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Feng J, Zheng Y, Ma W, Weng D, Peng D, Xu Y, Wang Z, Wang X. A synthetic antibiotic class with a deeply-optimized design for overcoming bacterial resistance. Nat Commun 2024; 15:6040. [PMID: 39019927 PMCID: PMC11255307 DOI: 10.1038/s41467-024-50453-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Accepted: 07/10/2024] [Indexed: 07/19/2024] Open
Abstract
The lack of new drugs that are effective against antibiotic-resistant bacteria has caused increasing concern in global public health. Based on this study, we report development of a modified antimicrobial drug through structure-based drug design (SBDD) and modular synthesis. The optimal modified compound, F8, was identified, which demonstrated in vitro and in vivo broad-spectrum antibacterial activity against drug-resistant bacteria and effectively mitigated the development of resistance. F8 exhibits significant bactericidal activity against bacteria resistant to antibiotics such as methicillin, polymyxin B, florfenicol (FLO), doxycycline, ampicillin and sulfamethoxazole. In a mouse model of drug-resistant bacteremia, F8 was found to increase survival and significantly reduce bacterial load in infected mice. Multi-omics analysis (transcriptomics, proteomics, and metabolomics) have indicated that ornithine carbamoyl transferase (arcB) is a antimicrobial target of F8. Further molecular docking, Isothermal Titration Calorimetry (ITC), and Differential Scanning Fluorimetry (DSF) studies verified arcB as a effective target for F8. Finally, mechanistic studies suggest that F8 competitively binds to arcB, disrupting the bacterial cell membrane and inducing a certain degree of oxidative damage. Here, we report F8 as a promising candidate drug for the development of antibiotic formulations to combat antibiotic-resistant bacteria-associated infections.
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Affiliation(s)
- Jin Feng
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Youle Zheng
- MAO Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Wanqing Ma
- MAO Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Defeng Weng
- MAO Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Dapeng Peng
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, China
- MAO Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, China
| | - Yindi Xu
- Institute of Animal Husbandry and Veterinary Research, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China
| | - Zhifang Wang
- Institute of Animal Husbandry and Veterinary Research, Henan Academy of Agricultural Sciences, Zhengzhou, Henan, China
| | - Xu Wang
- National Reference Laboratory of Veterinary Drug Residues (HZAU) and MAO Key Laboratory for Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, China.
- MAO Laboratory for Risk Assessment of Quality and Safety of Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, China.
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Wu J, McAuliffe O, O'Byrne CP. Trehalose transport occurs via TreB in Listeria monocytogenes and it influences biofilm development and acid resistance. Int J Food Microbiol 2023; 394:110165. [PMID: 36933360 DOI: 10.1016/j.ijfoodmicro.2023.110165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2022] [Revised: 02/09/2023] [Accepted: 02/28/2023] [Indexed: 03/12/2023]
Abstract
Listeria monocytogenes is a pathogenic bacterium that can inhabit a diverse range of environmental niches. This is largely attributed to the high proportion of carbohydrate-specific phosphotransferase system (PTS) genes in its genome. Carbohydrates can be assimilated as sources of energy but additionally they can serve as niche-specific cues for L. monocytogenes to shape its global gene expression, in order to cope with anticipated stresses. To examine carbon source utilization among wild L. monocytogenes isolates and to understand underlying molecular mechanisms, a diverse collection of L. monocytogenes strains (n = 168) with whole genome sequence (WGS) data available was screened for the ability to grow in chemically defined media with different carbon sources. The majority of the strains grew in glucose, mannose, fructose, cellobiose, glycerol, trehalose, and sucrose. Maltose, lactose, and rhamnose supported slower growth while ribose did not support any growth. In contrast to other strains, strain1386, which belonged to clonal complex 5 (CC5), was unable to grow on trehalose as a sole carbon source. WGS data revealed that it carried a substitution (N352K) in a putative PTS EIIBC trehalose transporter, TreB, while this asparagine residue is conserved in other strains in this collection. Spontaneous mutants of strain 1386 that could grow in trehalose were found to harbour a reversion of the substitution in TreB. These results provide genetic evidence that TreB is responsible for trehalose uptake and that the N352 residue is essential for TreB activity. Moreover, reversion mutants also restored other unusual phenotypes that strain 1386 displayed, i.e. altered colony morphology, impaired biofilm development, and reduced acid resistance. Transcriptional analysis at stationary phase with buffered BHI media revealed that trehalose metabolism positively influences the transcription of genes encoding amino acid-based acid resistance mechanisms. In summary, our results demonstrated that N352 is key to the function of the sole trehalose transporter TreB in L. monocytogenes and suggest that trehalose metabolism alters physiology to favour biofilm development and acid stress resistance. Moreover, since strain 1386 is among the strains recommended by the European Union Reference Laboratory for conducting food challenge studies in order to determine whether or not L. monocytogenes can grow in food, these findings have important implications for food safety.
