mortality in chickens and poses a significant burden and economic losses to the poultry industry in many developing countries. However, the virulence factors and mechanisms of S. gallinarum-induced systemic infection in chickens remain poorly understood. In this study, we constructed a Salmonella pathogenicity island-14 (SPI-14) mutant strain (mSPI-14) of S. gallinarum and evaluated the pathogenicity of mSPI-14 in the chicken systemic infection model. The mSPI-14 exhibited the same level of bacterial growth and morphological characteristics but significantly reduced resistance to bile acids compared with the wild-type (WT) strain in vitro. The virulence of mSPI-14 was significantly attenuated in the chicken oral infection model in vivo. Chickens infected with WT showed typical clinical symptoms of fowl typhoid, with all birds succumbing to the infection within 6 to 9 days post-inoculation, and substantial increases in bacterial counts and significant pathological changes in the liver and spleen were observed. In contrast, all mSPI-14-infected chickens survived, the bacterial counts in the organs were significantly lower, and no significant pathological changes were observed in the liver and spleen. The expression of interleukin (IL)-1β, IL-12, CXCLi1, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in the liver of mSPI-14-infected chickens were significantly lower than those in the WT-infected chickens. These results indicate that SPI-14 is a crucial virulence factor in systemic infection of chickens, and avirulent mSPI-14 could be used to develop a new attenuated live vaccine to prevent S. gallinarum infection in chickens.
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Affiliation(s)
- Zuo Hu
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Shinjiro Ojima
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
- Research Center for Drug and Vaccine Development, National Institute of Infectious Diseases, Tokyo, Japan
| | - Zhihao Zhu
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Xiaoying Yu
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
- College of Veterinary Medicine, Southwest University, Chongqing, China
| | - Makoto Sugiyama
- Laboratory of Veterinary Anatomy, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Takeshi Haneda
- Laboratory of Microbiology, Kitasato University School of Pharmacy, Tokyo, Japan
| | - Masashi Okamura
- Section of Applied Veterinary Sciences, Division of Veterinary Sciences, Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan
| | - Hisaya K. Ono
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Dong-Liang Hu
- Department of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
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3
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Giraud E, Baucheron S, Foubert I, Doublet B, Nishino K, Cloeckaert A. Major primary bile salts repress Salmonella enterica serovar Typhimurium invasiveness partly via the efflux regulatory locus ramRA. Front Microbiol 2024; 15:1338261. [PMID: 38410385 PMCID: PMC10895713 DOI: 10.3389/fmicb.2024.1338261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Accepted: 01/29/2024] [Indexed: 02/28/2024] Open
Abstract
Bile represses Salmonella enterica serovar Typhimurium (S. Typhimurium) intestinal cell invasion, but it remains unclear which bile components and mechanisms are implicated. Previous studies reported that bile inhibits the RamR binding to the ramA promoter, resulting in ramA increased transcription, and that ramA overexpression is associated to decreased expression of type III secretion system 1 (TTSS-1) invasion genes and to impaired intestinal cell invasiveness in S. Typhimurium. In this study, we assessed the possible involvement of the ramRA multidrug efflux regulatory locus and individual bile salts in the bile-mediated repression of S. Typhimurium invasion, using Caco-2 intestinal epithelial cells and S. Typhimurium strain ATCC 14028s. Our results indicate that (i) major primary bile salts, chenodeoxycholate and its conjugated-derivative salts, cholate, and deoxycholate, activate ramA transcription in a RamR-dependent manner, and (ii) it results in repression of hilA, encoding the master activator of TTSS-1 genes, and as a consequence in the repression of cellular invasiveness. On the other hand, crude ox bile extract and cholate were also shown to repress the transcription of hilA independently of RamR, and to inhibit cell invasion independently of ramRA. Altogether, these data suggest that bile-mediated repression of S. Typhimurium invasion occurs through pleiotropic effects involving partly ramRA, as well as other unknown regulatory pathways. Bile components other than the bile salts used in this study might also participate in this phenomenon.
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Affiliation(s)
| | | | | | | | - Kunihiko Nishino
- Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
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Liu B, Jiang L, Liu Y, Sun H, Yan J, Kang C, Yang B. Enterohaemorrhagic E. coli utilizes host- and microbiota-derived L-malate as a signaling molecule for intestinal colonization. Nat Commun 2023; 14:7227. [PMID: 37945607 PMCID: PMC10636207 DOI: 10.1038/s41467-023-43149-7] [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: 09/11/2023] [Accepted: 11/01/2023] [Indexed: 11/12/2023] Open
Abstract
The mammalian gastrointestinal tract is a complex environment that hosts a diverse microbial community. To establish infection, bacterial pathogens must be able to compete with the indigenous microbiota for nutrients, as well as sense the host environment and modulate the expression of genes essential for colonization and virulence. Here, we found that enterohemorrhagic Escherichia coli (EHEC) O157:H7 imports host- and microbiota-derived L-malate using the DcuABC transporters and converts these substrates into fumarate to fuel anaerobic fumarate respiration during infection, thereby promoting its colonization of the host intestine. Moreover, L-malate is important not only for nutrient metabolism but also as a signaling molecule that activates virulence gene expression in EHEC O157:H7. The complete virulence-regulating pathway was elucidated; the DcuS/DcuR two-component system senses high L-malate levels and transduces the signal to the master virulence regulator Ler, which in turn activates locus of enterocyte effacement (LEE) genes to promote EHEC O157:H7 adherence to epithelial cells of the large intestine. Disruption of this virulence-regulating pathway by deleting either dcuS or dcuR significantly reduced colonization by EHEC O157:H7 in the infant rabbit intestinal tract; therefore, targeting these genes and altering physiological aspects of the intestinal environment may offer alternatives for EHEC infection treatment.
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Affiliation(s)
- Bin Liu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Lingyan Jiang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Yutao Liu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Hongmin Sun
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Jun Yan
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Chenbo Kang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China
| | - Bin Yang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, 300457, P. R. China.
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, 300071, P. R. China.
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5
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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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6
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Chowdhury R, Pavinski Bitar PD, Chapman HM, Altier C. Salmonella Invasion Is Controlled by Competition among Intestinal Chemical Signals. mBio 2023; 14:e0001223. [PMID: 37017539 PMCID: PMC10127606 DOI: 10.1128/mbio.00012-23] [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: 01/02/2023] [Accepted: 03/14/2023] [Indexed: 04/06/2023] Open
Abstract
The intestine is a complex, ever-changing environment replete with an array of signaling molecules. To colonize such a complex organ, pathogens have adapted to utilize specific cues from the local environment to intricately regulate the expression of their virulence determinants. Salmonella preferentially colonizes the distal ileum, a niche enriched in the metabolite formic acid. Here, we show that the relatively higher concentration of this metabolite in the distal ileum prevents other signals from repressing Salmonella invasion in that region. We show that imported and unmetabolized formic acid functions as a cytoplasmic signal that competitively binds to HilD, the master transcriptional regulator of Salmonella invasion, thus preventing repressive fatty acids from binding to the protein. This results in an increased lifetime of HilD and subsequent derepression of invasion genes. This study demonstrates an important mechanism by which Salmonella utilizes competition among signals in the gut to its advantage as a pathogen. IMPORTANCE Enteric pathogens acutely sense their environment for signals to regulate their virulence functions. We demonstrate here that the enteric pathogen Salmonella utilizes the competition among certain regional intestinal constituents to modulate its virulence determinants in that region. We show that the high concentration of formic acid in the ileum outcompetes other signals and triggers the activation of virulence genes in the ileum. This study shows a delicate spatial and temporal mechanism by which enteric pathogens may utilize the competition among environmental cues to optimize their pathogenicity.
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Affiliation(s)
- Rimi Chowdhury
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Paulina D. Pavinski Bitar
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Hanora M. Chapman
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
| | - Craig Altier
- Department of Population Medicine and Diagnostic Sciences, Cornell University, Ithaca, New York, USA
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7
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Ajingi YS, Rukying N, Jiddah NU, Koga Y, Jongruja N. Cloning, recombinant expression, purification, and functional characterization of AGAAN antibacterial peptide. 3 Biotech 2023; 13:88. [PMID: 36811032 PMCID: PMC9938847 DOI: 10.1007/s13205-023-03512-3] [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: 09/05/2022] [Accepted: 02/03/2023] [Indexed: 02/21/2023] Open
Abstract
A recombinant version of the AGAAN antimicrobial peptide (rAGAAN) was cloned, expressed, and purified in this study. Its antibacterial potency and stability in harsh environments were thoroughly investigated. A 15 kDa soluble rAGAAN was effectively expressed in E. coli. The purified rAGAAN exhibited a broad antibacterial spectrum and was efficacious against seven Gram-positive and Gram-negative bacteria. The minimal inhibitory concentration (MIC) of rAGAAN against the growth of M. luteus (TISTR 745) was as low as 60 µg/ml. Membrane permeation assay reveals that the integrity of the bacterial envelope is compromised. In addition, rAGAAN was resistant to temperature shock and maintained a high degree of stability throughout a reasonably extensive pH range. The bactericidal activity of rAGAAN ranged from 36.26 to 79.22% in the presence of pepsin and Bacillus proteases. Lower bile salt concentrations had no significant effect on the function of the peptide, whereas higher concentrations induced E. coli resistance. Additionally, rAGAAN exhibited minimal hemolytic activity against red blood cells. This study indicated that rAGAAN may be produced on a large scale in E. coli and that it had an excellent antibacterial activity and sufficient stability. This first work to express biologically active rAGAAN in E. coli yielded 8.01 mg/ml at 16 °C/150 rpm for 18 h in Luria Bertani (LB) medium supplemented with 1% glucose and induced with 0.5 mM IPTG. It also assesses the interfering factors that influence the activity of the peptide, demonstrating its potential for research and therapy of multidrug-resistant bacterial infections.
