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Li Z, Zhu Y, Zhang W, Mu W. Rcs signal transduction system in Escherichia coli: Composition, related functions, regulatory mechanism, and applications. Microbiol Res 2024; 285:127783. [PMID: 38795407 DOI: 10.1016/j.micres.2024.127783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Revised: 05/20/2024] [Accepted: 05/22/2024] [Indexed: 05/28/2024]
Abstract
The regulator of capsule synthesis (Rcs) system, an atypical two-component system prevalent in numerous gram-negative bacteria, serves as a sophisticated regulatory phosphorylation cascade mechanism. It plays a pivotal role in perceiving environmental stress and regulating the expression of downstream genes to ensure host survival. During the signaling transduction process, various proteins participate in phosphorylation to further modulate signal inputs and outputs. Although the structure of core proteins related to the Rcs system has been partially well-defined, and two models have been proposed to elucidate the intricate molecular mechanisms underlying signal sensing, a systematic characterization of the signal transduction process of the Rcs system remains challenging. Furthermore, exploring its corresponding regulator outputs is also unremitting. This review aimed to shed light on the regulation of bacterial virulence by the Rcs system. Moreover, with the assistance of the Rcs system, biosynthesis technology has developed high-value target production. Additionally, via this review, we propose designing chimeric Rcs biosensor systems to expand their application as synthesis tools. Finally, unsolved challenges are highlighted to provide the basic direction for future development of the Rcs system.
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Affiliation(s)
- Zeyu Li
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Yingying Zhu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Wenli Zhang
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China
| | - Wanmeng Mu
- State Key Laboratory of Food Science and Resources, Jiangnan University, Wuxi, Jiangsu 214122, China.
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Harshaw NS, Meyer MD, Stella NA, Lehner KM, Kowalski RP, Shanks RMQ. The Short-chain Fatty Acid Propionic Acid Activates the Rcs Stress Response System Partially through Inhibition of d-Alanine Racemase. mSphere 2023; 8:e0043922. [PMID: 36645277 PMCID: PMC9942566 DOI: 10.1128/msphere.00439-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 12/16/2022] [Indexed: 01/17/2023] Open
Abstract
The Enterobacterial Rcs stress response system reacts to envelope stresses through a complex two-component phosphorelay system to regulate a variety of environmental response genes, such as capsular polysaccharide and flagella biosynthesis genes. However, beyond Escherichia coli, the stresses that activate Rcs are not well-understood. In this study, we used a Rcs system-dependent luminescent transcriptional reporter to screen a library of over 240 antimicrobial compounds for those that activated the Rcs system in Serratia marcescens, a Yersiniaceae family bacterium. Using an isogenic rcsB mutant to establish specificity, both new and expected activators were identified, including the short-chain fatty acid propionic acid, which is found at millimolar levels in the human gut. Propionic acid did not reduce the bacterial intracellular pH, as was hypothesized for its antibacterial mechanism. Instead, data suggest that the Rcs-activation by propionic acid is due, in part, to an inactivation of alanine racemase. This enzyme is responsible for the biosynthesis of d-alanine, which is an amino-acid that is required for the generation of bacterial cell walls. Consistent with what was observed in S. marcescens, in E. coli, alanine racemase mutants demonstrated elevated expression of the Rcs-reporter in a d-alanine-dependent and RcsB-dependent manner. These results suggest that host gut short-chain fatty acids can influence bacterial behavior via the activation of the Rcs stress response system. IMPORTANCE The Rcs bacterial stress response system responds to envelope stresses by globally altering gene expression to profoundly impact host-pathogen interactions, virulence, and antibiotic tolerance. In this study, a luminescent Rcs-reporter plasmid was used to screen a library of compounds for activators of Rcs. Among the strongest inducers was the short-chain fatty acid propionic acid, which is found at high concentrations in the human gut. This study suggests that gut short-chain fatty acids can affect both bacterial virulence and antibiotic tolerance via the induction of the Rcs system.
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Affiliation(s)
- Nathaniel S. Harshaw
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Mitchell D. Meyer
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Nicholas A. Stella
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Kara M. Lehner
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Regis P. Kowalski
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Robert M. Q. Shanks
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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3
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Lach SR, Kumar S, Kim S, Im W, Konovalova A. Conformational rearrangements in the sensory RcsF/OMP complex mediate signal transduction across the bacterial cell envelope. PLoS Genet 2023; 19:e1010601. [PMID: 36706155 PMCID: PMC9907809 DOI: 10.1371/journal.pgen.1010601] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2022] [Revised: 02/08/2023] [Accepted: 01/06/2023] [Indexed: 01/28/2023] Open
Abstract
Timely detection and repair of envelope damage are paramount for bacterial survival. The Regulator of Capsule Synthesis (Rcs) stress response can transduce the stress signals across the multilayered gram-negative cell envelope to regulate gene expression in the cytoplasm. Previous studies defined the overall pathway, which begins with the sensory lipoprotein RcsF interacting with several outer membrane proteins (OMPs). RcsF can also interact with the periplasmic domain of the negative regulator IgaA, derepressing the downstream RcsCDB phosphorelay. However, how the RcsF/IgaA interaction is regulated at the molecular level to activate the signaling in response to stress remains poorly understood. In this study, we used a site-saturated mutant library of rcsF to carry out several independent genetic screens to interrogate the mechanism of signal transduction from RcsF to IgaA. We analyzed several distinct classes of rcsF signaling mutants, and determined the region of RcsF that is critically important for signal transduction. This region is bifunctional as it is important for RcsF interaction with both IgaA and OMPs. The mutant analysis provides strong evidence for conformational changes in the RcsF/OMP complex mediating signal transduction to IgaA, and the first direct evidence that OMPs play an important regulatory role in Rcs signaling.