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Affiliation(s)
- Jialun Wu
- Bacterial Stress Response Group, Microbiology, School of Biological & Chemical Sciences, University of Galway, Galway H91 TK33, Ireland
| | | | - Conor P O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Biological & Chemical Sciences, University of Galway, Galway H91 TK33, Ireland.
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Li P, Zong W, Zhang Z, Lv W, Ji X, Zhu D, Du X, Wang S. Effects and molecular mechanism of flagellar gene flgK on the motility, adhesion/invasion, and desiccation resistance of Cronobacter sakazakii. Food Res Int 2023; 164:112418. [PMID: 36738023 DOI: 10.1016/j.foodres.2022.112418] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 12/21/2022] [Accepted: 12/26/2022] [Indexed: 12/29/2022]
Abstract
Cronobacter sakazakii (C. sakazakii), a food-borne pathogen, can infect neonates, elderly and immunocompromised populations with a high infection and mortality rate. However, the specific molecular mechanism of its motility, biofilm formation, cell adhesion, and desiccation resistance remains unclear, and flagellum hook associated protein (FlgK), a main component of the flagellar complex, may be an important determinant of its virulence and desiccation resistance. In this study, the flgK mutant strain (ΔflgK) was constructed using the homologous recombination method, and the cpflgK complementary strain was obtained by gene complementation, followed by analysis of the difference between the wild type (WT), mutant, and complementary strains in mobility, biofilm formation, cell adhesion, and desiccation resistance. Results indicated that flgK gene played a positive role in motility and invasion, with no significant effect on biofilm formation. Interestingly, flagellar assembly gene deletion showed increased resistance of C. sakazakii to dehydration. The mechanism underlying the negative correlation of flgK gene with dehydration resistance was further investigated by using the high-throughput sequencing technology to compare the gene expression between WT and ΔflgK strains after drying. The results revealed up-regulation in the expression of 54 genes, including genes involved in osmosis and formate dehydrogenase, while down-regulation in the expression of 50 genes, including genes involved in flagellum hook and nitrate reductase. qRT-PCR analysis of the RNA-seq data further indicated that the flgK gene played an important role in the environmental stress resistance of C. sakazakii by up-regulating the formate dehydrogenase, betaine synthesis, and arginine deiminase pathways, due to dynamic proton imbalance caused by lack of flagella. This study facilitates our understanding of the roles of flgK in motion-related functions and the molecular mechanism of desiccation resistance in C. sakazakii.
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Affiliation(s)
- Ping Li
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China
| | - Wenyue Zong
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China
| | - Zhengyang Zhang
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China
| | - Wen Lv
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China
| | - Xuemeng Ji
- Tianjin Key Laboratory of Food Science and Health, College of Medicine, Nankai University, Tianjin 300071, China
| | - Dongdong Zhu
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China
| | - Xinjun Du
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China.
| | - Shuo Wang
- State Key Laboratory of Food Nutrition and Safety, College of Food Science and Engineering, Tianjin University of Science and Technology, Tianjin 300457, China; Tianjin Key Laboratory of Food Science and Health, College of Medicine, Nankai University, Tianjin 300071, China.
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Wu JF, Wei XP, Li JY, Sun WX. Recombinant Expression and Characterization of an Arginine Deiminase from Pseudomonas sp. LJY. APPL BIOCHEM MICRO+ 2022. [DOI: 10.1134/s0003683822060163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Guerreiro DN, Boyd A, O'Byrne CP. The stressosome is required to transduce low pH signals leading to increased transcription of the amino acid-based acid tolerance mechanisms in Listeria monocytogenes. Access Microbiol 2022; 4:acmi000455. [PMID: 36415544 PMCID: PMC9675040 DOI: 10.1099/acmi.0.000455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 08/02/2022] [Indexed: 10/03/2023] Open
Abstract
Increasing proton concentration in the environment represents a potentially lethal stress for single-celled microorganisms. To survive in an acidifying environment, the foodborne pathogen Listeria monocytogenes quickly activates the alternative sigma factor B (σB), resulting in upregulation of the general stress response (GSR) regulon. Activation of σB is regulated by the stressosome, a multi-protein sensory complex involved in stress detection and signal transduction. In this study, we used L. monocytogenes strains harbouring two stressosome mutants to investigate the role of this complex in triggering expression of known amino acid-based resistance mechanisms in response to low pH. We found that expression of glutamate decarboxylase (gadD3) and arginine and agmatine deiminases (arcA and aguA1, respectively) were upregulated upon acid shock (pH 5 for 15 min) in a stressosome-dependent manner. In contrast, transcription of the arg operons (argGH and argCJBDF), which encode enzymes for the l-arginine biosynthesis pathway, were upregulated upon acid shock in a stressosome-independent manner. Finally, we found that transcription of argR, which encodes a transcriptional regulator of the arc and arg operons, was largely unaffected by acidic shock. Thus, our findings suggest that the stressosome plays a role in activating amino acid-based pH homeostatic mechanisms in L. monocytogenes . Additionally, we show that genes encoding the l-arginine biosynthesis pathway are highly upregulated under acidic conditions, suggesting that intracellular arginine can help withstand environmental acidification in this pathogen.