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Affiliation(s)
- Ya’u Sabo Ajingi
- Department of Microbiology, Faculty of Science, King Mongkut’s University of Technology (KMUTT), 126 Pracha Uthit Rd., Bang Mod, Thung Khru, Thonburi , 10140 Bangkok Thailand
- Department of Biology, Faculty of Science, Kano University of Science and Technology (KUST), Wudil, Nigeria
| | - Neeranuch Rukying
- Department of Microbiology, Faculty of Science, King Mongkut’s University of Technology (KMUTT), 126 Pracha Uthit Rd., Bang Mod, Thung Khru, Thonburi , 10140 Bangkok Thailand
| | - Nafiu Usman Jiddah
- Department of Microbiology, Faculty of Science, King Mongkut’s University of Technology (KMUTT), 126 Pracha Uthit Rd., Bang Mod, Thung Khru, Thonburi , 10140 Bangkok Thailand
- Department of Biochemistry, Faculty of Science, Gombe State University, Gombe, Nigeria
| | - Yuichi Koga
- Department of Applied Chemistry, Faculty of Engineering, Okayama University of Science , Ridai-cho 1-1, Kita-ku, Okayama City, Okayama Japan
| | - Nujarin Jongruja
- Department of Microbiology, Faculty of Science, King Mongkut’s University of Technology (KMUTT), 126 Pracha Uthit Rd., Bang Mod, Thung Khru, Thonburi , 10140 Bangkok Thailand
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Malarney KP, Chang PV. Chemoproteomic Approaches for Unraveling Prokaryotic Biology. Isr J Chem 2023; 63:e202200076. [PMID: 37842282 PMCID: PMC10575470 DOI: 10.1002/ijch.202200076] [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: 09/28/2022] [Indexed: 03/07/2023]
Abstract
Bacteria are ubiquitous lifeforms with important roles in the environment, biotechnology, and human health. Many of the functions that bacteria perform are mediated by proteins and enzymes, which catalyze metabolic transformations of small molecules and modifications of proteins. To better understand these biological processes, chemical proteomic approaches, including activity-based protein profiling, have been developed to interrogate protein function and enzymatic activity in physiologically relevant contexts. Here, chemoproteomic strategies and technological advances for studying bacterial physiology, pathogenesis, and metabolism are discussed. The development of chemoproteomic approaches for characterizing protein function and enzymatic activity within bacteria remains an active area of research, and continued innovations are expected to provide breakthroughs in understanding bacterial biology.
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Affiliation(s)
- Kien P Malarney
- Department of Microbiology, Cornell University, Ithaca, NY 14853 (USA)
| | - Pamela V Chang
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY 14853 (USA)
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853 (USA)
- Cornell Center for Immunology, Cornell University, Ithaca, NY 14853 (USA)
- Cornell Institute of Host-Microbe Interactions and Disease, Cornell University, Ithaca, NY 14853 (USA)
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9
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Larabi AB, Masson HLP, Bäumler AJ. Bile acids as modulators of gut microbiota composition and function. Gut Microbes 2023; 15:2172671. [PMID: 36740850 PMCID: PMC9904317 DOI: 10.1080/19490976.2023.2172671] [Citation(s) in RCA: 40] [Impact Index Per Article: 40.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Accepted: 01/16/2023] [Indexed: 02/07/2023] Open
Abstract
Changes in the composition of gut-associated microbial communities are associated with many human illnesses, but the factors driving dysbiosis remain incompletely understood. One factor governing the microbiota composition in the gut is bile. Bile acids shape the microbiota composition through their antimicrobial activity and by activating host signaling pathways that maintain gut homeostasis. Although bile acids are host-derived, their functions are integrally linked to bacterial metabolism, which shapes the composition of the intestinal bile acid pool. Conditions that change the size or composition of the bile acid pool can trigger alterations in the microbiota composition that exacerbate inflammation or favor infection with opportunistic pathogens. Therefore, manipulating the composition or size of the bile acid pool might be a promising strategy to remediate dysbiosis.
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Affiliation(s)
- Anaïs B. Larabi
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, CA, USA
| | - Hugo L. P. Masson
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, CA, USA
| | - Andreas J. Bäumler
- Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, Davis, CA, USA
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10
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Yang X, Stein KR, Hang HC. Anti-infective bile acids bind and inactivate a Salmonella virulence regulator. Nat Chem Biol 2023; 19:91-100. [PMID: 36175659 PMCID: PMC9805502 DOI: 10.1038/s41589-022-01122-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 07/26/2022] [Indexed: 01/03/2023]
Abstract
Bile acids are prominent host and microbiota metabolites that modulate host immunity and microbial pathogenesis. However, the mechanisms by which bile acids suppress microbial virulence are not clear. To identify the direct protein targets of bile acids in bacterial pathogens, we performed activity-guided chemical proteomic studies. In Salmonella enterica serovar Typhimurium, chenodeoxycholic acid (CDCA) most effectively inhibited the expression of virulence genes and invasion of epithelial cells and interacted with many proteins. Notably, we discovered that CDCA can directly bind and inhibit the function of HilD, an important transcriptional regulator of S. Typhimurium virulence and pathogenesis. Our characterization of bile acid-resistant HilD mutants in vitro and in S. Typhimurium infection models suggests that HilD is one of the key protein targets of anti-infective bile acids. This study highlights the utility of chemical proteomics to identify the direct protein targets of microbiota metabolites for mechanistic studies in bacterial pathogens.
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Affiliation(s)
- Xinglin Yang
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA, USA
| | - Kathryn R Stein
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA, USA
| | - Howard C Hang
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA, USA.
- Department of Chemistry, Scripps Research, La Jolla, CA, USA.
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11
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Zhao X, Yang X, Hang HC. Chemoproteomic Analysis of Microbiota Metabolite-Protein Targets and Mechanisms. Biochemistry 2022; 61:2822-2834. [PMID: 34989554 PMCID: PMC9256862 DOI: 10.1021/acs.biochem.1c00758] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The microbiota have emerged as an important factor in host physiology, disease, and response to therapy. These diverse microbes (bacteria, virus, fungi, and protists) encode unique functions and metabolites that regulate intraspecies and interspecies interactions. While the mechanisms of some microbiota species and metabolites have been elucidated, the diversity and abundance of different microbiota species and their associated pathways suggest many more metabolites and mechanisms of action remain to be discovered. In this Perspective, we highlight how the advances in chemical proteomics have provided new opportunities to elucidate the molecular targets of specific microbiota metabolites and reveal new mechanisms of action. The continued development of specific microbiota metabolite reporters and more precise proteomic methods should reveal new microbiota mechanisms of action, therapeutic targets, and biomarkers for a variety of human diseases.
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12
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Gautier T, Olivieiro N, Ferron S, Le Pogam P, David-Le Gall S, Sauvager A, Leroyer P, Cannie I, Dion S, Sweidan A, Loréal O, Tomasi S, Bousarghin L. Bacteroides fragilis derived metabolites, identified by molecular networking, decrease Salmonella virulence in mice model. Front Microbiol 2022; 13:1023315. [DOI: 10.3389/fmicb.2022.1023315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 10/26/2022] [Indexed: 11/12/2022] Open
Abstract
In the gut microbiota, resident bacteria prevent pathogens infection by producing specific metabolites. Among bacteria belonging to phylum Bacteroidota, we have previously shown that Bacteroides fragilis or its cell-free supernatant inhibited in vitro Salmonella Heidelberg translocation. In the present study, we have analyzed this supernatant to identify bioactive molecules after extraction and subsequent fractionation using a semi-preparative reversed-phase Liquid Chromatography High-Resolution Tandem Mass Spectrometry (LC-HRMS/MS). The results indicated that only two fractions (F3 and F4) strongly inhibited S. Heidelberg translocation in a model mimicking the intestinal epithelium. The efficiency of the bioactive fractions was evaluated in BALB/c mice, and the results showed a decrease of S. Heidelberg in Peyer’s patches and spleen, associated with a decrease in inflammatory cytokines and neutrophils infiltration. The reduction of the genus Alistipes in mice receiving the fractions could be related to the anti-inflammatory effects of bioactive fractions. Furthermore, these bioactive fractions did not alter the gut microbiota diversity in mice. To further characterize the compounds present in these bioactive fractions, Liquid Chromatography High-Resolution Tandem Mass Spectrometry (LC-HRMS/MS) data were analyzed through molecular networking, highlighting cholic acid (CA) and deoxycholic acid. In vitro, CA had inhibitory activity against the translocation of S. Heidelberg by significantly decreasing the expression of Salmonella virulence genes such as sipA. The bioactive fractions also significantly downregulated the flagellar gene fliC, suggesting the involvement of other active molecules. This study showed the interest to characterize better the metabolites produced by B. fragilis to make them means of fighting pathogenic bacteria by targeting their virulence factor without modifying the gut microbiota.