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Affiliation(s)
- Sarah R. Lach
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas, United States of America
| | - Santosh Kumar
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
| | - Seonghoon Kim
- Departments of Biological Sciences, Chemistry, Bioengineering, and Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States of America
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul, Republic of Korea
| | - Wonpil Im
- Departments of Biological Sciences, Chemistry, Bioengineering, and Computer Science and Engineering, Lehigh University, Bethlehem, Pennsylvania, United States of America
| | - Anna Konovalova
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), Houston, Texas, United States of America
- The University of Texas MD Anderson UTHealth Graduate School of Biomedical Sciences, Houston, Texas, United States of America
- * E-mail:
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Weerakoon D, Petrov K, Pedebos C, Khalid S. Polymyxin B1 within the E. coli cell envelope: insights from molecular dynamics simulations. Biophys Rev 2021; 13:1061-1070. [PMID: 35047090 PMCID: PMC8724489 DOI: 10.1007/s12551-021-00869-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 10/22/2021] [Indexed: 11/25/2022] Open
Abstract
Polymyxins are used as last-resort antibiotics, where other treatments have been ineffectual due to antibiotic resistance. However, resistance to polymyxins has also been now reported, therefore it is instructive to characterise at the molecular level, the mechanisms of action of polymyxins. Here we review insights into these mechanisms from molecular dynamics simulations and discuss the utility of simulations as a complementary technique to experimental methodologies.
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Affiliation(s)
| | - Kamen Petrov
- Hertford College, University of Oxford, Oxford, OX1 3BW UK
| | - Conrado Pedebos
- School of Chemistry, University of Southampton, Southampton, SO17 1BJ UK
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU UK
| | - Syma Khalid
- School of Chemistry, University of Southampton, Southampton, SO17 1BJ UK
- Department of Biochemistry, University of Oxford, Oxford, OX1 3QU UK
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5
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High-throughput suppressor screen demonstrates that RcsF monitors outer membrane integrity and not Bam complex function. Proc Natl Acad Sci U S A 2021; 118:2100369118. [PMID: 34349021 DOI: 10.1073/pnas.2100369118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The regulator of capsule synthesis (Rcs) is a complex signaling cascade that monitors gram-negative cell envelope integrity. The outer membrane (OM) lipoprotein RcsF is the sensory component, but how RcsF functions remains elusive. RcsF interacts with the β-barrel assembly machinery (Bam) complex, which assembles RcsF in complex with OM proteins (OMPs), resulting in RcsF's partial cell surface exposure. Elucidating whether RcsF/Bam or RcsF/OMP interactions are important for its sensing function is challenging because the Bam complex is essential, and partial loss-of-function mutations broadly compromise the OM biogenesis. Our recent discovery that, in the absence of nonessential component BamE, RcsF inhibits function of the central component BamA provided a genetic tool to select mutations that specifically prevent RcsF/BamA interactions. We employed a high-throughput suppressor screen to isolate a collection of such rcsF and bamA mutants and characterized their impact on RcsF/OMP assembly and Rcs signaling. Using these mutants and BamA inhibitors MRL-494L and darobactin, we provide multiple lines of evidence against the model in which RcsF senses Bam complex function. We show that Rcs activation in bam mutants results from secondary OM and lipopolysaccharide defects and that RcsF/OMP assembly is required for this activation, supporting an active role of RcsF/OMP complexes in sensing OM stress.
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Saha S, Lach SR, Konovalova A. Homeostasis of the Gram-negative cell envelope. Curr Opin Microbiol 2021; 61:99-106. [PMID: 33901778 DOI: 10.1016/j.mib.2021.03.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 01/08/2023]
Abstract
The Gram-negative bacterial cell envelope is a complex structure and its homeostasis is essential for bacterial survival. Envelope stress responses (ESRs) are signal transduction pathways that monitor the fidelity of envelope assembly during normal growth and also detect and repair envelope damage caused by external assaults, including immune factors, protein toxins, and antibiotics. In this review, we focus on three best-studied ESRs and discuss the mechanisms by which ESRs detect various perturbations of envelope assembly and integrity and regulate envelope remodeling to promote bacterial survival. We will highlight the complex relationship of ESRs with envelope biogenesis pathways and discuss some of the challenges in this field on the road to mapping the global regulatory network of envelope homeostasis.
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Affiliation(s)
- Shreya Saha
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Sarah R Lach
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA; MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, 6767 Bertner Avenue, Houston, TX, 77030, USA
| | - Anna Konovalova
- Department of Microbiology and Molecular Genetics, McGovern Medical School, The University of Texas Health Science Center at Houston (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA.
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Dowhan W, Bogdanov M. Eugene P. Kennedy's Legacy: Defining Bacterial Phospholipid Pathways and Function. Front Mol Biosci 2021; 8:666203. [PMID: 33842554 PMCID: PMC8027125 DOI: 10.3389/fmolb.2021.666203] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 03/01/2021] [Indexed: 12/27/2022] Open
Abstract
In the 1950's and 1960's Eugene P. Kennedy laid out the blueprint for phospholipid biosynthesis in somatic cells and Escherichia coli, which have been coined the Kennedy Pathways for phospholipid biosynthesis. His research group continued to make seminal contributions in the area of phospholipids until his retirement in the early 1990's. During these years he mentored many young scientists that continued to build on his early discoveries and who also mentored additional scientists that continue to make important contributions in areas related to phospholipids and membrane biogenesis. This review will focus on the initial E. coli Kennedy Pathways and how his early contributions have laid the foundation for our current understanding of bacterial phospholipid genetics, biochemistry and function as carried on by his scientific progeny and others who have been inspired to study microbial phospholipids.