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Affiliation(s)
- Duarte N. Guerreiro
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
| | - Aoife Boyd
- Pathogenic Mechanisms Research Group, Microbiology, School of Natural Sciences, National University of Ireland, Galway, Ireland
| | - Conor P. O'Byrne
- Bacterial Stress Response Group, Microbiology, School of Biological and Chemical Sciences, National University of Ireland, Galway, Ireland
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The ArcAB Two-Component System: Function in Metabolism, Redox Control, and Infection. Microbiol Mol Biol Rev 2022; 86:e0011021. [PMID: 35442087 PMCID: PMC9199408 DOI: 10.1128/mmbr.00110-21] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
ArcAB, also known as the Arc system, is a member of the two-component system family of bacterial transcriptional regulators and is composed of sensor kinase ArcB and response regulator ArcA. In this review, we describe the structure and function of these proteins and assess the state of the literature regarding ArcAB as a sensor of oxygen consumption. The bacterial quinone pool is the primary modulator of ArcAB activity, but questions remain for how this regulation occurs. This review highlights the role of quinones and their oxidation state in activating and deactivating ArcB and compares competing models of the regulatory mechanism. The cellular processes linked to ArcAB regulation of central metabolic pathways and potential interactions of the Arc system with other regulatory systems are also reviewed. Recent evidence for the function of ArcAB under aerobic conditions is challenging the long-standing characterization of this system as strictly an anaerobic global regulator, and the support for additional ArcAB functionality in this context is explored. Lastly, ArcAB-controlled cellular processes with relevance to infection are assessed.
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Chen Q, Yang X, Meng Q, Zhao L, Yuan Y, Chi W, He L, Shi K, Liu S. Integrative multiomics analysis of the acid stress response of Oenococcus oeni mutants at different growth stages. Food Microbiol 2021; 102:103905. [PMID: 34809937 DOI: 10.1016/j.fm.2021.103905] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 09/13/2021] [Accepted: 09/15/2021] [Indexed: 02/07/2023]
Abstract
BACKGROUND Acid stress is one of the most important environmental stresses that adversely affect the growth of lactic acid bacteria (LAB), such as Oenococcus oeni which was isolated from grape-berries and mainly used in wine fermentation. The aim of this paper is to comprehensively characterize the mechanisms of acid stress regulation in O. oeni and to provide a viable theoretical basis for breed and improvement of existing LAB. METHOD First, six O. oeni mutants with acid-sensitive (strains b2, a1, c2) and acid-tolerant (strains b1, a3, c1) phenotypes were screened from three wild-type O. oeni, and then their genome (sequencing), transcriptome and metabolome (LC-MS/MS) were examined. RESULTS A total of 459 genes were identified with one or more intragenic single nucleotide polymorphisms (SNPs) in these mutants, and were extensively involved in metabolism and cellular functions with a high mutation rates in purine (46%) and pyrimidine (48%) metabolic pathways. There were 210 mutated genes that cause significant changes in expression levels. In addition, 446 differentially accumulated metabolites were detected, and they were consistently detected at relatively high levels in the acid-tolerant O. oeni mutant. The levels of intracellular differentially expressed genes and differential metabolites changed with increasing culture time. CONCLUSION The integrative pathways analysis showed that the intracellular response associated with acid regulation differed significantly between acid-sensitive and acid-tolerant O. oeni mutants, and also changed at different growth stages.