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Autoinducer-2 and bile salts induce c-di-GMP synthesis to repress the T3SS via a T3SS chaperone. Nat Commun 2022; 13:6684. [PMID: 36335118 PMCID: PMC9637222 DOI: 10.1038/s41467-022-34607-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 10/31/2022] [Indexed: 11/07/2022] Open
Abstract
Cyclic di-GMP (c-di-GMP) transduces extracellular stimuli into intracellular responses, coordinating a plethora of important biological processes. Low levels of c-di-GMP are often associated with highly virulent behavior that depends on the type III secretion system (T3SS) effectors encoded, whereas elevated levels of c-di-GMP lead to the repression of T3SSs. However, extracellular signals that modulate c-di-GMP metabolism to control T3SSs and c-di-GMP effectors that relay environmental stimuli to changes in T3SS activity remain largely obscure. Here, we show that the quorum sensing signal autoinducer-2 (AI-2) induces c-di-GMP synthesis via a GAPES1 domain-containing diguanylate cyclase (DGC) YeaJ to repress T3SS-1 gene expression in Salmonella enterica serovar Typhimurium. YeaJ homologs capable of sensing AI-2 are present in many other species belonging to Enterobacterales. We also reveal that taurocholate and taurodeoxycholate bind to the sensory domain of the DGC YedQ to induce intracellular accumulation of c-di-GMP, thus repressing the expression of T3SS-1 genes. Further, we find that c-di-GMP negatively controls the function of T3SSs through binding to the widely conserved CesD/SycD/LcrH family of T3SS chaperones. Our results support a model in which bacteria sense changes in population density and host-derived cues to regulate c-di-GMP synthesis, thereby modulating the activity of T3SSs via a c-di-GMP-responsive T3SS chaperone.
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14
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Rogers AR, Turner EE, Johnson DT, Ellermeier JR. Envelope Stress Activates Expression of the Twin Arginine Translocation (Tat) System in Salmonella. Microbiol Spectr 2022; 10:e0162122. [PMID: 36036643 PMCID: PMC9604234 DOI: 10.1128/spectrum.01621-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/16/2022] [Indexed: 12/31/2022] Open
Abstract
The twin arginine translocation system (Tat) is a protein export system that is conserved in bacteria, archaea, and plants. In Gram-negative bacteria, it is required for the export of folded proteins from the cytoplasm to the periplasm. In Salmonella, there are 30 proteins that are predicted substrates of Tat, and among these are enzymes required for anaerobic respiration and peptidoglycan remodeling. We have demonstrated that some conditions that induce bacterial envelope stress activate expression of a ΔtatABC-lacZ fusion in Salmonella enterica serovar Typhimurium. Particularly, the addition of bile salts to the growth medium causes a 3-fold induction of a ΔtatABC-lacZ reporter fusion. Our data demonstrate that this induction is mediated via the phage shock protein (Psp) stress response system protein PspA. Further, we show that deletion of tatABC increases the induction of tatABC expression in bile salts. Indeed, the data suggest significant interaction between PspA and the Tat system in the regulatory response to bile salts. Although we have not identified the precise mechanism of Psp regulation of tatABC, our work shows that PspA is involved in the activation of tatABC expression by bile salts and adds another layer of complexity to the Salmonella response to envelope stress. IMPORTANCE Salmonella species cause an array of diseases in a variety of hosts. This research is significant in showing induction of the Tat system as a defense against periplasmic stress. Understanding the underlying mechanism of this regulation broadens our understanding of the Salmonella stress response, which is critical to the ability of the organism to cause infection.
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Affiliation(s)
- Alexandra R. Rogers
- Department of Microbiology and Immunology, Midwestern University, Glendale, Arizona, USA
| | - Ezekeial E. Turner
- College of Graduate Studies, Midwestern University, Glendale, Arizona, USA
| | - Deauna T. Johnson
- Department of Microbiology and Immunology, Midwestern University, Glendale, Arizona, USA
| | - Jeremy R. Ellermeier
- Department of Microbiology and Immunology, Midwestern University, Glendale, Arizona, USA
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15
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Chowdhury R, Pavinski Bitar PD, Adams MC, Chappie JS, Altier C. AraC-type regulators HilC and RtsA are directly controlled by an intestinal fatty acid to regulate Salmonella invasion. Mol Microbiol 2021; 116:1464-1475. [PMID: 34687258 DOI: 10.1111/mmi.14835] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/18/2021] [Accepted: 10/18/2021] [Indexed: 01/30/2023]
Abstract
Invasion of the intestinal epithelium is an essential but energetically expensive survival strategy and is, therefore, tightly regulated by using specific cues from the environment. The enteric pathogen Salmonella controls its invasion machinery through the elegant coordination of three AraC-type transcription activators, HilD, HilC, and RtsA. Most environmental signals target HilD to control invasion, whereas HilC and RtsA are known only to augment these effects on HilD. Here we show that a fatty acid found in the murine colon, cis-2-hexadecenoic acid (c2-HDA), represses Salmonella invasion by directly targeting HilC and RtsA, in addition to HilD. c2-HDA directly binds each of these regulators and inhibits their attachment to DNA targets, repressing invasion even in the absence of HilD. Fatty acid binding, however, does not affect HilC and RtsA protein stability, unlike HilD. Importantly, we show that HilC and RtsA are highly effective in restoring HilD production and invasion gene expression after elimination of the repressive fatty acid c2-HDA. Together, these results illuminate a precise mechanism by which HilC and RtsA may modulate invasion as Salmonella navigates through different regions of the intestine, contributing to our understanding of how this enteric pathogen senses and adapts to a diverse intestinal environment while maintaining its virulence.
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Affiliation(s)
- Rimi Chowdhury
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Paulina D Pavinski Bitar
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
| | - Myfanwy C Adams
- Department of Molecular Medicine, Cornell University, Ithaca, New York, USA
| | - Joshua S Chappie
- Department of Molecular Medicine, Cornell University, Ithaca, New York, USA
| | - Craig Altier
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, USA
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16
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Aguirre AM, Yalcinkaya N, Wu Q, Swennes A, Tessier ME, Roberts P, Miyajima F, Savidge T, Sorg JA. Bile acid-independent protection against Clostridioides difficile infection. PLoS Pathog 2021; 17:e1010015. [PMID: 34665847 PMCID: PMC8555850 DOI: 10.1371/journal.ppat.1010015] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Revised: 10/29/2021] [Accepted: 10/07/2021] [Indexed: 12/21/2022] Open
Abstract
Clostridioides difficile infections occur upon ecological / metabolic disruptions to the normal colonic microbiota, commonly due to broad-spectrum antibiotic use. Metabolism of bile acids through a 7α-dehydroxylation pathway found in select members of the healthy microbiota is regarded to be the protective mechanism by which C. difficile is excluded. These 7α-dehydroxylated secondary bile acids are highly toxic to C. difficile vegetative growth, and antibiotic treatment abolishes the bacteria that perform this metabolism. However, the data that supports the hypothesis that secondary bile acids protect against C. difficile infection is supported only by in vitro data and correlative studies. Here we show that bacteria that 7α-dehydroxylate primary bile acids protect against C. difficile infection in a bile acid-independent manner. We monoassociated germ-free, wildtype or Cyp8b1-/- (cholic acid-deficient) mutant mice and infected them with C. difficile spores. We show that 7α-dehydroxylation (i.e., secondary bile acid generation) is dispensable for protection against C. difficile infection and provide evidence that Stickland metabolism by these organisms consumes nutrients essential for C. difficile growth. Our findings indicate secondary bile acid production by the microbiome is a useful biomarker for a C. difficile-resistant environment but the microbiome protects against C. difficile infection in bile acid-independent mechanisms. Secondary bile acid production by the colonic microbiome strongly correlates with an environment that is resistant to C. difficile invasion. However, it remained unclear if these bile acids provided in vivo protection. Here, we show that members of the microbiome that generate secondary bile acids (e.g., C. scindens) protect against C. difficile disease independently of secondary bile acid generation. These results are important because efforts to restore colonization resistance (e.g., FMT or precision bacterial therapy) focus on restoring secondary bile acid generation. Instead, restoring the organisms that produce 5-aminovalerate or consume proline / glycine are more important.