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Affiliation(s)
- William Dowhan
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, United States
| | - Mikhail Bogdanov
- Department of Biochemistry and Molecular Biology, McGovern Medical School, University of Texas Health Science Center, Houston, TX, United States
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Meng J, Young G, Chen J. The Rcs System in Enterobacteriaceae: Envelope Stress Responses and Virulence Regulation. Front Microbiol 2021; 12:627104. [PMID: 33658986 PMCID: PMC7917084 DOI: 10.3389/fmicb.2021.627104] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 01/18/2021] [Indexed: 11/13/2022] Open
Abstract
The bacterial cell envelope is a protective barrier at the frontline of bacterial interaction with the environment, and its integrity is regulated by various stress response systems. The Rcs (regulator of capsule synthesis) system, a non-orthodox two-component regulatory system (TCS) found in many members of the Enterobacteriaceae family, is one of the envelope stress response pathways. The Rcs system can sense envelope damage or defects and regulate the transcriptome to counteract stress, which is particularly important for the survival and virulence of pathogenic bacteria. In this review, we summarize the roles of the Rcs system in envelope stress responses (ESRs) and virulence regulation. We discuss the environmental and intrinsic sources of envelope stress that cause activation of the Rcs system with an emphasis on the role of RcsF in detection of envelope stress and signal transduction. Finally, the different regulation mechanisms governing the Rcs system's control of virulence in several common pathogens are introduced. This review highlights the important role of the Rcs system in the environmental adaptation of bacteria and provides a theoretical basis for the development of new strategies for control, prevention, and treatment of bacterial infections.
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Affiliation(s)
- Jiao Meng
- Beijing Laboratory for Food Quality and Safety, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
| | - Glenn Young
- Department of Food Science and Technology, University of California, Davis, Davis, CA, United States
| | - Jingyu Chen
- Beijing Laboratory for Food Quality and Safety, College of Food Science and Nutritional Engineering, China Agricultural University, Beijing, China
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El Rayes J, Rodríguez-Alonso R, Collet JF. Lipoproteins in Gram-negative bacteria: new insights into their biogenesis, subcellular targeting and functional roles. Curr Opin Microbiol 2021; 61:25-34. [PMID: 33667939 DOI: 10.1016/j.mib.2021.02.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 02/05/2021] [Accepted: 02/08/2021] [Indexed: 02/06/2023]
Abstract
Bacterial lipoproteins are globular proteins anchored to a membrane by a lipid moiety. By discovering new functions carried out by lipoproteins, recent research has highlighted the crucial roles played by these proteins in the cell envelope of Gram-negative bacteria. Here, after discussing the wide range of activities carried out by lipoproteins in the model bacterium Escherichia coli, we review new insights into the essential mechanisms involved in lipoprotein maturation, sorting and targeting to their final destination. A special attention will also be given to the recent identification of lipoproteins on the surface of E. coli and of other bacteria. The renewed interest in lipoproteins is driven by the need to identify novel targets for antibiotic development.
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Affiliation(s)
- Jessica El Rayes
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Raquel Rodríguez-Alonso
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium
| | - Jean-François Collet
- WELBIO, Avenue Hippocrate 75, 1200 Brussels, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, 1200 Brussels, Belgium.
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10
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Pedebos C, Smith IPS, Boags A, Khalid S. The hitchhiker's guide to the periplasm: Unexpected molecular interactions of polymyxin B1 in E. coli. Structure 2021; 29:444-456.e2. [PMID: 33577754 DOI: 10.1016/j.str.2021.01.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 12/11/2020] [Accepted: 01/21/2021] [Indexed: 12/19/2022]
Abstract
The periplasm of Gram-negative bacteria is a complex, highly crowded molecular environment. Little is known about how antibiotics move across the periplasm and the interactions they experience. Here, atomistic molecular dynamics simulations are used to study the antibiotic polymyxin B1 within models of the periplasm, which are crowded to different extents. We show that PMB1 is likely to be able to "hitchhike" within the periplasm by binding to lipoprotein carriers-a previously unreported passive transport route. The simulations reveal that PMB1 forms both transient and long-lived interactions with proteins, osmolytes, lipids of the outer membrane, and the cell wall, and is rarely uncomplexed when in the periplasm. Furthermore, it can interfere in the conformational dynamics of native proteins. These are important considerations for interpreting its mechanism of action and are likely to also hold for other antibiotics that rely on diffusion to cross the periplasm.
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Affiliation(s)
- Conrado Pedebos
- School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK
| | - Iain Peter Shand Smith
- School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK
| | - Alister Boags
- School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK
| | - Syma Khalid
- School of Chemistry, University of Southampton, Highfield Campus, Southampton SO17 1BJ, UK.
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Feng Z, Liu D, Liu Z, Liang Y, Wang Y, Liu Q, Liu Z, Zang Z, Cui Y. Cloning and Functional Characterization of Putative Escherichia coli ABC Multidrug Efflux Transporter YddA. J Microbiol Biotechnol 2020; 30:982-995. [PMID: 32347079 PMCID: PMC9728188 DOI: 10.4014/jmb.2003.03003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 04/23/2020] [Indexed: 12/15/2022]
Abstract
A putative multidrug efflux gene, yddA, was cloned from the Escherichia coli K-12 strain. A drugsensitive strain of E. coli missing the main multidrug efflux pump AcrB was constructed as a host and the yddA gene was knocked out in wild-type (WT) and drug-sensitive E. coliΔacrB to study the yddA function. Sensitivity to different substrates of WT E.coli, E. coliΔyddA, E. coliΔacrB and E. coliΔacrBΔyddA strains was compared with minimal inhibitory concentration (MIC) assays and fluorescence tests. MIC assay and fluorescence test results showed that YddA protein was a multidrug efflux pump that exported multiple substrates. Three inhibitors, ortho-vanadate, carbonyl cyanide m-chlorophenylhydrazone (CCCP), and reserpine, were used in fluorescence tests. Ortho-vanadate and reserpine significantly inhibited the efflux and increased accumulation of ethidium bromide and norfloxacin, while CCCP had no significant effect on YddA-regulated efflux. The results indicated that YddA relies on energy released from ATP hydrolysis to transfer the substrates and YddA is an ABC-type multidrug exporter. Functional study of unknown ATP-binding cassette (ABC) superfamily transporters in the model organism E. coli is conducive to discovering new multidrug resistance-reversal targets and providing references for studying other ABC proteins of unknown function.