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Affiliation(s)
- Qiling Chen
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China; College of Food Science and Pharmacy, Xinjiang Agricultural University, Urumqi, Xinjiang, China
| | - Xiangke Yang
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China; Henan University of Animal Husbandry and Economy, Zhenzhou, Henan, China
| | - Qiang Meng
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China
| | - Lili Zhao
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China
| | - Yuxin Yuan
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China
| | - Wei Chi
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China
| | - Ling He
- College of Horticulture, Northwest A&F University, Yangling, Shaanxi, China
| | - Kan Shi
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China; Ningxia Helan Mountain's East Foothill Wine Experiment and Demonstration Station of, Northwest A&F University, Yongning, Ningxia, 750104, China.
| | - Shuwen Liu
- College of Enology, Northwest A&F University, Yangling, Shaanxi, China; Ningxia Helan Mountain's East Foothill Wine Experiment and Demonstration Station of, Northwest A&F University, Yongning, Ningxia, 750104, China.
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Arcari T, Feger ML, Guerreiro DN, Wu J, O’Byrne CP. Comparative Review of the Responses of Listeria monocytogenes and Escherichia coli to Low pH Stress. Genes (Basel) 2020; 11:genes11111330. [PMID: 33187233 PMCID: PMC7698193 DOI: 10.3390/genes11111330] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 11/03/2020] [Accepted: 11/09/2020] [Indexed: 02/07/2023] Open
Abstract
Acidity is one of the principal physicochemical factors that influence the behavior of microorganisms in any environment, and their response to it often determines their ability to grow and survive. Preventing the growth and survival of pathogenic bacteria or, conversely, promoting the growth of bacteria that are useful (in biotechnology and food production, for example), might be improved considerably by a deeper understanding of the protective responses that these microorganisms deploy in the face of acid stress. In this review, we survey the molecular mechanisms used by two unrelated bacterial species in their response to low pH stress. We chose to focus on two well-studied bacteria, Escherichia coli (phylum Proteobacteria) and Listeria monocytogenes (phylum Firmicutes), that have both evolved to be able to survive in the mammalian gastrointestinal tract. We review the mechanisms that these species use to maintain a functional intracellular pH as well as the protective mechanisms that they deploy to prevent acid damage to macromolecules in the cells. We discuss the mechanisms used to sense acid in the environment and the regulatory processes that are activated when acid is encountered. We also highlight the specific challenges presented by organic acids. Common themes emerge from this comparison as well as unique strategies that each species uses to cope with acid stress. We highlight some of the important research questions that still need to be addressed in this fascinating field.
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Kang S, Meng Y, Cheng X, Tu J, Guo D, Xu Y, Liang S, Xia X, Shi C. Effects of 405-nm LED Treatment on the Resistance of Listeria monocytogenes to Subsequent Environmental Stresses. Front Microbiol 2019; 10:1907. [PMID: 31474971 PMCID: PMC6706791 DOI: 10.3389/fmicb.2019.01907] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Accepted: 08/05/2019] [Indexed: 11/13/2022] Open
Abstract
Listeria monocytogenes can persist under a wide range of stress conditions, contributing to its ubiquitous distribution and unique pathogenic traits. Light from light-emitting diodes (LEDs) has recently been shown to inactivate various pathogens. Thus, the aim of the present study was to evaluate the effects of light treatment using a 405-nm LED on the subsequent resistance of L. monocytogenes to environmental stresses, including oxidative stress, ultraviolet (UV) irradiation, low temperature, osmotic pressure, simulated gastric fluid (SGF), and bile salts. Following 405-nm LED illumination at 4°C for 150 min, the survival of L. monocytogenes was examined after exposure to oxidative stress (0.04% H2O2), UV irradiation (253.7 nm), low temperature (4°C), osmotic pressure (10, 15, or 20% NaCl), SGF (pH 2.5), or bile salts (2%). The mechanisms responsible for changes in stress tolerance were identified by assessing the transcriptional responses and membrane integrity of L. monocytogenes. The 405-nm LED treatment reduced the resistance of L. monocytogenes to all the stresses tested. Reverse transcription quantitative real-time polymerase chain reaction analysis indicated that the transcription of multiple genes associated with stress resistance, including betL, gbuA, oppA, fri, bsh, and arcA, was reduced by 405-nm LED. Confocal laser scanning microscopy revealed that 405-nm LED treatment disrupted the integrity of the L. monocytogenes cell membrane compared with untreated bacteria. Therefore, 405-nm LED illumination appears to reduce the resistance of L. monocytogenes to various stress conditions. These findings suggest that 405-nm LED treatment could be used to effectively prevent and/or control with L. monocytogenes contamination along the entire food-processing chain, from production to consumption.