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Affiliation(s)
- Andrea Martinez Aguirre
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
| | - Nazli Yalcinkaya
- Baylor College of Medicine & Texas Children’s Hospital, Houston, Texas, United States of America
| | - Qinglong Wu
- Baylor College of Medicine & Texas Children’s Hospital, Houston, Texas, United States of America
| | - Alton Swennes
- Baylor College of Medicine & Texas Children’s Hospital, Houston, Texas, United States of America
| | - Mary Elizabeth Tessier
- Baylor College of Medicine & Texas Children’s Hospital, Houston, Texas, United States of America
| | - Paul Roberts
- Royal Liverpool and Broadgreen University Hospitals NHS Trust, Liverpool, United Kingdom
| | - Fabio Miyajima
- Royal Liverpool and Broadgreen University Hospitals NHS Trust, Liverpool, United Kingdom
- Oswaldo Cruz Foundation, Ceara branch, Fortaleza, Brazil
| | - Tor Savidge
- Baylor College of Medicine & Texas Children’s Hospital, Houston, Texas, United States of America
| | - Joseph A. Sorg
- Department of Biology, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
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17
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Pérez-Morales D, Nava-Galeana J, Rosales-Reyes R, Teehan P, Yakhnin H, Melchy-Pérez EI, Rosenstein Y, De la Cruz MA, Babitzke P, Bustamante VH. An incoherent feedforward loop formed by SirA/BarA, HilE and HilD is involved in controlling the growth cost of virulence factor expression by Salmonella Typhimurium. PLoS Pathog 2021; 17:e1009630. [PMID: 34048498 PMCID: PMC8192010 DOI: 10.1371/journal.ppat.1009630] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 06/10/2021] [Accepted: 05/10/2021] [Indexed: 12/02/2022] Open
Abstract
An intricate regulatory network controls the expression of Salmonella virulence genes. The transcriptional regulator HilD plays a central role in this network by controlling the expression of tens of genes mainly required for intestinal colonization. Accordingly, the expression/activity of HilD is highly regulated by multiple factors, such as the SirA/BarA two-component system and the Hcp-like protein HilE. SirA/BarA positively regulates translation of hilD mRNA through a regulatory cascade involving the small RNAs CsrB and CsrC, and the RNA-binding protein CsrA, whereas HilE inhibits HilD activity by protein-protein interaction. In this study, we show that SirA/BarA also positively regulates translation of hilE mRNA through the same mentioned regulatory cascade. Thus, our results reveal a paradoxical regulation exerted by SirA/BarA-Csr on HilD, which involves simultaneous opposite effects, direct positive control and indirect negative control through HilE. This kind of regulation is called an incoherent type-1 feedforward loop (I1-FFL), which is a motif present in certain regulatory networks and represents a complex biological problem to decipher. Interestingly, our results, together with those from a previous study, indicate that HilE, the repressor component of the I1-FFL reported here (I1-FFLSirA/BarA-HilE-HilD), is required to reduce the growth cost imposed by the expression of the genes regulated by HilD. Moreover, we and others found that HilE is necessary for successful intestinal colonization by Salmonella. Thus, these findings support that I1-FFLSirA/BarA-HilE-HilD cooperates to control the precise amount and activity of HilD, for an appropriate balance between the growth cost and the virulence benefit generated by the expression of the genes induced by this regulator. I1-FFLSirA/BarA-HilE-HilD represents a complex regulatory I1-FFL that involves multiple regulators acting at distinct levels of gene expression, as well as showing different connections to the rest of the regulatory network governing Salmonella virulence. To infect the intestine of a broad range of hosts, including humans, Salmonella is required to express a large number of genes encoding different cellular functions, which imposes a growth penalty. Thus, Salmonella has developed complex regulatory mechanisms that control the expression of virulence genes. Here we identified a novel and sophisticated regulatory mechanism that is involved in the fine-tuned control of the expression level and activity of the transcriptional regulator HilD, for the appropriate balance between the growth cost and the virulence benefit generated by the expression of tens of Salmonella genes. This mechanism forms an incoherent type-1 feedforward loop (I1-FFL), which involves paradoxical regulation; that is, a regulatory factor exerting simultaneous opposite control (positive and negative) on another factor. I1-FFLs are present in regulatory networks of diverse organisms, from bacteria to humans, and represent a complex biological problem to decipher. Interestingly, the I1-FFL reported here is integrated by ancestral regulators and by regulators that Salmonella has acquired during evolution. Thus, our findings reveal a novel I1-FFL of bacteria, which is involved in virulence. Moreover, our results illustrate the integration of ancestral and acquired factors into a regulatory motif, which can lead to the expansion of regulatory networks.
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Affiliation(s)
- Deyanira Pérez-Morales
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- Consejo Nacional de Ciencia y Tecnología, Ciudad de México, México
| | - Jessica Nava-Galeana
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Roberto Rosales-Reyes
- Unidad de Investigación en Medicina Experimental, Facultad de Medicina, Universidad Nacional Autónoma de México, Ciudad de México, México
| | - Paige Teehan
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Helen Yakhnin
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Erika I. Melchy-Pérez
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Yvonne Rosenstein
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
| | - Miguel A. De la Cruz
- Unidad de Investigación Médica en Enfermedades Infecciosas y Parasitarias, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, Ciudad de México, México
| | - Paul Babitzke
- Department of Biochemistry and Molecular Biology, Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Víctor H. Bustamante
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, México
- * E-mail:
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18
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Chowdhury R, Pavinski Bitar PD, Keresztes I, Condo AM, Altier C. A diffusible signal factor of the intestine dictates Salmonella invasion through its direct control of the virulence activator HilD. PLoS Pathog 2021; 17:e1009357. [PMID: 33617591 PMCID: PMC7932555 DOI: 10.1371/journal.ppat.1009357] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Revised: 03/04/2021] [Accepted: 02/02/2021] [Indexed: 12/16/2022] Open
Abstract
Successful intestinal infection by Salmonella requires optimized invasion of the gut epithelium, a function that is energetically costly. Salmonella have therefore evolved to intricately regulate the expression of their virulence determinants by utilizing specific environmental cues. Here we show that a powerful repressor of Salmonella invasion, a cis-2 unsaturated long chain fatty acid, is present in the murine large intestine. Originally identified in Xylella fastidiosa as a diffusible signal factor for quorum sensing, this fatty acid directly interacts with HilD, the master transcriptional regulator of Salmonella, and prevents hilA activation, thus inhibiting Salmonella invasion. We further identify the fatty acid binding region of HilD and show it to be selective and biased in favour of signal factors with a cis-2 unsaturation over other intestinal fatty acids. Single mutation of specific HilD amino acids to alanine prevented fatty acid binding, thereby alleviating their repressive effect on invasion. Together, these results highlight an exceedingly sensitive mechanism used by Salmonella to colonize its host by detecting and exploiting specific molecules present within the complex intestinal environment.
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Affiliation(s)
- Rimi Chowdhury
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- * E-mail: (RC); (CA)
| | - Paulina D. Pavinski Bitar
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
| | - Ivan Keresztes
- Chemistry NMR Facility, Cornell University, Ithaca, New York, United States of America
| | - Anthony M. Condo
- Chemistry NMR Facility, Cornell University, Ithaca, New York, United States of America
| | - Craig Altier
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, United States of America
- * E-mail: (RC); (CA)
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19
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Gadishaw-Lue C, Banaag A, Birstonas S, Francis AS, Barnett Foster D. Bile Salts Differentially Enhance Resistance of Enterohemorrhagic Escherichia coli O157:H7 to Host Defense Peptides. Infect Immun 2021; 89:e00719-20. [PMID: 33229368 PMCID: PMC7822141 DOI: 10.1128/iai.00719-20] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 11/13/2020] [Indexed: 12/28/2022] Open
Abstract
During passage through the human gastrointestinal tract, enterohemorrhagic Escherichia coli (EHEC) is exposed to membrane-damaging bile in the small intestine. We previously reported that EHEC treatment with a physiological bile salt mixture upregulates basRS, encoding a two-component system, and arnBCADTEF, encoding the aminoarabinose lipid A modification pathway (J. V. Kus, A. Gebremedhin, V. Dang, S. L. Tran, A. Serbanescu, and D. Barnett Foster, J Bacteriol 193: 4509-4515, 2011, https://doi.org/10.1128/JB.00200-11). The present study examined the effect of bile salt mix (BSM) treatment on EHEC resistance to three human gastrointestinal defense peptides-HD-5, HNP-1, and LL-37-as well as the role of basRS and arnT in the respective responses. After BSM treatment, EHEC resistance to HD-5 and HNP-1 was significantly increased in a BSM-, defensin dose-dependent manner. The resistance phenotype was dependent on both basRS and arnT However, the BSM treatment did not alter EHEC resistance to LL-37, even when the ompT gene, encoding an LL-37 cleavage protease, was disrupted. Interestingly, enteropathogenic E. coli, a related pathogen that infects the small intestine, showed a similar BSM-induced resistance phenotype. Using a model of EHEC infection in Galleria mellonella, we found significantly lower survival rates in wax moth larvae infected with BSM-treated wild-type EHEC than in those infected with a BSM-treated basS mutant, suggesting that treatment with a physiological BSM enhances virulence through a basS-mediated pathway. The results of this investigation provide persuasive evidence that bile salts typically encountered during transit through the small intestine can serve as an environmental cue for EHEC, enhancing resistance to several key host defense peptides.
