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Ouyang Z, He W, Jiao M, Yu Q, Guo Y, Refat M, Qin Q, Zhang J, Shi Q, Zheng F, Wen Y. Mechanistic and biophysical characterization of polymyxin resistance response regulator PmrA in Acinetobacter baumannii. Front Microbiol 2024; 15:1293990. [PMID: 38476937 PMCID: PMC10927774 DOI: 10.3389/fmicb.2024.1293990] [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: 09/14/2023] [Accepted: 02/05/2024] [Indexed: 03/14/2024] Open
Abstract
Introduction Acinetobacter baumannii PmrAB is a crucial two-component regulatory system (TCS) that plays a vital role in conferring resistance to polymyxin. PmrA, a response regulator belonging to the OmpR/PhoB family, is composed of a C-terminal DNA-binding effector domain and an N-terminal receiver domain. The receiver domain can be phosphorylated by PmrB, a transmembrane sensor histidine kinase that interacts with PmrA. Once phosphorylated, PmrA undergoes a conformational change, resulting in the formation of a symmetric dimer in the receiver domain. This conformational change facilitates the recognition of promoter DNA by the DNA-binding domain of PmrA, leading to the activation of adaptive responses. Methods X-ray crystallography was carried out to solve the structure of PmrA receiver domain. Electrophoretic mobility shift assay and Isothermal titration calorimetry were recruited to validate the interaction between the recombinant PmrA protein and target DNA. Field-emission scanning electron microscopy (FE-SEM) was employed to characterize the surface morphology of A. baumannii in both the PmrA knockout and mutation strains. Results The receiver domain of PmrA follows the canonical α5β5 response regulator assembly, which undergoes dimerization upon phosphorylation and activation. Beryllium trifluoride is utilized as an aspartate phosphorylation mimic in this process. Mutations involved in phosphorylation and dimerization significantly affected the expression of downstream pmrC and naxD genes. This impact resulted in an enhanced cell surface smoothness with fewer modifications, ultimately contributing to a decrease in colistin (polymyxin E) and polymyxin B resistance. Additionally, a conservative direct-repeat DNA PmrA binding sequence TTTAAGNNNNNTTTAAG was identified at the promoter region of the pmrC and naxD gene. These findings provide structural insights into the PmrA receiver domain and reveal the mechanism of polymyxin resistance, suggesting that PmrA could be a potential drug target to reverse polymyxin resistance in Acinetobacter baumannii.
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Affiliation(s)
- Zhenlin Ouyang
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Wenbo He
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Min Jiao
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Qinyue Yu
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Yucheng Guo
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Moath Refat
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an, China
| | - Qian Qin
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Jiaxin Zhang
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Qindong Shi
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
| | - Fang Zheng
- The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education Health Science Center, Xi'an Jiaotong University, Xi'an, China
| | - Yurong Wen
- Shaanxi Provincial Key Laboratory of Sepsis in Critical Care Medicine, Department of Critical Care Medicine, Center for Microbiome Research of Med-X Institute, The First Affiliated Hospital, Xi'an Jiaotong University, Xi'an, China
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Hong Y, Hu D, Verderosa AD, Qin J, Totsika M, Reeves PR. Repeat-Unit Elongations To Produce Bacterial Complex Long Polysaccharide Chains, an O-Antigen Perspective. EcoSal Plus 2023; 11:eesp00202022. [PMID: 36622162 PMCID: PMC10729934 DOI: 10.1128/ecosalplus.esp-0020-2022] [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: 08/03/2022] [Accepted: 12/02/2022] [Indexed: 01/10/2023]
Abstract
The O-antigen, a long polysaccharide that constitutes the distal part of the outer membrane-anchored lipopolysaccharide, is one of the critical components in the protective outer membrane of Gram-negative bacteria. Most species produce one of the structurally diverse O-antigens, with nearly all the polysaccharide components having complex structures made by the Wzx/Wzy pathway. This pathway produces repeat-units of mostly 3-8 sugars on the cytosolic face of the cytoplasmic membrane that is translocated by Wzx flippase to the periplasmic face and polymerized by Wzy polymerase to give long-chain polysaccharides. The Wzy polymerase is a highly diverse integral membrane protein typically containing 10-14 transmembrane segments. Biochemical evidence confirmed that Wzy polymerase is the sole driver of polymerization, and recent progress also began to demystify its interacting partner, Wzz, shedding some light to speculate how the proteins may operate together during polysaccharide biogenesis. However, our knowledge of how the highly variable Wzy proteins work as part of the O-antigen processing machinery remains poor. Here, we discuss the progress to the current understanding of repeat-unit polymerization and propose an updated model to explain the formation of additional short chain O-antigen polymers found in the lipopolysaccharide of diverse Gram-negative species and their importance in the biosynthetic process.