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Affiliation(s)
- Zhenyue Feng
- College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China,College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Defu Liu
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Ziwen Liu
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Yimin Liang
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Yanhong Wang
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Qingpeng Liu
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Zhenhua Liu
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Zhongjing Zang
- College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China
| | - Yudong Cui
- College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China,College of Life Science and Technology, Heilongjiang Bayi Agricultural University, Daqing 163319, P.R. China,Corresponding author Phone/Fax: +459-6031177 E-mail:
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Abstract
The Gram-negative envelope is a complex structure that consists of the inner membrane, the periplasm, peptidoglycan and the outer membrane, and protects the bacterial cell from the environment. Changing environmental conditions can cause damage, which triggers the envelope stress responses to maintain cellular homeostasis. In this Review, we explore the causes, both environmental and intrinsic, of envelope stress, as well as the cellular stress response pathways that counter these stresses. Furthermore, we discuss the damage to the cell that occurs when these pathways are aberrantly activated either in the absence of stress or to an excessive degree. Finally, we review the mechanisms whereby the σE response constantly acts to prevent cell death caused by highly toxic unfolded outer membrane proteins. Together, the recent work that we discuss has provided insights that emphasize the necessity for proper levels of stress response activation and the detrimental consequences that can occur in the absence of proper regulation.
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The Lipoprotein NlpE Is a Cpx Sensor That Serves as a Sentinel for Protein Sorting and Folding Defects in the Escherichia coli Envelope. J Bacteriol 2019; 201:JB.00611-18. [PMID: 30833359 DOI: 10.1128/jb.00611-18] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 03/01/2019] [Indexed: 12/18/2022] Open
Abstract
The envelope of Gram-negative bacteria is a complex compartment that is essential for viability. To ensure survival of the bacterial cells in fluctuating environments, several signal transduction systems, called envelope stress response systems (ESRSs), exist to monitor envelope biogenesis and homeostasis. The Cpx two-component system is an extensively studied ESRS in Escherichia coli that is active during exposure to a vast array of stresses and protects the envelope under those harmful circumstances. Overproduction of NlpE, a two-domain outer membrane lipoprotein of unclear function, has been used in numerous studies as a molecular trigger to turn on the system artificially. However, the mechanism of Cpx activation by NlpE, as well as its physiological relevance, awaited further investigation. In this paper, we provide novel insights into the role played by NlpE in the Cpx system. We found that, among all outer membrane lipoproteins in E. coli, NlpE is sufficient to induce Cpx when lipoprotein trafficking is perturbed. Under such conditions, fitness is increased by the presence of NlpE. Moreover, we show that NlpE, through its N-terminal domain, physically interacts with the Cpx sensor kinase CpxA. Our data suggest that NlpE also serves to activate the Cpx system during oxidative folding defects in the periplasm and that its C-terminal domain is involved in the sensing mechanism. Overall, our data demonstrate that NlpE acts as a sentinel for two important envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding, and they further establish NlpE as a bona fide member of the Cpx two-component system.IMPORTANCE Bacteria rely on a sophisticated envelope to shield them against challenging environmental conditions and therefore need to ensure correct envelope assembly and integrity. A major signaling pathway that performs this role in Gram-negative species is the Cpx system. An outer membrane lipoprotein of unclear function, NlpE, has long been exploited as a research tool to study Cpx in E. coli, since it triggers this system when overproduced or mislocalized; however, the mechanism and physiological relevance of the NlpE-Cpx connection have awaited further investigation. We elucidate a new function for NlpE by showing that it physically interacts with the Cpx sensor CpxA and acts as a sentinel that specifically monitors two essential envelope biogenesis processes, namely, lipoprotein sorting and oxidative folding.
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Hashemi MM, Holden BS, Coburn J, Taylor MF, Weber S, Hilton B, Zaugg AL, McEwan C, Carson R, Andersen JL, Price JC, Deng S, Savage PB. Proteomic Analysis of Resistance of Gram-Negative Bacteria to Chlorhexidine and Impacts on Susceptibility to Colistin, Antimicrobial Peptides, and Ceragenins. Front Microbiol 2019; 10:210. [PMID: 30833936 PMCID: PMC6388577 DOI: 10.3389/fmicb.2019.00210] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Accepted: 01/24/2019] [Indexed: 12/19/2022] Open
Abstract
Use of chlorhexidine in clinical settings has led to concerns that repeated exposure of bacteria to sub-lethal doses of chlorhexidine might result in chlorhexidine resistance and cross resistance with other cationic antimicrobials including colistin, endogenous antimicrobial peptides (AMPs) and their mimics, ceragenins. We have previously shown that colistin-resistant Gram-negative bacteria remain susceptible to AMPs and ceragenins. Here, we investigated the potential for cross resistance between chlorhexidine, colistin, AMPs and ceragenins by serial exposure of standard strains of Gram-negative bacteria to chlorhexidine to generate resistant populations of organisms. Furthermore, we performed a proteomics study on the chlorhexidine-resistant strains and compared them to the wild-type strains to find the pathways by which bacteria develop resistance to chlorhexidine. Serial exposure of Gram-negative bacteria to chlorhexidine resulted in four- to eight-fold increases in minimum inhibitory concentrations (MICs). Chlorhexidine-resistant organisms showed decreased susceptibility to colistin (8- to 32-fold increases in MICs) despite not being exposed to colistin. In contrast, chlorhexidine-resistant organisms had the same MICs as the original strains when tested with representative AMPs (LL-37 and magainin I) and ceragenins (CSA-44 and CSA-131). These results imply that there may be a connection between the emergence of highly colistin-resistant Gram-negative pathogens and the prevalence of chlorhexidine usage. Yet, use of chlorhexidine may not impact innate immune defenses (e.g., AMPs) and their mimics (e.g., ceragenins). Here, we also show that chlorhexidine resistance is associated with upregulation of proteins involved in the assembly of LPS for outer membrane biogenesis and virulence factors in Pseudomonas aeruginosa. Additionally, resistance to chlorhexidine resulted in elevated expression levels of proteins associated with chaperones, efflux pumps, flagella and cell metabolism. This study provides a comprehensive overview of the evolutionary proteomic changes in P. aeruginosa following exposure to chlorhexidine and colistin. These results have important clinical implications considering the continuous application of chlorhexidine in hospitals that could influence the emergence of colistin-resistant strains.