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Affiliation(s)
- Crystal Gadishaw-Lue
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada
| | - Alyssa Banaag
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada
| | - Sarah Birstonas
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada
| | - Aju-Sue Francis
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada
| | - Debora Barnett Foster
- Department of Chemistry and Biology, Ryerson University, Toronto, Ontario, Canada
- Faculty of Dentistry, University of Toronto, Toronto, Ontario, Canada
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20
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Diffusible Signal Factors Act through AraC-Type Transcriptional Regulators as Chemical Cues To Repress Virulence of Enteric Pathogens. Infect Immun 2020; 88:IAI.00226-20. [PMID: 32690633 PMCID: PMC7504960 DOI: 10.1128/iai.00226-20] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 07/08/2020] [Indexed: 01/02/2023] Open
Abstract
Successful colonization by enteric pathogens is contingent upon effective interactions with the host and the resident microbiota. These pathogens thus respond to and integrate myriad signals to control virulence. Long-chain fatty acids repress the virulence of the important enteric pathogens Salmonella enterica and Vibrio cholerae by repressing AraC-type transcriptional regulators in pathogenicity islands. While several fatty acids are known to be repressive, we show here that cis-2-unsaturated fatty acids, a rare chemical class used as diffusible signal factors (DSFs), are highly potent inhibitors of virulence functions. We found that DSFs repressed virulence gene expression of enteric pathogens by interacting with transcriptional regulators of the AraC family. In Salmonella enterica serovar Typhimurium, DSFs repress the activity of HilD, an AraC-type activator essential to the induction of epithelial cell invasion, by both preventing its interaction with target DNA and inducing its rapid degradation by Lon protease. cis-2-Hexadecenoic acid (c2-HDA), a DSF produced by Xylella fastidiosa, was the most potent among those tested, repressing the HilD-dependent transcriptional regulator hilA and the type III secretion effector sopB >200- and 68-fold, respectively. Further, c2-HDA attenuated the transcription of the ToxT-dependent cholera toxin synthesis genes of V. cholerae c2-HDA significantly repressed invasion gene expression by Salmonella in the murine colitis model, indicating that the HilD-dependent signaling pathway functions within the complex milieu of the animal intestine. These data argue that enteric pathogens respond to DSFs as interspecies signals to identify appropriate niches in the gut for virulence activation, which could be exploited to control the virulence of enteric pathogens.
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21
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Staes I, Passaris I, Cambré A, Aertsen A. Population heterogeneity tactics as driving force in Salmonella virulence and survival. Food Res Int 2019; 125:108560. [DOI: 10.1016/j.foodres.2019.108560] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 07/05/2019] [Accepted: 07/12/2019] [Indexed: 01/28/2023]
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22
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HilD induces expression of a novel Salmonella Typhimurium invasion factor, YobH, through a regulatory cascade involving SprB. Sci Rep 2019; 9:12725. [PMID: 31484980 PMCID: PMC6726612 DOI: 10.1038/s41598-019-49192-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Accepted: 08/20/2019] [Indexed: 12/27/2022] Open
Abstract
HilD is an AraC-like transcriptional regulator encoded in the Salmonella pathogenicity island 1 (SPI-1), which actives transcription of many genes within and outside SPI-1 that are mainly required for invasion of Salmonella into host cells. HilD controls expression of target genes directly or by acting through distinct regulators; three different regulatory cascades headed by HilD have been described to date. Here, by analyzing the effect of HilD on the yobH gene in Salmonella enterica serovar Typhimurium (S. Typhimurium), we further define an additional regulatory cascade mediated by HilD, which was revealed by previous genome-wide analyses. In this regulatory cascade, HilD acts through SprB, a LuxR-like regulator encoded in SPI-1, to induce expression of virulence genes. Our data show that HilD induces expression of sprB by directly counteracting H-NS-mediated repression on the promoter region upstream of this gene. Then, SprB directly activates expression of several genes including yobH, slrP and ugtL. Interestingly, we found that YobH, a protein of only 79 amino acids, is required for invasion of S. Typhimurium into HeLa cells and mouse macrophages. Thus, our results reveal a novel S. Typhimurium invasion factor and provide more evidence supporting the HilD-SprB regulatory cascade.
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23
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Ducarmon QR, Zwittink RD, Hornung BVH, van Schaik W, Young VB, Kuijper EJ. Gut Microbiota and Colonization Resistance against Bacterial Enteric Infection. Microbiol Mol Biol Rev 2019; 83:e00007-19. [PMID: 31167904 PMCID: PMC6710460 DOI: 10.1128/mmbr.00007-19] [Citation(s) in RCA: 241] [Impact Index Per Article: 48.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The gut microbiome is critical in providing resistance against colonization by exogenous microorganisms. The mechanisms via which the gut microbiota provide colonization resistance (CR) have not been fully elucidated, but they include secretion of antimicrobial products, nutrient competition, support of gut barrier integrity, and bacteriophage deployment. However, bacterial enteric infections are an important cause of disease globally, indicating that microbiota-mediated CR can be disturbed and become ineffective. Changes in microbiota composition, and potential subsequent disruption of CR, can be caused by various drugs, such as antibiotics, proton pump inhibitors, antidiabetics, and antipsychotics, thereby providing opportunities for exogenous pathogens to colonize the gut and ultimately cause infection. In addition, the most prevalent bacterial enteropathogens, including Clostridioides difficile, Salmonella enterica serovar Typhimurium, enterohemorrhagic Escherichia coli, Shigella flexneri, Campylobacter jejuni, Vibrio cholerae, Yersinia enterocolitica, and Listeria monocytogenes, can employ a wide array of mechanisms to overcome colonization resistance. This review aims to summarize current knowledge on how the gut microbiota can mediate colonization resistance against bacterial enteric infection and on how bacterial enteropathogens can overcome this resistance.
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Affiliation(s)
- Q R Ducarmon
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - R D Zwittink
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - B V H Hornung
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
| | - W van Schaik
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
| | - V B Young
- Department of Microbiology and Immunology, University of Michigan, Ann Arbor, Michigan, USA
- Department of Internal Medicine/Infectious Diseases Division, University of Michigan Medical Center, Ann Arbor, Michigan, USA
| | - E J Kuijper
- Center for Microbiome Analyses and Therapeutics, Leiden University Medical Center, Leiden, Netherlands
- Experimental Bacteriology, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Clinical Microbiology Laboratory, Department of Medical Microbiology, Leiden University Medical Center, Leiden, Netherlands
- Netherlands Donor Feces Bank, Leiden, Netherlands
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24
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PhoP-Mediated Repression of the SPI1 Type 3 Secretion System in Salmonella enterica Serovar Typhimurium. J Bacteriol 2019; 201:JB.00264-19. [PMID: 31182495 DOI: 10.1128/jb.00264-19] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Accepted: 05/31/2019] [Indexed: 12/13/2022] Open
Abstract
Salmonella must rapidly adapt to various niches in the host during infection. Relevant virulence factors must be appropriately induced, and systems that are detrimental in a particular environment must be turned off. Salmonella infects intestinal epithelial cells using a type 3 secretion system (T3SS) encoded on Salmonella pathogenicity island 1 (SPI1). The system is controlled by three AraC-like regulators, HilD, HilC, and RtsA, which form a complex feed-forward loop to activate expression of hilA, encoding the main transcriptional regulator of T3SS structural genes. This system is tightly regulated, with many of the activating signals acting at the level of hilD translation or HilD protein activity. Once inside the phagosomes of epithelial cells, or in macrophages during systemic stages of disease, the SPI1 T3SS is no longer required or expressed. Here, we show that the PhoPQ two-component system, critical for intracellular survival, appears to be the primary mechanism by which Salmonella shuts down the SPI1 T3SS. PhoP negatively regulates hilA through multiple distinct mechanisms: direct transcriptional repression of the hilA promoter, indirect transcriptional repression of both the hilD and rtsA promoters, and activation of the small RNA (sRNA) PinT. Genetic analyses and electrophoretic mobility shift assays suggest that PhoP specifically binds the hilA promoter to block binding of activators HilD, HilC, and RtsA as a mechanism of repression.IMPORTANCE Salmonella is one of the most common foodborne pathogens, causing an estimated 1.2 million illnesses per year in the United States. A key step in infection is the activation of the bacterial invasion machinery, which induces uptake of the bacterium into epithelial cells and leads to induction of inflammatory diarrhea. Upon entering the vacuolar compartments of host cells, Salmonella senses an environmental transition and represses the invasion machinery with a two-component system relevant for survival within the vacuole. This adaptation to specific host niches is an important example of how signals are integrated for survival of the pathogen.