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Affiliation(s)
- Yaoqin Hong
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
- School of Life and Environmental Sciences, The University of Sydney, Camperdown, New South Wales, Australia
| | - Dalong Hu
- Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
| | - Anthony D. Verderosa
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Jilong Qin
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Makrina Totsika
- Centre for Immunology and Infection Control, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Peter R. Reeves
- School of Life and Environmental Sciences, The University of Sydney, Camperdown, New South Wales, Australia
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Brink KR, Hunt MG, Mu AM, Groszman K, Hoang KV, Lorch KP, Pogostin BH, Gunn JS, Tabor JJ. An E. coli display method for characterization of peptide-sensor kinase interactions. Nat Chem Biol 2023; 19:451-459. [PMID: 36482094 PMCID: PMC10065900 DOI: 10.1038/s41589-022-01207-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2021] [Accepted: 10/10/2022] [Indexed: 12/13/2022]
Abstract
Bacteria use two-component system (TCS) signaling pathways to sense and respond to peptides involved in host defense, quorum sensing and inter-bacterial warfare. However, little is known about the broad peptide-sensing capabilities of TCSs. In this study, we developed an Escherichia coli display method to characterize the effects of human antimicrobial peptides (AMPs) on the pathogenesis-regulating TCS PhoPQ of Salmonella Typhimurium with much higher throughput than previously possible. We found that PhoPQ senses AMPs with diverse sequences, structures and biological functions. We further combined thousands of displayed AMP variants with machine learning to identify peptide sub-domains and biophysical features linked to PhoPQ activation. Most of the newfound AMP activators induce PhoPQ in S. Typhimurium, suggesting possible roles in virulence regulation. Finally, we present evidence that PhoPQ peptide-sensing specificity has evolved across commensal and pathogenic bacteria. Our method enables new insights into the specificities, mechanisms and evolutionary dynamics of TCS-mediated peptide sensing in bacteria.
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Affiliation(s)
- Kathryn R Brink
- Ph.D. Program in Systems, Synthetic, and Physical Biology, Rice University, Houston, TX, USA
| | - Maxwell G Hunt
- Ph.D. Program in Systems, Synthetic, and Physical Biology, Rice University, Houston, TX, USA
| | - Andrew M Mu
- Department of Biosciences, Rice University, Houston, TX, USA
| | - Ken Groszman
- Operations Research Center, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ky V Hoang
- Center for Microbial Pathogenesis, Nationwide Children's Hospital, Columbus, OH, USA
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
| | - Kevin P Lorch
- Department of Bioengineering, Rice University, Houston, TX, USA
| | | | - John S Gunn
- Center for Microbial Pathogenesis, Nationwide Children's Hospital, Columbus, OH, USA
- Infectious Diseases Institute, The Ohio State University, Columbus, OH, USA
- Department of Pediatrics, The Ohio State University College of Medicine, Columbus, OH, USA
| | - Jeffrey J Tabor
- Ph.D. Program in Systems, Synthetic, and Physical Biology, Rice University, Houston, TX, USA.
- Department of Biosciences, Rice University, Houston, TX, USA.
- Department of Bioengineering, Rice University, Houston, TX, USA.
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Manieri FZ, Moreira CG. Salmonella Typhimurium O-antigen and VisP play an important role in swarming and osmotic stress response during intracellular conditions. Braz J Microbiol 2022; 53:557-564. [PMID: 35303296 PMCID: PMC9151935 DOI: 10.1007/s42770-022-00701-9] [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: 04/30/2021] [Accepted: 02/01/2022] [Indexed: 02/01/2023] Open
Abstract
Salmonella Typhimurium is a pathogen of clinical relevance and a model of study in host-pathogen interactions. The virulence and stress-related periplasmic protein VisP is important during S. Typhimurium pathogenesis. It supports bacteria invading host cells, surviving inside macrophages, swimming, and succeeding in murine colitis model, O-antigen assembly, and responding to cationic antimicrobial peptides. This study aimed to investigate the role of the O-antigen molecular ruler WzzST and the periplasmic protein VisP in swarming motility and osmotic stress response. Lambda red mutagenesis was performed to generate single and double mutants, followed by swarming motility, qRT-PCR, Western blot, and growth curves. Here we demonstrate that the deletion of visP affects swarming under osmotic stress and changes the expression levels of genes responsible for chemotaxis, flagella assembly, and general stress response. The deletion of the gene encoding for the O-antigen co-polymerase wzzST increases swarming motility but not under osmotic stress. A second mutation in O-antigen co-polymerase wzzST in a ΔvisP background affected gene expression levels. The ΔvisP growth was affected by sodium and magnesium levels on N-minimum media. These data indicate that WzzST has a role in swarming the motility of S. Typhimurium, as the VisP is involved in chemotaxis and osmotic stress, specifically in response to MgCl2 and NaCl.
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Affiliation(s)
- Fernanda Z Manieri
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University, Rodovia Araraquara-Jau, km 1, s/n, Araraquara, São Paulo, 14800-903, Brazil
| | - Cristiano G Moreira
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University, Rodovia Araraquara-Jau, km 1, s/n, Araraquara, São Paulo, 14800-903, Brazil.