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Affiliation(s)
- Marjan M Hashemi
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Brett S Holden
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Jordan Coburn
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Maddison F Taylor
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Scott Weber
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Brian Hilton
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Aaron L Zaugg
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Colten McEwan
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Richard Carson
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Joshua L Andersen
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - John C Price
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Shenglou Deng
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
| | - Paul B Savage
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, United States
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15
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Liao CT, Chiang YC, Hsiao YM. Functional characterization and proteomic analysis of lolA in Xanthomonas campestris pv. campestris. BMC Microbiol 2019; 19:20. [PMID: 30665348 PMCID: PMC6341742 DOI: 10.1186/s12866-019-1387-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Accepted: 01/02/2019] [Indexed: 12/31/2022] Open
Abstract
Background The gram-negative Xanthomonas campestris pv. campestris is the pathogenic bacterium that causes black rot disease in crucifers. The virulence determinants of this bacterium include extracellular enzymes, exopolysaccharides, and biofilm formation. Here, one transposon mutant of X. campestris pv. campestris strain 17 that affects biofilm formation was isolated, and subsequent analyses led to the identification of the lolA gene, which encodes an outer membrane lipoprotein chaperone. Results The lolA mutant exhibited significant reductions in bacterial attachment, extracellular enzyme production, virulence, and tolerance in the presence of myriad membrane-perturbing agents. These phenotypic changes of the mutant could be complemented to the wild-type level through the intact lolA gene. Proteomic analysis revealed that 109 proteins were differentially expressed after lolA mutation. These differentially expressed proteins were categorized in various functional groups and were mainly associated with the membrane component, were involved in transport, and contained receptor activity. Through reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) analysis, deletion of lolA was determined to have caused significantly reduced expression of genes that encode the major extracellular enzymes, the biofilm-related proteins, and the virulence-related proteins. The RT-qPCR analysis also indicated that the expression of several genes that encode putative outer membrane lipoproteins and TonB-dependent receptors was reduced after lolA mutation. Conclusions This is the first report to define the lolA gene as a virulence factor and to contribute to the functional understanding of, and provide new information concerning, the role of lolA in Xanthomonas. Furthermore, the results of this study provide and extend new insights into the function of lolA in bacteria. Electronic supplementary material The online version of this article (10.1186/s12866-019-1387-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Chao-Tsai Liao
- Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan
| | - Ying-Chuan Chiang
- Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan
| | - Yi-Min Hsiao
- Department of Medical Laboratory Science and Biotechnology, Central Taiwan University of Science and Technology, Taichung, Taiwan.
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16
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Abstract
The Lpp lipoprotein of Escherichia coli is the first identified protein with a covalently linked lipid. It is chemically bound by its C-terminus to murein (peptidoglycan) and inserts by the lipid at the N-terminus into the outer membrane. As the most abundant protein in E. coli (106 molecules per cell) it plays an important role for the integrity of the cell envelope. Lpp represents the type protein of a large variety of lipoproteins found in Gram-negative and Gram-positive bacteria and in archaea that have in common the lipid structure for anchoring the proteins to membranes but otherwise strongly vary in sequence, structure, and function. Predicted lipoproteins in known prokaryotic genomes comprise 2.7% of all proteins. Lipoproteins are modified by a unique phospholipid pathway and transferred from the cytoplasmic membrane into the outer membrane by a special system. They are involved in protein incorporation into the outer membrane, protein secretion across the cytoplasmic membrane, periplasm and outer membrane, signal transduction, conjugation, cell wall metabolism, antibiotic resistance, biofilm formation, and adhesion to host tissues. They are only found in bacteria and function as signal molecules for the innate immune system of vertebrates, where they cause inflammation and elicit innate and adaptive immune response through Toll-like receptors. This review discusses various aspects of Lpp and other lipoproteins of Gram-negative and Gram-positive bacteria and archaea.
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Affiliation(s)
- Volkmar Braun
- Department of Protein Evolution, Max Planck Institute for Developmental Biology, Max Planck Ring 5, 72076, Tübingen, Germany.
| | - Klaus Hantke
- IMIT, University of Tuebingen, Auf der Morgenstelle 28, 72076, Tübingen, Germany
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17
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Gwin CM, Prakash N, Christian Belisario J, Haider L, Rosen ML, Martinez LR, Rigel NW. The apolipoprotein N-acyl transferase Lnt is dispensable for growth in Acinetobacter species. MICROBIOLOGY-SGM 2018; 164:1547-1556. [PMID: 30307391 DOI: 10.1099/mic.0.000726] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Directing the flow of protein traffic is a critical task faced by all cellular organisms. In Gram-negative bacteria, this traffic includes lipoproteins. Lipoproteins are synthesized as precursors in the cytoplasm and receive their acyl modifications upon export across the inner membrane. The third and final acyl chain is added by Lnt, which until recently was thought to be essential in all Gram-negatives. In this report, we show that Acinetobacter species can also tolerate a complete loss-of-function mutation in lnt. Absence of a fully functional Lnt impairs modification of lipoproteins, increases outer membrane permeability and susceptibility to antibiotics, and alters normal cellular morphology. In addition, we show that loss of lnt triggers a global transcriptional response to this added cellular stress. Taken together, our findings provide new insights on and support the growing revisions to the Gram-negative lipoprotein biogenesis paradigm.