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Affiliation(s)
- Shenmin Kang
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Yujie Meng
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Xiaomeng Cheng
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Junhong Tu
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Du Guo
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Yunfeng Xu
- College of Food and Bioengineering, Henan University of Science and Technology, Luoyang, China
| | - Sen Liang
- Beijing Advanced Innovation Center for Food Nutrition and Human Health, Beijing Technology and Business University, Beijing, China
| | - Xiaodong Xia
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
| | - Chao Shi
- College of Food Science and Engineering, Northwest A&F University, Yangling, China
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iTRAQ-based quantitative proteomic analysis reveals potential virulence factors of Erysipelothrix rhusiopathiae. J Proteomics 2017; 160:28-37. [DOI: 10.1016/j.jprot.2017.03.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 03/01/2017] [Accepted: 03/04/2017] [Indexed: 12/28/2022]
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Cheng C, Dong Z, Han X, Sun J, Wang H, Jiang L, Yang Y, Ma T, Chen Z, Yu J, Fang W, Song H. Listeria monocytogenes 10403S Arginine Repressor ArgR Finely Tunes Arginine Metabolism Regulation under Acidic Conditions. Front Microbiol 2017; 8:145. [PMID: 28217122 PMCID: PMC5291005 DOI: 10.3389/fmicb.2017.00145] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Accepted: 01/19/2017] [Indexed: 11/13/2022] Open
Abstract
Listeria monocytogenes is able to colonize human and animal intestinal tracts and to subsequently cross the intestinal barrier, causing systemic infection. For successful establishment of infection, L. monocytogenes must survive the low pH environment of the stomach. L. monocytogenes encodes a functional ArgR, a transcriptional regulator belonging to the ArgR/AhrC arginine repressor family. We aimed at clarifying the specific functions of ArgR in arginine metabolism regulation, and more importantly, in acid tolerance of L. monocytogenes. We showed that ArgR in the presence of 10 mM arginine represses transcription and expression of the argGH and argCJBDF operons, indicating that L. monocytogenes ArgR plays the classical role of ArgR/AhrC family proteins in feedback inhibition of the arginine biosynthetic pathway. Notably, transcription and expression of arcA (encoding arginine deiminase) and sigB (encoding an alternative sigma factor B) were also markedly repressed by ArgR when bacteria were exposed to pH 5.5 in the absence of arginine. However, addition of arginine enabled ArgR to derepress the transcription and expression of these two genes. Electrophoretic mobility shift assays showed that ArgR binds to the putative ARG boxes in the promoter regions of argC, argG, arcA, and sigB. Reporter gene analysis with gfp under control of the argG promoter demonstrated that ArgR was able to activate the argG promoter. Unexpectedly, deletion of argR significantly increased bacterial survival in BHI medium adjusted to pH 3.5 with lactic acid. We conclude that this phenomenon is due to activation of arcA and sigB. Collectively, our results show that L. monocytogenes ArgR finely tunes arginine metabolism through negative transcriptional regulation of the arginine biosynthetic operons and of the catabolic arcA gene in an arginine-independent manner during lactic acid-induced acid stress. ArgR also appears to activate catabolism as well as sigB transcription by anti-repression in an arginine-dependent way.
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Affiliation(s)
- Changyong Cheng
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Zhimei Dong
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Xiao Han
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Jing Sun
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Hang Wang
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Li Jiang
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Yongchun Yang
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Tiantian Ma
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Zhongwei Chen
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Jing Yu
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
| | - Weihuan Fang
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F UniversityLin'an, China; Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Institute of Preventive Veterinary Medicine, Zhejiang UniversityHangzhou, China
| | - Houhui Song
- College of Animal Science and Technology, China-Australia Joint-Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, Zhejiang A&F University Lin'an, China
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12
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NicAogáin K, O’Byrne CP. The Role of Stress and Stress Adaptations in Determining the Fate of the Bacterial Pathogen Listeria monocytogenes in the Food Chain. Front Microbiol 2016; 7:1865. [PMID: 27933042 PMCID: PMC5120093 DOI: 10.3389/fmicb.2016.01865] [Citation(s) in RCA: 117] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Accepted: 11/04/2016] [Indexed: 12/15/2022] Open
Abstract
The foodborne pathogen Listeria monocytogenes is a highly adaptable organism that can persist in a wide range of environmental and food-related niches. The consumption of contaminated ready-to-eat foods can cause infections, termed listeriosis, in vulnerable humans, particularly those with weakened immune systems. Although these infections are comparatively rare they are associated with high mortality rates and therefore this pathogen has a significant impact on food safety. L. monocytogenes can adapt to and survive a wide range of stress conditions including low pH, low water activity, and low temperature, which makes it problematic for food producers who rely on these stresses for preservation. Stress tolerance in L. monocytogenes can be explained partially by the presence of the general stress response (GSR), a transcriptional response under the control of the alternative sigma factor sigma B (σB) that reconfigures gene transcription to provide homeostatic and protective functions to cope with the stress. Within the host σB also plays a key role in surviving the harsh conditions found in the gastrointestinal tract. As the infection progresses beyond the GI tract L. monocytogenes uses an intracellular infectious cycle to propagate, spread and remain protected from the host's humoral immunity. Many of the virulence genes that facilitate this infectious cycle are under the control of a master transcriptional regulator called PrfA. In this review we consider the environmental reservoirs that enable L. monocytogenes to gain access to the food chain and discuss the stresses that the pathogen must overcome to survive and grow in these environments. The overlap that exists between stress tolerance and virulence is described. We review the principal measures that are used to control the pathogen and point to exciting new approaches that might provide improved means of control in the future.