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Liu B, Qian C, Wu P, Li X, Liu Y, Mu H, Huang M, Zhang Y, Jia T, Wang Y, Wang L, Zhang X, Huang D, Yang B, Feng L, Wang L. Attachment of Enterohemorrhagic Escherichia coli to Host Cells Reduces O Antigen Chain Length at the Infection Site That Promotes Infection. mBio 2021; 12:e0269221. [PMID: 34903041 PMCID: PMC8669466 DOI: 10.1128/mbio.02692-21] [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: 09/11/2021] [Accepted: 11/15/2021] [Indexed: 11/20/2022] Open
Abstract
Many enteropathogenic bacteria express a needle-like type III secretion system (T3SS) that translocates effectors into host cells promoting infection. O antigen (OAg) constitutes the outer layer of Gram-negative bacteria protecting bacteria from host immune responses. Shigella constitutively shortens the OAg molecule in its three-dimensional conformation by glucosylation, leading to enhanced T3SS function. However, whether and how other enteropathogenic bacteria shorten the OAg molecule that probably facilitates infection remain unknown. For the first time, we report a smart mechanism by which enterohemorrhagic Escherichia coli specifically reduces the size of the OAg molecule at the infection site upon sensing mechanical signals of intestinal epithelial cell attachment via the membrane protein YgjI. YgjI represses expression of the OAg chain length regulator gene fepE via the global regulator H-NS, leading to shortened OAg chains and injection of more T3SS effectors into host cells. However, bacteria express long-chain OAg in the intestinal lumen benefiting their survival. Animal experiments show that blocking this regulatory pathway significantly attenuates bacterial virulence. This finding enhances our understanding of interactions between the surfaces of bacterial and host cells and the way this interaction enhances bacterial pathogenesis. IMPORTANCE Little is known about the regulation of cell wall structure of enteropathogenic bacteria within the host. Here, we report that enterohemorrhagic Escherichia coli regulates its cell wall structure during the infection process, which balances its survival in the intestinal lumen and infection of intestinal epithelial cells. In the intestinal lumen, bacteria express long-chain OAg, which is located in the outer part of the cell wall, leading to enhanced resistance to antimicrobial peptides. However, upon epithelial cell attachment, bacteria sense this mechanical signal via a membrane protein and reduce the OAg chain length, resulting in enhanced injection into epithelial cells of T3SS effectors that mediate host cell infection. Similar regulation mechanisms of cell wall structure in response to host cell attachment may be widespread in pathogenic bacteria and closely related with bacterial pathogenesis.
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Affiliation(s)
- Bin Liu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
- The Institute of Translational Medicine Research, Tianjin Union Medical Center, Nankai University Affiliated Hospital, Nankai University, Tianjin, People’s Republic of China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, People’s Republic of China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, People’s Republic of China
| | - Chengqian Qian
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Pan Wu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Xiaodan Li
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Yutao Liu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Huiqian Mu
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Min Huang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Yang Zhang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Tianyuan Jia
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Yuanyuan Wang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Lu Wang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Xiao Zhang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Di Huang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Bin Yang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
| | - Lu Feng
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, People’s Republic of China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, People’s Republic of China
| | - Lei Wang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, People’s Republic of China
- The Institute of Translational Medicine Research, Tianjin Union Medical Center, Nankai University Affiliated Hospital, Nankai University, Tianjin, People’s Republic of China
- The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, People’s Republic of China
- Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, People’s Republic of China
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, People’s Republic of China
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Shprung T, Wani NA, Wilmes M, Mangoni ML, Bitler A, Shimoni E, Sahl HG, Shai Y. Opposing Effects of PhoPQ and PmrAB on the Properties of Salmonella enterica serovar Typhimurium: Implications on Resistance to Antimicrobial Peptides. Biochemistry 2021; 60:2943-2955. [PMID: 34547893 PMCID: PMC8638962 DOI: 10.1021/acs.biochem.1c00287] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The increasing number of resistant
bacteria is a major threat worldwide,
leading to the search for new antibiotic agents. One of the leading
strategies is the use of antimicrobial peptides (AMPs), cationic and
hydrophobic innate immune defense peptides. A major target of AMPs
is the bacterial membrane. Notably, accumulating data suggest that
AMPs can activate the two-component systems (TCSs) of Gram-negative
bacteria. These include PhoP-PhoQ (PhoPQ) and PmrA-PmrB (PmrAB), responsible
for remodeling of the bacterial cell surface. To better understand
this mechanism, we utilized bacteria deficient either in one system
alone or in both and biophysical tools including fluorescence spectroscopy,
single-cell atomic force microscopy, electron microscopy, and mass
spectrometry (MoskowitzS. M.;2012, 56, 1019−103022106224; ChengH. Y.;2010, 17, 6020653976). Our data suggested that the two systems have opposing
effects on the properties of Salmonella enterica. The knockout of PhoPQ made the bacteria more susceptible to AMPs
by making the surface less rigid, more polarized, and permeable with
a slightly more negatively charged cell wall. In addition, the periplasmic
space is thinner. In contrast, the knockout of PmrAB did not affect
its susceptibility, while it made the bacterial outer layer very rigid,
less polarized, and less permeable than the other two mutants, with
a negatively charged cell wall similar to the WT. Overall, the data
suggest that the coexistence of systems with opposing effects on the
biophysical properties of the bacteria contribute to their membrane
flexibility, which, on the one hand, is important to accommodate changing
environments and, on the other hand, may inhibit the development of
meaningful resistance to AMPs.