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Affiliation(s)
- Celena M Gwin
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,2Department of Microbial Pathogenesis, Yale University, New Haven, CT, USA
| | - Natalia Prakash
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - J Christian Belisario
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA
| | - Lubaina Haider
- 1Department of Biology, Hofstra University, Hempstead, NY, USA.,4College of Medicine, SUNY-Downstate Medical Center, Brooklyn, NY, USA
| | - Marlene L Rosen
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
| | - Luis R Martinez
- 3Department of Biomedical Sciences, College of Osteopathic Medicine, New York Institute of Technology, Old Westbury, NY, USA.,5Department of Biological Sciences, The Border Biomedical Research Center, University of Texas at El Paso, El Paso, TX, USA
| | - Nathan W Rigel
- 1Department of Biology, Hofstra University, Hempstead, NY, USA
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18
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Abstract
RcsB, a response regulator of the FixJ/NarL family, is at the center of a complex network of regulatory inputs and outputs. Cell surface stress is sensed by an outer membrane lipoprotein, RcsF, which regulates interactions of the inner membrane protein IgaA, lifting negative regulation of a phosphorelay. In vivo evidence supports a pathway in which histidine kinase RcsC transfers phosphate to phosphotransfer protein RcsD, resulting in phosphorylation of RcsB. RcsB acts either alone or in combination with RcsA to positively regulate capsule synthesis and synthesis of small RNA (sRNA) RprA as well as other genes, and to negatively regulate motility. RcsB in combination with other FixJ/NarL auxiliary proteins regulates yet other functions, independent of RcsB phosphorylation. Proper expression of Rcs and its targets is critical for success of Escherichia coli commensal strains, for proper development of biofilm, and for virulence in some pathogens. New understanding of how the Rcs phosphorelay works provides insight into the flexibility of the two-component system paradigm.
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Affiliation(s)
- Erin Wall
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Nadim Majdalani
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
| | - Susan Gottesman
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland 20892, USA; emails: , ,
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19
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Hussein NA, Cho SH, Laloux G, Siam R, Collet JF. Distinct domains of Escherichia coli IgaA connect envelope stress sensing and down-regulation of the Rcs phosphorelay across subcellular compartments. PLoS Genet 2018; 14:e1007398. [PMID: 29852010 PMCID: PMC5978795 DOI: 10.1371/journal.pgen.1007398] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Accepted: 05/08/2018] [Indexed: 12/14/2022] Open
Abstract
In enterobacteria, the Rcs system (Regulator of capsule synthesis) monitors envelope integrity and induces a stress response when damages occur in the outer membrane or in the peptidoglycan layer. Built around a two-component system, Rcs controls gene expression via a cascade of phosphoryl transfer reactions. Being particularly complex, Rcs also involves the outer membrane lipoprotein RcsF and the inner membrane essential protein IgaA (Intracellular growth attenuator). RcsF and IgaA, which are located upstream of the phosphorelay, are required for normal Rcs functioning. Here, we establish the stress-dependent formation of a complex between RcsF and the periplasmic domain of IgaA as the molecular signal triggering Rcs. Moreover, molecular dissection of IgaA reveals that its negative regulatory role on Rcs is mostly carried by its first N-terminal cytoplasmic domain. Altogether, our results support a model in which IgaA regulates Rcs activation by playing a direct role in the transfer of signals from the cell envelope to the cytoplasm. This remarkable feature further distinguishes Rcs from other envelope stress response systems. A thorough understanding of the mechanisms that allow bacteria to thrive in various environments is crucial to the development of new antibiotics, an urgent endeavor to combat antimicrobial resistance. A landmark feature of Gram-negative bacteria is the presence of a multi-layered envelope. Because this structure is essential, its integrity is constantly monitored to detect and respond to potential breaches in a fast and adequate manner. Here, we describe how IgaA, an essential protein present in the cytoplasmic membrane of enterobacteria, participates in the transfer of stress signals from the envelope to the cytoplasm. We provide evidence that IgaA works in concert with RcsF, a lipoprotein that is posted as a sentinel in the outermost envelope layer, to detect envelope stress: under stress conditions, RcsF forms a complex with the C-terminal, periplasmic domain of IgaA. As a result, cells turn on the Rcs response. We also discovered that the N-terminal, cytoplasmic domain of IgaA plays an important role in inhibiting Rcs in the absence of stress. Together, these findings reveal that distinct IgaA domains coordinate stress sensing and Rcs activation across the cytoplasmic membrane. They enhance our understanding of Rcs regulation and open new avenues for the development of new antibacterials.
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Affiliation(s)
- Nahla A. Hussein
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- Biology Department, Biotechnology Graduate Program and YJ-Science and Technology Research Center, American University in Cairo, Cairo, Egypt
| | - Seung-Hyun Cho
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Géraldine Laloux
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
| | - Rania Siam
- Biology Department, Biotechnology Graduate Program and YJ-Science and Technology Research Center, American University in Cairo, Cairo, Egypt
| | - Jean-François Collet
- WELBIO, Brussels, Belgium
- de Duve Institute, Université catholique de Louvain, Brussels, Belgium
- * E-mail:
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20
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Affiliation(s)
- Marcin Grabowicz
- Department of Microbiology and Immunology; Emory University School of Medicine; Atlanta GA 30322 USA
- Division of Infectious Disease; Department of Medicine; Emory University School of Medicine; Atlanta GA 30322 USA
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21
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Guo XP, Sun YC. New Insights into the Non-orthodox Two Component Rcs Phosphorelay System. Front Microbiol 2017; 8:2014. [PMID: 29089936 PMCID: PMC5651002 DOI: 10.3389/fmicb.2017.02014] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 09/29/2017] [Indexed: 01/18/2023] Open
Abstract
The Rcs phosphorelay system, a non-orthodox two-component regulatory system, integrates environmental signals, regulates gene expression, and alters the physiological behavior of members of the Enterobacteriaceae family of Gram-negative bacteria. Recent studies of Rcs system focused on protein interactions, functions, and the evolution of Rcs system components and its auxiliary regulatory proteins. Herein we review the latest advances on the Rcs system proteins, and discuss the roles that the Rcs system plays in the environmental adaptation of various Enterobacteriaceae species.