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Bellido-Carreras N, Argüello H, Zaldívar-López S, Jiménez-Marín Á, Martins RP, Arce C, Morera L, Carvajal A, Garrido JJ. Salmonella Typhimurium Infection Along the Porcine Gastrointestinal Tract and Associated Lymphoid Tissues. Vet Pathol 2019; 56:681-690. [PMID: 31106677 DOI: 10.1177/0300985819843682] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Salmonella is a major foodborne pathogen and pork is one of the main sources of human salmonellosis. Understanding the pathogenesis and progression of the infection within the host is of interest to establish potential approaches to control the disease in pigs. The present study evaluates factors such as intestinal colonization, fecal shedding, and pathogen persistence by 2 studies using experimental challenge with Salmonella Typhimurium in weaned pigs and euthanasia at different time points (1, 2, and 6 and 2, 14, and 30 days postinfection [dpi], respectively). Histopathology of intestine at early time points (1 dpi and 2 dpi) showed severe damage to the epithelium together with an increase in polymorphonuclear cells and macrophages (P < .001), particularly in jejunum and ileum. Large quantities of Salmonella were detected within the contents of the ileum, cecum, and colon in early infection. Salmonella could also be observed in the medulla of tonsils and mesenteric lymph nodes. From 6 dpi onward, signs of recovery were observed, with progressive restoration of the epithelium, reduction of the inflammatory infiltrate, and elimination of Salmonella from the mucosa. Concentration of Salmonella in feces and ileum content decreased, but shedding did not cease even at 4 weeks after infection. Persistence of the bacteria in mesenteric lymph nodes was identified within the connective tissue at 14 and 30 dpi. Our results demonstrate a recovery of the disease after an initial acute phase but also show persistence within the lumen and surrounding lymphoid tissue. These findings are relevant to developing effective control strategies.
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Affiliation(s)
- Natividad Bellido-Carreras
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
| | - Héctor Argüello
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
| | - Sara Zaldívar-López
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
| | - Ángeles Jiménez-Marín
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
| | - Rodrigo P Martins
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain.,2 Cibles Thérapeutiques, Institut National de la Santé et de la Recherche Médicale UMR1162, Institut de Génétique Moléculaire, Louis, Paris, France
| | - Cristina Arce
- 3 Departamento de Producción Animal, Facultad de Veterinaria, Universidad de Córdoba, Córdoba, Spain
| | - Luis Morera
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
| | - Ana Carvajal
- 4 Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, León, Spain
| | - Juan J Garrido
- 1 Departamento de Genética, Facultad de Veterinaria, Grupo de Genómica y Mejora Animal, Universidad de Córdoba, Córdoba, Spain
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Picking WD, Barta ML. The Tip Complex: From Host Cell Sensing to Translocon Formation. Curr Top Microbiol Immunol 2019; 427:173-199. [PMID: 31218507 DOI: 10.1007/82_2019_171] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Type III secretion systems are used by some Gram-negative bacteria to inject effector proteins into targeted eukaryotic cells for the benefit of the bacterium. The type III secretion injectisome is a complex nanomachine comprised of four main substructures including a cytoplasmic sorting platform, an envelope-spanning basal body, an extracellular needle and an exposed needle tip complex. Upon contact with a host cell, secretion is induced, resulting in the formation of a translocon pore in the host membrane. Translocon formation completes the conduit needed for effector secretion into the host cell. Control of type III secretion occurs in response to environmental signals, with the final signal being host cell contact. Secretion control occurs primarily at two sites-the cytoplasmic sorting platform, which determines secretion hierarchy, and the needle tip complex, which is critical for sensing and responding to environmental signals. The best-characterized injectisomes are those from Yersinia, Shigella and Salmonella species where there is a wealth of information on the tip complex and the two translocator proteins. Of these systems, the best characterized from a secretion regulation standpoint is Shigella. In the Shigella system, the tip complex and the first secreted translocon both contribute to secretion control and, thus, both are considered components of the tip complex. In this review, all three of these type III secretion systems are described with discussion focused on the structure and formation of the injectisome tip complex and what is known of the transition from nascent tip complex to assembled translocon pore.
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Affiliation(s)
- William D Picking
- Department of Pharmaceutical Chemistry, University of Kansas, 2030 Becker Drive, Lawrence, 66047, KS, USA.
| | - Michael L Barta
- Higuchi Biosciences, 2099 Constant Ave., Lawrence, 66047, KS, USA.,Catalent Pharma Solutions, 10245 Hickman Mills Drive, Kansas City, 64137, MO, USA
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Salmonella Pathogenicity Island 1 Is Expressed in the Chicken Intestine and Promotes Bacterial Proliferation. Infect Immun 2018; 87:IAI.00503-18. [PMID: 30396895 DOI: 10.1128/iai.00503-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Accepted: 10/24/2018] [Indexed: 12/12/2022] Open
Abstract
Salmonella enterica serovar Enteritidis is a common cause of foodborne illness in the United States. The bacterium can be transmitted to humans via contaminated chicken meat and eggs, and virulence in humans requires type III secretion system 1 (TTSS-1), encoded on Salmonella pathogenicity island 1 (SPI-1). Chickens often carry S Enteritidis subclinically, obscuring the role of SPI-1 in facilitating bacterial colonization. To evaluate the role of SPI-1 in the infection of chicks by Salmonella, we created and utilized strains harboring a stable fluorescent reporter fusion designed to quantify SPI-1 expression within the intestinal tracts of animals. Using mutants unable to express TTSS-1, we demonstrated the important role of the secretion system in facilitating bacterial colonization. We further showed that coinoculation of an SPI-1 mutant with the wild-type strain increased the number of mutant organisms in intestinal tissue and contents, suggesting that the wild type rescues the mutant. Our results support the hypothesis that SPI-1 facilitates S Enteritidis colonization of the chicken and make SPI-1 an attractive target in preventing Salmonella carriage and colonization in chickens to reduce contamination of poultry meat and eggs by this foodborne pathogen.
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Johnson R, Mylona E, Frankel G. TyphoidalSalmonella: Distinctive virulence factors and pathogenesis. Cell Microbiol 2018; 20:e12939. [DOI: 10.1111/cmi.12939] [Citation(s) in RCA: 74] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/06/2018] [Accepted: 07/13/2018] [Indexed: 01/13/2023]
Affiliation(s)
- Rebecca Johnson
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
| | - Elli Mylona
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
| | - Gad Frankel
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences; Imperial College London; London UK
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Salmonella enterica Serovar Typhimurium Increases Functional PD-L1 Synergistically with Gamma Interferon in Intestinal Epithelial Cells via Salmonella Pathogenicity Island 2. Infect Immun 2018; 86:IAI.00674-17. [PMID: 29440366 DOI: 10.1128/iai.00674-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 02/04/2018] [Indexed: 02/04/2023] Open
Abstract
Nontyphoidal serovars of Salmonella enterica are pathogenic bacteria that are common causes of food poisoning. Whereas Salmonella mechanisms of host cell invasion, inflammation, and pathogenesis are mostly well established, a new possible mechanism of immune evasion is being uncovered. Programmed death ligand 1 (PD-L1) is an immunosuppressive membrane protein that binds to activated T cells via their PD-1 receptor and thereby halts their activation. PD-L1 expression plays an essential role in the immunological tolerance of self-antigens but is also exploited for immune evasion by pathogen-infected cells and cancer cells. Here, we show for the first time that Salmonella infection of intestinal epithelial cells causes the induction of PD-L1. The increased expression of PD-L1 through Salmonella infection was seen in both human and rat intestinal epithelial cell lines. We determined that cellular invasion by the bacteria is necessary for PD-L1 induction, potentially indicating that Salmonella strains are delivering mediators from inside the host cell that trigger the increased PD-L1 expression. Using knockout mutants, we determined that this effect largely originates from the Salmonella pathogenicity island 2. We also show for the first time in any cell type that Salmonella combined with gamma interferon (IFN-γ) causes a synergistic induction of PD-L1. Finally, we show that Salmonella plus IFN-γ induction of PD-L1 decreased the cytokine production of activated T cells. Understanding Salmonella immune evasion strategies could generate new therapeutic targets and help to manipulate PD-L1 expression in other diseases.