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Affiliation(s)
- Tal Shprung
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Naiem Ahmad Wani
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Miriam Wilmes
- Pharmaceutical Microbiology Section, Institute for Medical Microbiology, Immunology and Parasitology, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
| | - Maria Luisa Mangoni
- Department of Biochemical Sciences A. Rossi Fanelli, Faculty of Pharmacy and Medicine, Sapienza University of Rome, CU27, 00185 Roma, Italy
| | - Arkadi Bitler
- Department of Chemical Research Support, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eyal Shimoni
- Department of Chemical Research Support, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Hans-Georg Sahl
- Pharmaceutical Microbiology Section, Institute for Medical Microbiology, Immunology and Parasitology, University of Bonn, Sigmund-Freud-Strasse 25, D-53127 Bonn, Germany
| | - Yechiel Shai
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
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Tian X, Manat G, Gasiorowski E, Auger R, Hicham S, Mengin-Lecreulx D, Boneca IG, Touzé T. LpxT-Dependent Phosphorylation of Lipid A in Escherichia coli Increases Resistance to Deoxycholate and Enhances Gut Colonization. Front Microbiol 2021; 12:676596. [PMID: 34017319 PMCID: PMC8129183 DOI: 10.3389/fmicb.2021.676596] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Accepted: 04/09/2021] [Indexed: 11/13/2022] Open
Abstract
The cell surface of Gram-negative bacteria usually exhibits a net negative charge mostly conferred by lipopolysaccharides (LPS). This property sensitizes bacterial cells to cationic antimicrobial peptides, such as polymyxin B, by favoring their binding to the cell surface. Gram-negative bacteria can modify their surface to counteract these compounds such as the decoration of their LPS by positively charged groups. For example, in Escherichia coli and Salmonella, EptA and ArnT add amine-containing groups to the lipid A moiety. In contrast, LpxT enhances the net negative charge by catalyzing the synthesis of tri-phosphorylated lipid A, whose function is yet unknown. Here, we report that E. coli has the intrinsic ability to resist polymyxin B upon the simultaneous activation of the two component regulatory systems PhoPQ and PmrAB by intricate environmental cues. Among many LPS modifications, only EptA- and ArnT-dependent decorations were required for polymyxin B resistance. Conversely, the acquisition of polymyxin B resistance compromised the innate resistance of E. coli to deoxycholate, a major component of bile. The inhibition of LpxT by PmrR, under PmrAB-inducing conditions, specifically accounted for the acquired susceptibility to deoxycholate. We also report that the kinetics of intestinal colonization by the E. coli lpxT mutant was impaired as compared to wild-type in a mouse model of infection and that lpxT was upregulated at the temperature of the host. Together, these findings highlight an important function of LpxT and suggest that a tight equilibrium between EptA- and LpxT-dependent decorations, which occur at the same position of lipid A, is critical for the life style of E. coli.
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Affiliation(s)
- Xudong Tian
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Guillaume Manat
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Elise Gasiorowski
- Institut Pasteur, Unité Biologie et Génétique de la Paroi Bactérienne, Paris, France.,Université de Paris, Sorbonne Paris Cité, Paris, France
| | - Rodolphe Auger
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Samia Hicham
- Institut Pasteur, Unité Biologie et Génétique de la Paroi Bactérienne, Paris, France
| | - Dominique Mengin-Lecreulx
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Ivo Gomperts Boneca
- Institut Pasteur, Unité Biologie et Génétique de la Paroi Bactérienne, Paris, France
| | - Thierry Touzé
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
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Whitfield C, Williams DM, Kelly SD. Lipopolysaccharide O-antigens-bacterial glycans made to measure. J Biol Chem 2020; 295:10593-10609. [PMID: 32424042 DOI: 10.1074/jbc.rev120.009402] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Revised: 05/17/2020] [Indexed: 01/05/2023] Open
Abstract
Lipopolysaccharides are critical components of bacterial outer membranes. The more conserved lipid A part of the lipopolysaccharide molecule is a major element in the permeability barrier imposed by the outer membrane and offers a pathogen-associated molecular pattern recognized by innate immune systems. In contrast, the long-chain O-antigen polysaccharide (O-PS) shows remarkable structural diversity and fulfills a range of functions, depending on bacterial lifestyles. O-PS production is vital for the success of clinically important Gram-negative pathogens. The biological properties and functions of O-PSs are mostly independent of specific structures, but the size distribution of O-PS chains is particularly important in many contexts. Despite the vast O-PS chemical diversity, most are produced in bacterial cells by two assembly strategies, and the different mechanisms employed in these pathways to regulate chain-length distribution are emerging. Here, we review our current understanding of the mechanisms involved in regulating O-PS chain-length distribution and discuss their impact on microbial cell biology.