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Affiliation(s)
- Xiao-Peng Guo
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yi-Cheng Sun
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
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22
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Major Tom to Ground Control: How Lipoproteins Communicate Extracytoplasmic Stress to the Decision Center of the Cell. J Bacteriol 2017; 199:JB.00216-17. [PMID: 28674071 DOI: 10.1128/jb.00216-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The envelope of bacteria is a complex multilayered shield that ensures multiple essential functions, including protecting the cell from external assaults. Hence, bacterial cells have evolved intricate mechanisms called envelope stress response systems (ESRS) to monitor all kinds of perturbations affecting the integrity of their envelope and to mount an appropriate response to contain or repair the damage. In the model bacterium Escherichia coli, several ESRS are built around a two-component system, in which envelope stress triggers a phosphotransfer between a sensor protein in the inner membrane of the envelope and a response regulator in the cytoplasm. In this review, we focus on two major ESRS in E. coli, the Rcs and Cpx pathways, in which additional proteins not directly involved in the phosphotransfer modulate signal transduction. Both the Rcs and Cpx systems can be turned on by a lipoprotein anchored in the outer membrane, RcsF and NlpE, respectively, providing a molecular connection between the most exterior layer of the envelope and the ground control center in the cytoplasm. Here, we review how these two lipoproteins, which share a striking set of features while being distinct in several aspects, act as sentinels at the front line of the bacterium by sensing and transducing stress to the downstream components of the Rcs and Cpx systems.
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23
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Narita SI, Tokuda H. Bacterial lipoproteins; biogenesis, sorting and quality control. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1862:1414-1423. [PMID: 27871940 DOI: 10.1016/j.bbalip.2016.11.009] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2016] [Revised: 11/11/2016] [Accepted: 11/14/2016] [Indexed: 12/20/2022]
Abstract
Bacterial lipoproteins are a subset of membrane proteins localized on either leaflet of the lipid bilayer. These proteins are anchored to membranes through their N-terminal lipid moiety attached to a conserved Cys. Since the protein moiety of most lipoproteins is hydrophilic, they are expected to play various roles in a hydrophilic environment outside the cytoplasmic membrane. Gram-negative bacteria such as Escherichia coli possess an outer membrane, to which most lipoproteins are sorted. The Lol pathway plays a central role in the sorting of lipoproteins to the outer membrane after lipoprotein precursors are processed to mature forms in the cytoplasmic membrane. Most lipoproteins are anchored to the inner leaflet of the outer membrane with their protein moiety in the periplasm. However, recent studies indicated that some lipoproteins further undergo topology change in the outer membrane, and play critical roles in the biogenesis and quality control of the outer membrane. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Affiliation(s)
| | - Hajime Tokuda
- University of Morioka, Takizawa, Iwate 020-0694, Japan.
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24
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A penicillin-binding protein inhibits selection of colistin-resistant, lipooligosaccharide-deficient Acinetobacter baumannii. Proc Natl Acad Sci U S A 2016; 113:E6228-E6237. [PMID: 27681618 DOI: 10.1073/pnas.1611594113] [Citation(s) in RCA: 97] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
The Gram-negative bacterial outer membrane fortifies the cell against environmental toxins including antibiotics. Unique glycolipids called lipopolysaccharide/lipooligosaccharide (LPS/LOS) are enriched in the cell-surface monolayer of the outer membrane and promote antimicrobial resistance. Colistin, which targets the lipid A domain of LPS/LOS to lyse the cell, is the last-line treatment for multidrug-resistant Gram-negative infections. Lipid A is essential for the survival of most Gram-negative bacteria, but colistin-resistant Acinetobacter baumannii lacking lipid A were isolated after colistin exposure. Previously, strain ATCC 19606 was the only A. baumannii strain demonstrated to subsist without lipid A. Here, we show that other A. baumannii strains can also survive without lipid A, but some cannot, affording a unique model to study endotoxin essentiality. We assessed the capacity of 15 clinical A. baumannii isolates including 9 recent clinical isolates to develop colistin resistance through inactivation of the lipid A biosynthetic pathway, the products of which assemble the LOS precursor. Our investigation determined that expression of the well-conserved penicillin-binding protein (PBP) 1A, prevented LOS-deficient colony isolation. The glycosyltransferase activity of PBP1A, which aids in the polymerization of the peptidoglycan cell wall, was lethal to LOS-deficient A. baumannii Global transcriptomic analysis of a PBP1A-deficient mutant and four LOS-deficient A. baumannii strains showed a concomitant increase in transcription of lipoproteins and their transporters. Examination of the LOS-deficient A. baumannii cell surface demonstrated that specific lipoproteins were overexpressed and decorated the cell surface, potentially compensating for LOS removal. This work expands our knowledge of lipid A essentiality and elucidates a drug resistance mechanism.
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25
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Klein G, Stupak A, Biernacka D, Wojtkiewicz P, Lindner B, Raina S. Multiple Transcriptional Factors Regulate Transcription of the rpoE Gene in Escherichia coli under Different Growth Conditions and When the Lipopolysaccharide Biosynthesis Is Defective. J Biol Chem 2016; 291:22999-23019. [PMID: 27629414 DOI: 10.1074/jbc.m116.748954] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Indexed: 12/22/2022] Open
Abstract
The RpoE σ factor is essential for the viability of Escherichia coli RpoE regulates extracytoplasmic functions including lipopolysaccharide (LPS) translocation and some of its non-stoichiometric modifications. Transcription of the rpoE gene is positively autoregulated by EσE and by unknown mechanisms that control the expression of its distally located promoter(s). Mapping of 5' ends of rpoE mRNA identified five new transcriptional initiation sites (P1 to P5) located distal to EσE-regulated promoter. These promoters are activated in response to unique signals. Of these P2, P3, and P4 defined major promoters, recognized by RpoN, RpoD, and RpoS σ factors, respectively. Isolation of trans-acting factors, in vitro transcriptional and gel retardation assays revealed that the RpoN-recognized P2 promoter is positively regulated by a QseE/F two-component system and NtrC activator, whereas the RpoD-regulated P3 promoter is positively regulated by a Rcs system in response to defects in LPS core biosynthesis, overproduction of certain lipoproteins, and the global regulator CRP. Strains synthesizing Kdo2-LA LPS caused up to 7-fold increase in the rpoEP3 activity, which was abrogated in Δ(waaC rcsB). Overexpression of a novel 73-nucleotide sRNA rirA (RfaH interacting RNA) generated by the processing of 5' UTR of the waaQ mRNA induces the rpoEP3 promoter activity concomitant with a decrease in LPS content and defects in the O-antigen incorporation. In the presence of RNA polymerase, RirA binds LPS regulator RfaH known to prevent premature transcriptional termination of waaQ and rfb operons. RirA in excess could titrate out RfaH causing LPS defects and the activation of rpoE transcription.