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HilE Regulates HilD by Blocking DNA Binding in Salmonella enterica Serovar Typhimurium. J Bacteriol 2018; 200:JB.00750-17. [PMID: 29378886 DOI: 10.1128/jb.00750-17] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Accepted: 01/18/2018] [Indexed: 11/20/2022] Open
Abstract
The Salmonella type three secretion system (T3SS), encoded in the Salmonella pathogenicity island 1 (SPI1) locus, mediates the invasion of the host intestinal epithelium. SPI1 expression is dependent upon three AraC-like regulators: HilD, HilC, and RtsA. These regulators act in a complex feed-forward loop to activate each other and hilA, which encodes the activator of the T3SS structural genes. HilD has been shown to be the major integration point of most signals known to activate the expression of the SPI1 T3SS, acting as a switch to control induction of the system. HilE is a negative regulator that acts upon HilD. Here we provide genetic and biochemical data showing that HilE specifically binds to HilD but not to HilC or RtsA. This protein-protein interaction blocks the ability of HilD to bind DNA as shown by both an in vivo reporter system and an in vitro gel shift assay. HilE does not affect HilD dimerization, nor does it control the stability of the HilD protein. We also investigated the role of HilE during the infection of mice using competition assays. Although deletion of hilE does not confer a phenotype, the hilE mutation does suppress the invasion defect conferred by loss of FliZ, which acts as a positive signal controlling HilD protein activity. Together, these data suggest that HilE functions to restrict low-level HilD activity, preventing premature activation of SPI1 until positive inputs reach a threshold required to fully induce the system.IMPORTANCESalmonella is a leading cause of gastrointestinal and systemic disease throughout the world. The SPI1 T3SS is required for Salmonella to induce inflammatory diarrhea and to gain access to underlying tissue. A complex regulatory network controls expression of SPI1 in response to numerous physiological inputs. Most of these signals impinge primarily on HilD translation or activity. The system is triggered when HilD activity crosses a threshold that allows efficient activation of its own promoter. This threshold is set by HilE, which binds to HilD to prevent the inevitable minor fluctuations in HilD activity from inappropriately activating the system. The circuit also serves as a paradigm for systems that must integrate numerous environmental parameters to control regulatory output.
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Paredes-Amaya CC, Valdés-García G, Juárez-González VR, Rudiño-Piñera E, Bustamante VH. The Hcp-like protein HilE inhibits homodimerization and DNA binding of the virulence-associated transcriptional regulator HilD in Salmonella. J Biol Chem 2018. [PMID: 29535187 DOI: 10.1074/jbc.ra117.001421] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
HilD is an AraC-like transcriptional regulator that plays a central role in Salmonella virulence. HilD controls the expression of the genes within the Salmonella pathogenicity island 1 (SPI-1) and of several genes located outside SPI-1, which are mainly required for Salmonella invasion of host cells. The expression, amount, and activity of HilD are tightly controlled by the activities of several factors. The HilE protein represses the expression of the SPI-1 genes through its interaction with HilD; however, the mechanism by which HilE affects HilD is unknown. In this study, we used genetic and biochemical assays revealing how HilE controls the transcriptional activity of HilD. We found that HilD needs to assemble in homodimers to induce expression of its target genes. Our results further indicated that HilE individually interacts with each the central and the C-terminal HilD regions, mediating dimerization and DNA binding, respectively. We also observed that these interactions consistently inhibit HilD dimerization and DNA binding. Interestingly, a computational analysis revealed that HilE shares sequence and structural similarities with Hcp proteins, which act as structural components of type 6 secretion systems in Gram-negative bacteria. In conclusion, our results uncover the molecular mechanism by which the Hcp-like protein HilE controls dimerization and DNA binding of the virulence-promoting transcriptional regulator HilD. Our findings may indicate that HilE's activity represents a functional adaptation during the evolution of Salmonella pathogenicity.
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Affiliation(s)
| | - Gilberto Valdés-García
- Molecular Medicine and Bioprocesses, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Víctor R Juárez-González
- Molecular Medicine and Bioprocesses, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Enrique Rudiño-Piñera
- Molecular Medicine and Bioprocesses, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
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Comparison of Salmonella enterica Serovars Typhi and Typhimurium Reveals Typhoidal Serovar-Specific Responses to Bile. Infect Immun 2018; 86:IAI.00490-17. [PMID: 29229736 PMCID: PMC5820949 DOI: 10.1128/iai.00490-17] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 12/06/2017] [Indexed: 01/19/2023] Open
Abstract
Salmonella enterica serovars Typhi and Typhimurium cause typhoid fever and gastroenteritis, respectively. A unique feature of typhoid infection is asymptomatic carriage within the gallbladder, which is linked with S. Typhi transmission. Despite this, S. Typhi responses to bile have been poorly studied. Transcriptome sequencing (RNA-Seq) of S. Typhi Ty2 and a clinical S. Typhi isolate belonging to the globally dominant H58 lineage (strain 129-0238), as well as S. Typhimurium 14028, revealed that 249, 389, and 453 genes, respectively, were differentially expressed in the presence of 3% bile compared to control cultures lacking bile. fad genes, the actP-acs operon, and putative sialic acid uptake and metabolism genes (t1787 to t1790) were upregulated in all strains following bile exposure, which may represent adaptation to the small intestine environment. Genes within the Salmonella pathogenicity island 1 (SPI-1), those encoding a type IIII secretion system (T3SS), and motility genes were significantly upregulated in both S. Typhi strains in bile but downregulated in S. Typhimurium. Western blots of the SPI-1 proteins SipC, SipD, SopB, and SopE validated the gene expression data. Consistent with this, bile significantly increased S. Typhi HeLa cell invasion, while S. Typhimurium invasion was significantly repressed. Protein stability assays demonstrated that in S. Typhi the half-life of HilD, the dominant regulator of SPI-1, is three times longer in the presence of bile; this increase in stability was independent of the acetyltransferase Pat. Overall, we found that S. Typhi exhibits a specific response to bile, especially with regard to virulence gene expression, which could impact pathogenesis and transmission.
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Urdaneta V, Casadesús J. Adaptation of Salmonella enterica to bile: essential role of AcrAB-mediated efflux. Environ Microbiol 2018; 20:1405-1418. [PMID: 29349886 DOI: 10.1111/1462-2920.14047] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2017] [Revised: 01/11/2018] [Accepted: 01/14/2018] [Indexed: 12/25/2022]
Abstract
Adaptation to bile is the ability to endure the lethal effects of bile salts after growth on sublethal concentrations. Surveys of adaptation to bile in Salmonella enterica ser. Tyhimurium reveal that active efflux is essential for adaptation while other bacterial functions involved in bile resistance are not. Among S. enterica mutants lacking one or more efflux systems, only strains lacking AcrAB are unable to adapt, thus revealing an essential role for AcrAB. Transcription of the acrAB operon is upregulated in the presence of a sublethal concentration of sodium deoxycholate (DOC) while other efflux loci are either weakly upregulated or irresponsive. Upregulation of acrAB transcription is strong during exponential growth, and weak in stationary cultures. Single cell analysis of ethidium bromide accumulation indicates that DOC-induced AcrAB-mediated efflux occurs in both exponential and stationary cultures. Upregulation of acrAB expression may thus be crucial at early stages of adaptation, while sustained AcrAB activity may be sufficient to confer bile resistance in nondividing cells.
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Affiliation(s)
- Verónica Urdaneta
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, Sevilla, Spain
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Apartado 1095, Sevilla, Spain
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Anderson CJ, Kendall MM. Salmonella enterica Serovar Typhimurium Strategies for Host Adaptation. Front Microbiol 2017; 8:1983. [PMID: 29075247 PMCID: PMC5643478 DOI: 10.3389/fmicb.2017.01983] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 09/26/2017] [Indexed: 12/21/2022] Open
Abstract
Bacterial pathogens must sense and respond to newly encountered host environments to regulate the expression of critical virulence factors that allow for niche adaptation and successful colonization. Among bacterial pathogens, non-typhoidal serovars of Salmonella enterica, such as serovar Typhimurium (S. Tm), are a primary cause of foodborne illnesses that lead to hospitalizations and deaths worldwide. S. Tm causes acute inflammatory diarrhea that can progress to invasive systemic disease in susceptible patients. The gastrointestinal tract and intramacrophage environments are two critically important niches during S. Tm infection, and each presents unique challenges to limit S. Tm growth. The intestinal tract is home to billions of commensal microbes, termed the microbiota, which limits the amount of available nutrients for invading pathogens such as S. Tm. Therefore, S. Tm encodes strategies to manipulate the commensal population and side-step this nutritional competition. During subsequent stages of disease, S. Tm resists host immune cell mechanisms of killing. Host cells use antimicrobial peptides, acidification of vacuoles, and nutrient limitation to kill phagocytosed microbes, and yet S. Tm is able to subvert these defense systems. In this review, we discuss recently described molecular mechanisms that S. Tm uses to outcompete the resident microbiota within the gastrointestinal tract. S. Tm directly eliminates close competitors via bacterial cell-to-cell contact as well as by stimulating a host immune response to eliminate specific members of the microbiota. Additionally, S. Tm tightly regulates the expression of key virulence factors that enable S. Tm to withstand host immune defenses within macrophages. Additionally, we highlight the chemical and physical signals that S. Tm senses as cues to adapt to each of these environments. These strategies ultimately allow S. Tm to successfully adapt to these two disparate host environments. It is critical to better understand bacterial adaptation strategies because disruption of these pathways and mechanisms, especially those shared by multiple pathogens, may provide novel therapeutic intervention strategies.