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Affiliation(s)
- Chris Whitfield
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Danielle M Williams
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
| | - Steven D Kelly
- Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario, Canada
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Abstract
Detection of mucoid Pseudomonas aeruginosa, characterized by the overproduction of alginate, is correlated with the establishment of a chronic pulmonary infection and disease progression in people with cystic fibrosis (CF). In addition to the overproduction of alginate, loss of O antigen lipopolysaccharide production is also selected for in chronic infection isolates. In this study, we have identified the regulatory network that inversely regulates O antigen and alginate production. Understanding the regulation of these chronic phenotypes will elucidate mechanisms that are important for the establishment of a long-term P. aeruginosa lung infection and ultimately provide an opportunity for intervention. Preventing P. aeruginosa from chronically adapting to the CF lung environment could provide a better outcome for people who are infected. Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic lung infections in people with cystic fibrosis (CF). Chronic P. aeruginosa isolates generally do not express O antigen and often have a mucoid phenotype, which is characterized by the overproduction of the exopolysaccharide alginate. Therefore, O antigen expression and the mucoid phenotype may be coordinately regulated upon chronic adaption to the CF lung. Here we demonstrate that PDO300, a mucoid strain derived from the nonmucoid laboratory isolate PAO1, does not produce very long O antigen due to decreased expression of Wzz2, the very long O antigen chain length control protein, and that mucoid clinical isolates express reduced levels of Wzz2 compared to nonmucoid isolates. Further, we show that forcing the expression of very long O antigen by PDO300, by providing wzz2 in trans, does not alter alginate production, suggesting that sugar precursors are not limited between the two biosynthesis pathways. Moreover, we confirm that AmrZ, a transcription factor highly expressed in mucoid strains, is a negative regulator of wzz2 promoter activity and very long O antigen expression. These experiments identify the first transcriptional regulator of O antigen chain length in P. aeruginosa and support a model where transition to a chronic mucoid phenotype is correlated with downregulation of very long O antigen through decreased Wzz2 production.
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Contribution of Novel Amino Acid Alterations in PmrA or PmrB to Colistin Resistance in mcr-Negative Escherichia coli Clinical Isolates, Including Major Multidrug-Resistant Lineages O25b:H4-ST131- H30Rx and Non-x. Antimicrob Agents Chemother 2018; 62:AAC.00864-18. [PMID: 29914952 DOI: 10.1128/aac.00864-18] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Accepted: 06/02/2018] [Indexed: 11/20/2022] Open
Abstract
Colistin is a last-line drug for multidrug-resistant Gram-negative bacteria. We previously reported four plasmid-mediated colistin resistance (mcr) gene-negative colistin-resistant Escherichia coli clinical isolates, including the major pathogenic and fluoroquinolone-resistant strains O25b:H4-ST131-H30Rx (isolates SRE34 and SRE44; MIC for colistin = 16 mg/liter), non-x (SME296; MIC = 8 mg/liter), and O18-ST416 (SME222; MIC = 4 mg/liter). In this study, we investigated the colistin resistance mechanism and identified novel amino acid substitutions or deletions in the PmrAB two-component system that activates eptA (encoding a phosphoethanolamine transferase) and arnT (encoding an undecaprenyl phosphate-alpha-4-amino-4-deoxy-l-arabinose arabinosyl transferase) in all colistin-resistant isolates. SRE34 possessed deletion Δ27-45 (LISVFWLWHESTEQIQLFE) in PmrB, SRE44 possessed substitution L105P in PmrA, and both SME222 and SME296 included substitution G206D in PmrB. Matrix-assisted laser desorption ionization-time of flight mass spectrometry revealed that lipid A is modified with phosphoethanolamine in all four isolates. Deletion of pmrAB decreased colistin MICs to 0.5 mg/liter and lowered eptA and arnT expression. Chromosomal replacement of mutated pmrA or pmrB in colistin-susceptible O25b:H4-ST131 strain SME98 (colistin MIC = 0.5 mg/liter) increased the colistin MIC to that of the respective parent colistin-resistant isolate. In addition, SME98 mutants in which pmrAB was replaced with mutated pmrAB showed no significant differences in bacterial growth and competition culture from the parent strain, except for the mutant with L105P in PmrA, whose growth was significantly suppressed in the presence of the parent strain. In conclusion, some O25b:H4-ST131 strains appear to acquire colistin resistance via phosphoethanolamine modification of lipid A through amino acid changes in PmrAB, and the amino acid changes in PmrB do not influence bacterial growth.
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Trimble MJ, Mlynárčik P, Kolář M, Hancock REW. Polymyxin: Alternative Mechanisms of Action and Resistance. Cold Spring Harb Perspect Med 2016; 6:cshperspect.a025288. [PMID: 27503996 DOI: 10.1101/cshperspect.a025288] [Citation(s) in RCA: 254] [Impact Index Per Article: 31.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Antibiotic resistance among pathogenic bacteria is an ever-increasing issue worldwide. Unfortunately, very little has been achieved in the pharmaceutical industry to combat this problem. This has led researchers and the medical field to revisit past drugs that were deemed too toxic for clinical use. In particular, the cyclic cationic peptides polymyxin B and colistin, which are specific for Gram-negative bacteria, have been used as "last resort" antimicrobials. Before the 1980s, these drugs were known for their renal and neural toxicities; however, new clinical practices and possibly improved manufacturing have made them safer to use. Previously suggested to primarily attack the membranes of Gram-negative bacteria and to not easily select for resistant mutants, recent research exploring resistance and mechanisms of action has provided new perspectives. This review focuses primarily on the proposed alternative mechanisms of action, known resistance mechanisms, and how these support the alternative mechanisms of action.