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Affiliation(s)
| | - Conor P. O’Byrne
- Bacterial Stress Response Group, Microbiology, School of Natural Sciences, College of Science, National University of IrelandGalway, Ireland
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13
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Cheng C, Wang X, Dong Z, Shao C, Yang Y, Fang W, Fang C, Wang H, Yang M, Jiang L, Zhou X, Song H. Aminopeptidase T of M29 Family Acts as A Novel Intracellular Virulence Factor for Listeria monocytogenes Infection. Sci Rep 2015; 5:17370. [PMID: 26610705 PMCID: PMC4661694 DOI: 10.1038/srep17370] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 10/29/2015] [Indexed: 01/18/2023] Open
Abstract
The foodborne pathogen Listeria monocytogenes employs a number of virulence determinants including metalloproteases to infect hosts. Here for the first time, we identified an M29 family aminopeptidase T (encoded by lmo1603) from L. monocytogenes that possesses a typical feature to catalyze the cleavage of amino acids from peptide substrates, with a preference for arginine. The purified recombinant Lmo1603 was activated by Fe3+, Zn2+ and Mn2+, but strongly stimulated by Co2+, indicating that Lmo1603 is a cobalt-dependent aminopeptidase. Single mutation at any of the Glu216, Glu281, His308, Tyr315, His327, and Asp329 completely abolished the enzymatic activity of Lmo1603. More importantly, we showed that Lmo1603 was mainly involved in Listeria infection, but not required for growth in rich laboratory medium and minimal defined medium. Disruption of Lmo1603 resulted in almost complete attenuation of Listeria virulence in a mouse infection model. In addition, we demonstrated that Lmo1603 was mainly localized in the bacterial cytosol and required for invasion and survival inside human epithelial cells and murine macrophages. We conclude that Lmo1603 encodes a functional aminopeptidase T of M29 family, which acts as a novel intracellular virulence factor essential in the successful establishment of L. monocytogenes infections in a mouse model.
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Affiliation(s)
- Changyong Cheng
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Xiaowen Wang
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Zhimei Dong
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Chunyan Shao
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Yongchun Yang
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Weihuan Fang
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China.,Zhejiang University Institute of Preventive Veterinary Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang 310058, P. R. China
| | - Chun Fang
- Zhejiang University Institute of Preventive Veterinary Medicine, 866 Yuhangtang Road, Hangzhou, Zhejiang 310058, P. R. China
| | - Hang Wang
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Menghua Yang
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
| | - Lingli Jiang
- Zhoushan Entry-Exit Inspection and Quarantine Bureau, 555 Haijing Road, Zhoushan, Zhejiang 316000, P. R. China
| | - Xiangyang Zhou
- Zhoushan Entry-Exit Inspection and Quarantine Bureau, 555 Haijing Road, Zhoushan, Zhejiang 316000, P. R. China
| | - Houhui Song
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanchengbei Road, Lin'an, Zhejiang 311300, P. R. China
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14
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Fang C, Cao T, Cheng C, Xia Y, Shan Y, Xin Y, Guo N, Li X, Song H, Fang W. Activation of PrfA results in overexpression of virulence factors but does not rescue the pathogenicity of Listeria monocytogenes M7. J Med Microbiol 2015; 64:818-827. [PMID: 26055558 DOI: 10.1099/jmm.0.000101] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Listeria monocytogenes encodes a transcriptional activator, PrfA, to positively regulate the expression of virulence factors. Several mutations in PrfA (PrfA*) have been found to contribute to increased regulatory activity. Here, we describe a strain, M7, containing a PrfA*(G145S) that activates expression of virulence factors but with low pathogenicity. To study this contradictory relationship, we exchanged the prfA genes between strains EGDe and M7 (designated EGDe-prfA(M7) and M7-prfA(EGDe)). The phospholipase B (PlcB) and listeriolysin O (LLO) activities were significantly upregulated in the strain EGDe-prfA(M7) (PrfA*). Constitutive activation of PrfA potentiated virulence of the pathogenic strain EGDe, shown as increased adhesion and invasion as well as enhanced cell-to-cell spread in cultured cell lines. However, the strain M7, though PrfA-activated, had significant defects in these virulence-related phenotypes and low pathogenicity in the murine infection model, as compared with EGDe or EGDe-PrfA(M7). To further uncover the possible mechanisms, we analysed abundance and distributions of InlA, InlB, LLO and ActA proteins, all regulated by PrfA, in EGDe, M7 and their prfA mutants. Western blotting showed that the PrfA-regulated genes of constitutively activated PrfA strains were overexpressed in vitro, while different distributions were observed. In contrast to the virulent strain EGDe-prfA(M7), the majority of InlB in M7 was detected in the culture supernatant and not on the bacterial surface. We suppose that the low virulence of strain M7 is due to its defects in infecting host cells, possibly as a result of failed anchorage on the bacterial cells of surface proteins like InlB, a major protein involved in adhesion and invasion of pathogenic L. monocytogenes strains. Further research is warranted to address why InlB detaches from the bacterial cells of this particular strain.