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Affiliation(s)
- Christopher J Anderson
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine,, Charlottesville, VA, United States
| | - Melissa M Kendall
- Department of Microbiology, Immunology, and Cancer Biology, University of Virginia School of Medicine,, Charlottesville, VA, United States
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Urdaneta V, Casadesús J. Interactions between Bacteria and Bile Salts in the Gastrointestinal and Hepatobiliary Tracts. Front Med (Lausanne) 2017; 4:163. [PMID: 29043249 PMCID: PMC5632352 DOI: 10.3389/fmed.2017.00163] [Citation(s) in RCA: 228] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 09/19/2017] [Indexed: 12/25/2022] Open
Abstract
Bile salts and bacteria have intricate relationships. The composition of the intestinal pool of bile salts is shaped by bacterial metabolism. In turn, bile salts play a role in intestinal homeostasis by controlling the size and the composition of the intestinal microbiota. As a consequence, alteration of the microbiome-bile salt homeostasis can play a role in hepatic and gastrointestinal pathological conditions. Intestinal bacteria use bile salts as environmental signals and in certain cases as nutrients and electron acceptors. However, bile salts are antibacterial compounds that disrupt bacterial membranes, denature proteins, chelate iron and calcium, cause oxidative damage to DNA, and control the expression of eukaryotic genes involved in host defense and immunity. Bacterial species adapted to the mammalian gut are able to endure the antibacterial activities of bile salts by multiple physiological adjustments that include remodeling of the cell envelope and activation of efflux systems and stress responses. Resistance to bile salts permits that certain bile-resistant pathogens can colonize the hepatobiliary tract, and an outstanding example is the chronic infection of the gall bladder by Salmonella enterica. A better understanding of the interactions between bacteria and bile salts may inspire novel therapeutic strategies for gastrointestinal and hepatobiliary diseases that involve microbiome alteration, as well as novel schemes against bacterial infections.
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Affiliation(s)
- Verónica Urdaneta
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
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Signal transduction pathway mediated by the novel regulator LoiA for low oxygen tension induced Salmonella Typhimurium invasion. PLoS Pathog 2017; 13:e1006429. [PMID: 28575106 PMCID: PMC5476282 DOI: 10.1371/journal.ppat.1006429] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 06/19/2017] [Accepted: 05/23/2017] [Indexed: 02/03/2023] Open
Abstract
Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major intestinal pathogen of both humans and animals. Salmonella pathogenicity island 1 (SPI-1)-encoded virulence genes are required for S. Typhimurium invasion. While oxygen (O2) limitation is an important signal for SPI-1 induction under host conditions, how the signal is received and integrated to the central SPI-1 regulatory system in S. Typhimurium is not clear. Here, we report a signal transduction pathway that activates SPI-1 expression in response to low O2. A novel regulator encoded within SPI-14 (STM14_1008), named LoiA (low oxygen induced factor A), directly binds to the promoter and activates transcription of hilD, leading to the activation of hilA (the master activator of SPI-1). Deletion of loiA significantly decreased the transcription of hilA, hilD and other representative SPI-1 genes (sipB, spaO, invH, prgH and invF) under low O2 conditions. The response of LoiA to the low O2 signal is mediated by the ArcB/ArcA two-component system. Deletion of either arcA or arcB significantly decreased transcription of loiA under low O2 conditions. We also confirmed that SPI-14 contributes to S. Typhimurium virulence by affecting invasion, and that loiA is the virulence determinant of SPI-14. Mice infection assays showed that S. Typhimurium virulence was severely attenuated by deletion of either the entire SPI-14 region or the single loiA gene after oral infection, while the virulence was not affected by either deletion after intraperitoneal infection. The signal transduction pathway described represents an important mechanism for S. Typhimurium to sense and respond to low O2 conditions of the host intestinal tract for invasion. SPI-14-encoded loiA is an essential element of this pathway that integrates the low O2 signal into the SPI-1 regulatory system. Acquisition of SPI-14 is therefore crucial for the evolution of S. Typhimurium as an intestinal pathogen. Salmonella enterica serovar Typhimurium (S. Typhimurium) is a major intestinal pathogen of both humans and animals. Salmonella pathogenicity island 1 (SPI-1) is required for host cell invasion by S. Typhimurium. Expression of SPI-1 genes is induced by low oxygen (O2) tension under host conditions, but the relevant regulatory mechanisms are not clear. Here, we report a low O2-induced signal transduction pathway for the activation of SPI-1 expression in S. Typhimurium. A novel regulator, STM14_1008 (named LoiA), encoded within SPI-14 directly activates hilD, which in turn activates hilA (the master activator of SPI-1), and thus other SPI-1 genes under O2-limited conditions. The response of LoiA to the low O2 signal is mediated by the ArcB/ArcA two-component system. We also confirmed that SPI-14 contributes to S. Typhimurium virulence by affecting invasion, with loiA as the virulence determinant. This novel SPI-1 activation pathway can be used by S. Typhimurium to sense and respond to low O2 conditions of the host intestinal tract for invasion. Acquisition of SPI-14 is therefore very important for the evolution of S. Typhimurium virulence by providing an essential component of this pathway, loiA.
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Rivera-Cancel G, Orth K. Biochemical basis for activation of virulence genes by bile salts in Vibrio parahaemolyticus. Gut Microbes 2017; 8:366-373. [PMID: 28129014 PMCID: PMC5570421 DOI: 10.1080/19490976.2017.1287655] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Bile salts act as a stressor to bacteria that transit the intestinal tract. Enteric pathogens have hijacked bile as an intestinal signal to regulate virulence factors. We recently demonstrated that Vibrio parahemolyticus senses bile salts via a heterodimeric receptor formed by the periplasmic domains of inner-membrane proteins VtrA and VtrC. Crystal structures of the periplasmic complex reveal that VtrA and VtrC form a β-barrel that binds bile salts in its hydrophobic interior to activate the VtrA cytoplasmic DNA-binding domain. Proteins with the same domain arrangement as VtrA and VtrC are widespread in Vibrio and related bacteria, where they are involved in regulating virulence and other unknown functions. Here we discuss our findings and review current knowledge on VtrA and VtrC homologs. We propose that signaling by these membrane-bound transcription factors can be advantageous for the regulation of membrane and secretory proteins.
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Affiliation(s)
- Giomar Rivera-Cancel
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Kim Orth
- Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas, USA,Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas, USA,CONTACT Kim Orth
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Martínez-Flores I, Pérez-Morales D, Sánchez-Pérez M, Paredes CC, Collado-Vides J, Salgado H, Bustamante VH. In silico clustering of Salmonella global gene expression data reveals novel genes co-regulated with the SPI-1 virulence genes through HilD. Sci Rep 2016; 6:37858. [PMID: 27886269 PMCID: PMC5122947 DOI: 10.1038/srep37858] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2016] [Accepted: 11/02/2016] [Indexed: 01/04/2023] Open
Abstract
A wide variety of Salmonella enterica serovars cause intestinal and systemic infections to humans and animals. Salmonella Patogenicity Island 1 (SPI-1) is a chromosomal region containing 39 genes that have crucial virulence roles. The AraC-like transcriptional regulator HilD, encoded in SPI-1, positively controls the expression of the SPI-1 genes, as well as of several other virulence genes located outside SPI-1. In this study, we applied a clustering method to the global gene expression data of S. enterica serovar Typhimurium from the COLOMBOS database; thus genes that show an expression pattern similar to that of SPI-1 genes were selected. This analysis revealed nine novel genes that are co-expressed with SPI-1, which are located in different chromosomal regions. Expression analyses and protein-DNA interaction assays showed regulation by HilD for six of these genes: gtgE, phoH, sinR, SL1263 (lpxR) and SL4247 were regulated directly, whereas SL1896 was regulated indirectly. Interestingly, phoH is an ancestral gene conserved in most of bacteria, whereas the other genes show characteristics of genes acquired by Salmonella. A role in virulence has been previously demonstrated for gtgE, lpxR and sinR. Our results further expand the regulon of HilD and thus identify novel possible Salmonella virulence genes.
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Affiliation(s)
- Irma Martínez-Flores
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Deyanira Pérez-Morales
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Mishael Sánchez-Pérez
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Claudia C Paredes
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Julio Collado-Vides
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Heladia Salgado
- Programa de Genómica Computacional, Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
| | - Víctor H Bustamante
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62210, México
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