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Affiliation(s)
- Michael J Trimble
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Patrik Mlynárčik
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Milan Kolář
- Department of Microbiology, Faculty of Medicine and Dentistry, Palacký University, 771 47 Olomouc, Czech Republic
| | - Robert E W Hancock
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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An Amphipathic Undecapeptide with All d-Amino Acids Shows Promising Activity against Colistin-Resistant Strains of Acinetobacter baumannii and a Dual Mode of Action. Antimicrob Agents Chemother 2015; 60:592-9. [PMID: 26574005 DOI: 10.1128/aac.01966-15] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 11/08/2015] [Indexed: 11/20/2022] Open
Abstract
Multiple strains of Acinetobacter baumannii have developed multidrug resistance (MDR), leaving colistin as the only effective treatment. The cecropin-α-melittin hybrid BP100 (KKLFKKILKYL-NH2) and its analogs have previously shown activity against a wide array of plant and human pathogens. In this study, we investigated the in vitro antibacterial activities of 18 BP100 analogs (four known and 14 new) against the MDR A. baumannii strain ATCC BAA-1605, as well as against a number of other clinically relevant human pathogens. Selected peptides were further evaluated against strains of A. baumannii that acquired resistance to colistin due to mutations of the lpxC, lpxD, pmrA, and pmrB genes. The novel analogue BP214 showed antimicrobial activity at 1 to 2 μM and a hemolytic 50% effective concentration (EC50) of >150 μM. The lower activity of its enantiomer suggests a dual, specific and nonspecific mode of action. Interestingly, colistin behaved antagonistically to BP214 when pmrAB and lpxC mutants were challenged.
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Nuri R, Shprung T, Shai Y. Defensive remodeling: How bacterial surface properties and biofilm formation promote resistance to antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3089-100. [PMID: 26051126 DOI: 10.1016/j.bbamem.2015.05.022] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 05/25/2015] [Accepted: 05/26/2015] [Indexed: 11/15/2022]
Abstract
Multidrug resistance bacteria are a major concern worldwide. These pathogens cannot be treated with conventional antibiotics and thus alternative therapeutic agents are needed. Antimicrobial peptides (AMPs) are considered to be good candidates for this purpose. Most AMPs are short and positively charged amphipathic peptides, which are found in all known forms of life. AMPs are known to kill bacteria by binding to the negatively charged bacterial surface, and in most cases cause membrane disruption. Resistance toward AMPs can be developed, by modification of bacterial surface molecules, secretion of protective material and up-regulation or elimination of specific proteins. Because of the general mechanisms of attachment and action of AMPs, bacterial resistance to AMPs often involves biophysical and biochemical changes such as surface rigidity, cell wall thickness, surface charge, as well as membrane and cell wall modification. Here we focus on the biophysical, surface and surrounding changes that bacteria undergo in acquiring resistance to AMPs. In addition we discuss the question of whether bacterial resistance to administered AMPs might compromise our innate immunity to endogenous AMPs. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
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Affiliation(s)
- Reut Nuri
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Tal Shprung
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yechiel Shai
- Department of Biological Chemistry, The Weizmann Institute of Science, Rehovot 76100, Israel.
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Matamouros S, Miller SI. S. Typhimurium strategies to resist killing by cationic antimicrobial peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3021-5. [PMID: 25644871 DOI: 10.1016/j.bbamem.2015.01.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 01/18/2015] [Accepted: 01/21/2015] [Indexed: 01/08/2023]
Abstract
S. Typhimurium is a broad host range Gram-negative pathogen that must evade killing by host innate immune systems to colonize, replicate, cause disease, and be transmitted to other hosts. A major pathogenic strategy of Salmonellae is entrance, survival, and replication within eukaryotic cell phagocytic vacuoles. These phagocytic vacuoles and gastrointestinal mucosal surfaces contain multiple cationic antimicrobial peptides (CAMPs) which control invading bacteria. S. Typhimurium possesses several key mechanisms to resist killing by CAMPs which involve sensing CAMPs and membrane damage to activate signaling cascades that result in remodeling of the bacterial envelope to reduce its overall negative charge with an increase in hydrophobicity to decrease binding and effectiveness of CAMPs. Moreover Salmonellae have additional mechanisms to resist killing by CAMPs including an outer membrane protease which targets cationic peptides at the surface, and specific efflux pumps which protect the inner membrane from damage. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
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Affiliation(s)
- Susana Matamouros
- Departments of Microbiology, University of Washington, Seattle, WA 98195, USA
| | - Samuel I Miller
- Departments of Microbiology, University of Washington, Seattle, WA 98195, USA; Departments of Genome Sciences, University of Washington, Seattle, WA 98195, USA; Department of Medicine, University of Washington, Seattle, WA 98195, USA.
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Antibacterial mechanisms of polymyxin and bacterial resistance. BIOMED RESEARCH INTERNATIONAL 2015; 2015:679109. [PMID: 25664322 PMCID: PMC4312571 DOI: 10.1155/2015/679109] [Citation(s) in RCA: 142] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Accepted: 11/10/2014] [Indexed: 11/18/2022]
Abstract
Multidrug resistance in pathogens is an increasingly significant threat for human health. Indeed, some strains are resistant to almost all currently available antibiotics, leaving very limited choices for antimicrobial clinical therapy. In many such cases, polymyxins are the last option available, although their use increases the risk of developing resistant strains. This review mainly aims to discuss advances in unraveling the mechanisms of antibacterial activity of polymyxins and bacterial tolerance together with the description of polymyxin structure, synthesis, and structural modification. These are expected to help researchers not only develop a series of new polymyxin derivatives necessary for future medical care, but also optimize the clinical use of polymyxins with minimal resistance development.