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Affiliation(s)
- Chun Fang
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Tong Cao
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Changyong Cheng
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanbei Road, Lin'an, Zhejiang, 311300, PR China
| | - Ye Xia
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Ying Shan
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Yongping Xin
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Ningning Guo
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Xiaoliang Li
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
| | - Houhui Song
- College of Animal Science and Technology, Zhejiang A&F University, 88 Huanbei Road, Lin'an, Zhejiang, 311300, PR China
| | - Weihuan Fang
- Zhejiang University Institute of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China., College of Animal Science and Technology, Zhejiang A&F University, 88 Huanbei Road, Lin'an, Zhejiang, 311300, PR China., Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, 388 Yuhangtang Road, Hangzhou, Zhejiang, 310058, PR China
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15
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Cheng C, Yang Y, Dong Z, Wang X, Fang C, Yang M, Sun J, Xiao L, Fang W, Song H. Listeria monocytogenes varies among strains to maintain intracellular pH homeostasis under stresses by different acids as analyzed by a high-throughput microplate-based fluorometry. Front Microbiol 2015; 6:15. [PMID: 25667585 PMCID: PMC4304241 DOI: 10.3389/fmicb.2015.00015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 01/07/2015] [Indexed: 11/16/2022] Open
Abstract
Listeria monocytogenes, a food-borne pathogen, has the capacity to maintain intracellular pH (pHi) homeostasis in acidic environments, but the underlying mechanisms remain elusive. Here, we report a simple microplate-based fluorescent method to determine pHi of listerial cells that were prelabeled with the fluorescent dye carboxyfluorescein diacetate N-succinimidyl ester and subjected to acid stress. We found that L. monocytogenes responds differently among strains toward organic and inorganic acids to maintain pHi homeostasis. The capacity of L. monocytogenes to maintain pHi at extracellular pH 4.5 (pHex) was compromised in the presence of acetic acid and lactic acid, but not by hydrochloric acid and citric acid. Organic acids exhibited more inhibitory effects than hydrochloric acid at certain pH conditions. Furthermore, the virulent stains L. monocytogenes EGDe, 850658 and 10403S was more resistant to acidic stress than the avirulent M7 which showed a defect in maintaining pHi homeostasis. Deletion of sigB, a stress-responsive alternative sigma factor from 10403S, markedly altered intracellular pHi homeostasis, and showed a significant growth and survival defect under acidic conditions. Thus, this work provides new insights into bacterial survival mechanism to acidic stresses.