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Affiliation(s)
- Gracjana Klein
- From the Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland and
| | - Anna Stupak
- From the Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland and
| | - Daria Biernacka
- From the Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland and
| | - Pawel Wojtkiewicz
- From the Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland and
| | - Buko Lindner
- the Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany
| | - Satish Raina
- From the Unit of Bacterial Genetics, Gdansk University of Technology, Narutowicza 11/12, 80-233, Gdansk, Poland and
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26
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Konovalova A, Mitchell AM, Silhavy TJ. A lipoprotein/β-barrel complex monitors lipopolysaccharide integrity transducing information across the outer membrane. eLife 2016; 5. [PMID: 27282389 PMCID: PMC4942254 DOI: 10.7554/elife.15276] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 06/07/2016] [Indexed: 11/13/2022] Open
Abstract
Lipoprotein RcsF is the OM component of the Rcs envelope stress response. RcsF exists in complexes with β-barrel proteins (OMPs) allowing it to adopt a transmembrane orientation with a lipidated N-terminal domain on the cell surface and a periplasmic C-terminal domain. Here we report that mutations that remove BamE or alter a residue in the RcsF trans-lumen domain specifically prevent assembly of the interlocked complexes without inactivating either RcsF or the OMP. Using these mutations we demonstrate that these RcsF/OMP complexes are required for sensing OM outer leaflet stress. Using mutations that alter the positively charged surface-exposed domain, we show that RcsF monitors lateral interactions between lipopolysaccharide (LPS) molecules. When these interactions are disrupted by cationic antimicrobial peptides, or by the loss of negatively charged phosphate groups on the LPS molecule, this information is transduced to the RcsF C-terminal signaling domain located in the periplasm to activate the stress response. DOI:http://dx.doi.org/10.7554/eLife.15276.001 Many disease-causing bacteria have an outer membrane that surrounds and protects the cell, while many hosts of these bacteria produce molecules called antimicrobial peptides that disrupt this outer membrane. In response to this attack, bacteria have evolved a defense system to reinforce their membrane when antimicrobial peptides are present. However, it was not clear how the bacteria sensed these peptides. One clue came from a recent discovery that the bacterial protein required for sensing the peptides is threaded through a barrel-shaped protein to expose a section of it on the bacterial cell’s surface. Now, Konovalova et al. have tested if this surface-exposed domain directly detects damage to the outer membrane caused by the antimicrobial peptides. The investigation revealed several mutants of Escherichia coli that still make the sensor protein but are unable to thread it through the barrel-shaped protein and place a portion on the cell surface. Konovalova et al. showed that these mutants are essentially “blind” to the presence of antimicrobial peptides, and thus prove that it is the surface-exposed domain that works as the sensor. Antimicrobial peptides bind to a major component of the outer membrane and disrupt its normal interactions. Further experiments showed that positively charged sites in surface-exposed domain of the sensor are required to detect these changes and transmit this information inside the cell. Future studies are now needed to understand how the sensor is assembled inside the barrel-shaped protein, and how the danger signal is sent across the membranes that envelope bacterial cells to activate the defense system inside the cell. DOI:http://dx.doi.org/10.7554/eLife.15276.002
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
| | - Angela M Mitchell
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
| | - Thomas J Silhavy
- Department of Molecular Biology, Princeton University, Lewis Thomas Laboratory, Princeton, United States
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27
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Cho SH, Szewczyk J, Pesavento C, Zietek M, Banzhaf M, Roszczenko P, Asmar A, Laloux G, Hov AK, Leverrier P, Van der Henst C, Vertommen D, Typas A, Collet JF. Detecting envelope stress by monitoring β-barrel assembly. Cell 2015; 159:1652-64. [PMID: 25525882 DOI: 10.1016/j.cell.2014.11.045] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 10/06/2014] [Accepted: 11/24/2014] [Indexed: 01/29/2023]
Abstract
The cell envelope protects bacteria from their surroundings. Defects in its integrity or assembly are sensed by signal transduction systems, allowing cells to rapidly adjust. The Rcs phosphorelay responds to outer membrane (OM)- and peptidoglycan-related stress in enterobacteria. We elucidated how the OM lipoprotein RcsF, the upstream Rcs component, senses envelope stress and activates the signaling cascade. RcsF interacts with BamA, the major component of the β-barrel assembly machinery. In growing cells, BamA continuously funnels RcsF through the β-barrel OmpA, displaying RcsF on the cell surface. This process spatially separates RcsF from the downstream Rcs component, which we show is the inner membrane protein IgaA. The Rcs system is activated when BamA fails to bind RcsF and funnel it to OmpA. Newly synthesized RcsF then remains periplasmic, interacting with IgaA to activate the cascade. Thus RcsF senses envelope damage by monitoring the activity of the Bam machinery.
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Affiliation(s)
- Seung-Hyun Cho
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Joanna Szewczyk
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Christina Pesavento
- European Molecular Biology Laboratory, Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Matylda Zietek
- European Molecular Biology Laboratory, Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Manuel Banzhaf
- European Molecular Biology Laboratory, Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Paula Roszczenko
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Abir Asmar
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Géraldine Laloux
- de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Ann-Kristin Hov
- European Molecular Biology Laboratory, Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Pauline Leverrier
- de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Charles Van der Henst
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Didier Vertommen
- de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium
| | - Athanasios Typas
- European Molecular Biology Laboratory, Genome Biology Unit, Meyerhofstrasse 1, 69117 Heidelberg, Germany.
| | - Jean-François Collet
- WELBIO, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium; de Duve Institute, Université catholique de Louvain, Avenue Hippocrate 75, Brussels 1200, Belgium.
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Morgan JK, Ortiz JA, Riordan JT. The role for TolA in enterohemorrhagic Escherichia coli pathogenesis and virulence gene transcription. Microb Pathog 2014; 77:42-52. [DOI: 10.1016/j.micpath.2014.10.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Revised: 10/14/2014] [Accepted: 10/21/2014] [Indexed: 01/16/2023]
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