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Molina L, Udaondo Z, Duque E, Fernández M, Molina-Santiago C, Roca A, Porcel M, de la Torre J, Segura A, Plesiat P, Jeannot K, Ramos JL. Antibiotic resistance determinants in a Pseudomonas putida strain isolated from a hospital. PLoS One 2014; 9:e81604. [PMID: 24465371 PMCID: PMC3894933 DOI: 10.1371/journal.pone.0081604] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2013] [Accepted: 10/15/2013] [Indexed: 12/31/2022] Open
Abstract
Environmental microbes harbor an enormous pool of antibiotic and biocide resistance genes that can impact the resistance profiles of animal and human pathogens via horizontal gene transfer. Pseudomonas putida strains are ubiquitous in soil and water but have been seldom isolated from humans. We have established a collection of P. putida strains isolated from in-patients in different hospitals in France. One of the isolated strains (HB3267) kills insects and is resistant to the majority of the antibiotics used in laboratories and hospitals, including aminoglycosides, ß-lactams, cationic peptides, chromoprotein enediyne antibiotics, dihydrofolate reductase inhibitors, fluoroquinolones and quinolones, glycopeptide antibiotics, macrolides, polyketides and sulfonamides. Similar to other P. putida clinical isolates the strain was sensitive to amikacin. To shed light on the broad pattern of antibiotic resistance, which is rarely found in clinical isolates of this species, the genome of this strain was sequenced and analysed. The study revealed that the determinants of multiple resistance are both chromosomally-borne as well as located on the pPC9 plasmid. Further analysis indicated that pPC9 has recruited antibiotic and biocide resistance genes from environmental microorganisms as well as from opportunistic and true human pathogens. The pPC9 plasmid is not self-transmissible, but can be mobilized by other bacterial plasmids making it capable of spreading antibiotic resistant determinants to new hosts.
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Affiliation(s)
- Lázaro Molina
- Laboratorio de Investigación y Control Agroalimentario, Universidad de Huelva, Huelva, Spain
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
- Centro de Investigación en Química Sostenible, Universidad de Huelva, Huelva, Spain
| | - Zulema Udaondo
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Estrella Duque
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | | | - Carlos Molina-Santiago
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Amalia Roca
- Bio-Iliberis Research and Development, Peligros-Granada, Spain
| | - Mario Porcel
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Jesús de la Torre
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Ana Segura
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
| | - Patrick Plesiat
- Centre Hospitalier Régional Universitaire - Hôpital Jean Minjoz, Besançon, France
| | - Katy Jeannot
- Centre Hospitalier Régional Universitaire - Hôpital Jean Minjoz, Besançon, France
| | - Juan-Luis Ramos
- Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain
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Chen HD, Groisman EA. The biology of the PmrA/PmrB two-component system: the major regulator of lipopolysaccharide modifications. Annu Rev Microbiol 2013; 67:83-112. [PMID: 23799815 DOI: 10.1146/annurev-micro-092412-155751] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The ability of gram-negative bacteria to resist killing by antimicrobial agents and to avoid detection by host immune systems often entails modification to the lipopolysaccharide (LPS) in their outer membrane. In this review, we examine the biology of the PmrA/PmrB two-component system, the major regulator of LPS modifications in the enteric pathogen Salmonella enterica. We examine the signals that activate the sensor PmrB and the targets controlled by the transcriptional regulator PmrA. We discuss the PmrA/PmrB-dependent chemical decorations of the LPS and their role in resistance to antibacterial agents. We analyze the feedback mechanisms that modulate the activity and thus output of the PmrA/PmrB system, dictating when, where, and to what extent bacteria modify their LPS. Finally, we explore the qualitative and quantitative differences in gene expression outputs resulting from the distinct PmrA/PmrB circuit architectures in closely related bacteria, which may account for their differential survival in various ecological niches.
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May JF, Groisman EA. Conflicting roles for a cell surface modification in Salmonella. Mol Microbiol 2013; 88:970-83. [PMID: 23646936 DOI: 10.1111/mmi.12236] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/12/2013] [Indexed: 12/15/2022]
Abstract
Chemical modifications of components of the bacterial cell envelope can enhance resistance to antimicrobial agents. Why then are such modifications produced only under specific conditions? Here, we address this question by examining the role of regulated variations in O-antigen length in the lipopolysaccharide (LPS), a glycolipid that forms most of the outer leaflet of the outer membrane in Gram-negative bacteria. We determined that activation of the PmrA/PmrB two-component system, which is the major regulator of LPS alterations in Salmonella enterica serovar Typhimurium, impaired growth of Salmonella in bile. This growth defect required the PmrA-activated gene wzz(st), which encodes the protein that determines long O-antigen chain length and confers resistance to complement-mediated killing. By contrast, this growth defect did not require the wzz(fepE) gene, which controls production of very long O-antigen, or other PmrA-activated genes that mediate modifications of lipid A or core regions of the LPS. Additionally, we establish that long O-antigen inhibits growth in bile only in the presence of enterobacterial common antigen, an outer-membrane glycolipid that contributes to bile resistance. Our results suggest that Salmonella regulates the proportion of long O-antigen in its LPS to respond to the different conditions it faces during infection.