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Affiliation(s)
- Changyong Cheng
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Yongchun Yang
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Zhimei Dong
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Xiaowen Wang
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Chun Fang
- Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Zhejiang University Institute of Preventive Veterinary Medicine Hangzhou, China
| | - Menghua Yang
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Jing Sun
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Liya Xiao
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
| | - Weihuan Fang
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China ; Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, Zhejiang University Institute of Preventive Veterinary Medicine Hangzhou, China
| | - Houhui Song
- College of Animal Science and Technology, Zhejiang A&F University Lin'an, China
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Ramos S, Chafsey I, Silva N, Hébraud M, Santos H, Capelo-Martinez JL, Poeta P, Igrejas G. Effect of vancomycin on the proteome of the multiresistant Enterococcus faecium SU18 strain. J Proteomics 2015; 113:378-87. [DOI: 10.1016/j.jprot.2014.10.012] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 10/03/2014] [Accepted: 10/20/2014] [Indexed: 11/25/2022]
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17
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Fulde M, Willenborg J, Huber C, Hitzmann A, Willms D, Seitz M, Eisenreich W, Valentin-Weigand P, Goethe R. The arginine-ornithine antiporter ArcD contributes to biological fitness of Streptococcus suis. Front Cell Infect Microbiol 2014; 4:107. [PMID: 25161959 PMCID: PMC4129364 DOI: 10.3389/fcimb.2014.00107] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 07/21/2014] [Indexed: 11/19/2022] Open
Abstract
The arginine-ornithine antiporter (ArcD) is part of the Arginine Deiminase System (ADS), a catabolic, energy-providing pathway found in a variety of different bacterial species, including the porcine zoonotic pathogen Streptococcus suis. The ADS has recently been shown to play a role in the pathogenicity of S. suis, in particular in its survival in host cells. The contribution of arginine and arginine transport mediated by ArcD, however, has yet to be clarified. In the present study, we showed by experiments using [U-13C6]arginine as a tracer molecule that S. suis is auxotrophic for arginine and that bacterial growth depends on the uptake of extracellular arginine. To further study the role of ArcD in arginine metabolism, we generated an arcD-specific mutant strain and characterized its growth compared to the wild-type (WT) strain, a virulent serotype 2 strain. The mutant strain showed a markedly reduced growth in chemically defined media supplemented with arginine when compared to the WT strain, suggesting that ArcD promotes arginine uptake. To further evaluate the in vivo relevance of ArcD, we studied the intracellular bacterial survival of the arcD mutant strain in an epithelial cell culture infection model. The mutant strain was substantially attenuated, and its reduced intracellular survival rate correlated with a lower ability to neutralize the acidified environment. Based on these results, we propose that ArcD, by its function as an arginine-ornithine antiporter, is important for supplying arginine as substrate of the ADS and, thereby, contributes to biological fitness and virulence of S. suis in the host.
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Affiliation(s)
- Marcus Fulde
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany ; Department of Medical Microbiology, Helmholtz Centre for Infection Research (HZI) Braunschweig, Germany
| | - Joerg Willenborg
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany
| | - Claudia Huber
- Lehrstuhl für Biochemie, Technische Universität München Garching, Germany
| | - Angela Hitzmann
- Department of Medical Microbiology, Helmholtz Centre for Infection Research (HZI) Braunschweig, Germany
| | - Daniela Willms
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany
| | - Maren Seitz
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany
| | | | - Peter Valentin-Weigand
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany
| | - Ralph Goethe
- Department of Infectious Diseases, Institute for Microbiology, University of Veterinary Medicine Hannover, Germany
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Cheng C, Chen J, Fang C, Xia Y, Shan Y, Liu Y, Wen G, Song H, Fang W. Listeria monocytogenes aguA1, but not aguA2, encodes a functional agmatine deiminase: biochemical characterization of its catalytic properties and roles in acid tolerance. J Biol Chem 2013; 288:26606-15. [PMID: 23918931 DOI: 10.1074/jbc.m113.477380] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Listeria monocytogenes is adaptable to low pH environments and therefore crosses the intestinal barrier to establish systemic infections. L. monocytogenes aguA1 and aguA2 encode putative agmatine deiminases (AgDIs) AguA1 and AguA2. Transcription of aguA1 and aguA2 was significantly induced at pH 5.0. Deletion of aguA1 significantly impaired its survival both in gastric fluid at pH 2.5 and in mouse stomach, whereas aguA2 deletion did not show significant defect of survival in gastric fluid. With agmatine as the sole substrate, AguA1 expressed in Escherichia coli was optimal at 25 °C and over a wide range of pH from 3.5 to 10.5. Recombinant AguA2 showed no deiminase activity. Site-directed mutagenesis revealed that all nine AguA1 mutants completely lost enzymatic activity. AguA2 acquired AgDI activity only when Cys-157 was mutated to glycine. AguA1 mutation at the same site, G157C, also inactivated the enzyme. Thus, we have discovered Gly-157 as a novel residue other than the known catalytic triad (Cys-His-Glu/Asp) in L. monocytogenes that is critical for enzyme activity. Of the two putative AgDIs, we conclude that only AguA1 functionally participates in the AgDI pathway and mediates acid tolerance in L. monocytogenes.
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Affiliation(s)
- Changyong Cheng
- From the Zhejiang University Institute of Preventive Veterinary Medicine, Zhejiang Provincial Key Laboratory of Preventive Veterinary Medicine, and Key Laboratory of Molecular Animal Nutrition of the Ministry of Education, Hangzhou, Zhejiang 310058, China
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