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Affiliation(s)
- John F May
- Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06536, USA
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Farizano JV, Pescaretti MDLM, López FE, Hsu FF, Delgado MA. The PmrAB system-inducing conditions control both lipid A remodeling and O-antigen length distribution, influencing the Salmonella Typhimurium-host interactions. J Biol Chem 2012; 287:38778-89. [PMID: 23019341 DOI: 10.1074/jbc.m112.397414] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The Salmonella enterica serovar Typhimurium lipopolysaccharide consisting of covalently linked lipid A, non-repeating core oligosaccharide, and the O-antigen polysaccharide is the most exposed component of the cell envelope. Previous studies demonstrated that all of these regions act against the host immunity barrier. The aim of this study was to define the role and interaction of PmrAB-dependent gene products required for the lipopolysaccharide component synthesis or modification mainly during the Salmonella infection. The PmrAB two-component system activation promotes a remodeling of lipid A and the core region by addition of 4-aminoarabinose and/or phosphoethanolamine. These PmrA-dependent activities are produced by activation of ugd, pbgPE, pmrC, cpta, and pmrG transcription. In addition, under PmrA regulator activation, the expression of wzz(fepE) and wzz(st) genes is induced, and their products are required to determine the O-antigen chain length. Here we report for the first time that Wzz(st) protein is necessary to maintain the balance of 4-aminoarabinose and phosphoethanolamine lipid A modifications. Moreover, we demonstrate that the interaction of the PmrA-dependent pbgE(2) and pbgE(3) gene products is important for the formation of the short O-antigen region. Our results establish that PmrAB is the global regulatory system that controls lipopolysaccharide modification, leading to a coordinate regulation of 4-aminoarabinose incorporation and O-antigen chain length to respond against the host defense mechanisms.
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Affiliation(s)
- Juan V Farizano
- Instituto Superior de Investigaciones Biológicas, Consejo Nacional de Investigaciones Científicas y Técnicas-Universidad Nacional de Tucumán, 4000 San Miguel de Tucumán, Tucumán, Argentina
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Kato A, Chen HD, Latifi T, Groisman EA. Reciprocal control between a bacterium's regulatory system and the modification status of its lipopolysaccharide. Mol Cell 2012; 47:897-908. [PMID: 22921935 DOI: 10.1016/j.molcel.2012.07.017] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2011] [Revised: 06/18/2012] [Accepted: 07/14/2012] [Indexed: 01/29/2023]
Abstract
Gram-negative bacteria often modify their lipopolysaccharide (LPS), thereby increasing resistance to antimicrobial agents and avoidance of the host immune system. However, it is unclear how bacteria adjust the levels and activities of LPS-modifying enzymes in response to the modification status of their LPS. We now address this question by investigating the major regulator of LPS modifications in Salmonella enterica. We report that the PmrA/PmrB system controls expression of a membrane peptide that inhibits the activity of LpxT, an enzyme responsible for increasing the LPS negative charge. LpxT's inhibition and the PmrA-dependent incorporation of positively charged L-4-aminoarabinose into the LPS decrease Fe(3+) binding to the bacterial cell. Because Fe(3+) is an activating ligand for the sensor PmrB, transcription of PmrA-dependent LPS-modifying genes is reduced. This mechanism enables bacteria to sense their cell surface by its effect on the availability of an inducing signal for the system regulating cell-surface modifications.
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Affiliation(s)
- Akinori Kato
- Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO 63110, USA
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Cota I, Blanc-Potard AB, Casadesús J. STM2209-STM2208 (opvAB): a phase variation locus of Salmonella enterica involved in control of O-antigen chain length. PLoS One 2012; 7:e36863. [PMID: 22606300 PMCID: PMC3350482 DOI: 10.1371/journal.pone.0036863] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 04/15/2012] [Indexed: 11/18/2022] Open
Abstract
STM2209 and STM2208 are contiguous loci annotated as putative protein-coding genes in the chromosome of Salmonella enterica. Lack of homologs in related Enterobacteria and low G+C content suggest that S. enterica may have acquired STM2209-STM2208 by horizontal transfer. STM2209 and STM2208 are co-transcribed from a promoter upstream STM2209, and their products are inner (cytoplasmic) membrane proteins. Analysis with the bacterial adenylate cyclase two-hybrid system suggests that STM2209 and STM2208 may interact. Expression of STM2209-STM2208 is subjected to phase variation in wild type Salmonella enterica serovar Typhimurium. Switching frequencies in LB medium are 6.1×10−5 (OFF→ON) and 3.7×10−2 (ON→OFF) per cell and generation. Lack of DNA adenine methylation locks STM2209-STM2208 in the ON state, and lack of the LysR-type factor OxyR locks STM2209-STM2208 in the OFF state. OxyR-dependent activation of STM2209-STM2208 expression is independent of the oxidation state of OxyR. Salmonella cultures locked in the ON state show alteration of O-antigen length in the lipopolysaccharide, reduced absorption of bacteriophage P22, impaired resistance to serum, and reduced proliferation in macrophages. Phenotypic heterogeneity generated by STM2209-STM2208 phase variation may thus provide defense against phages. In turn, formation of a subpopulation unable to proliferate in macrophages may restrain Salmonella spread in animal organs, potentially contributing to successful infection.
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Affiliation(s)
- Ignacio Cota
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
| | - Anne Béatrice Blanc-Potard
- Unité Mixte de Recherches 5235, Centre National de la Recherche Scientifique et Université Montpellier II, Montpellier, France
| | - Josep Casadesús
- Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain
- * E-mail:
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