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Aoyagi KL, Mathew B, Fisher MA. Enterobacterial common antigen biosynthesis in Yersinia pestis is tied to antimicrobial peptide resistance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.26.554945. [PMID: 37662240 PMCID: PMC10473683 DOI: 10.1101/2023.08.26.554945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Resistance to antimicrobial peptides (AMPs) plays an important role in allowing Yersinia pestis to maintain a successful infection in the flea vector Xenopsylla cheopis . Mutants that are unable to modify lipid A in their outer membrane with aminoarabinose (Ara4N), showed increased sensitivity to AMPs such as polymyxin B (PB), as well as decreased survival in fleas. A deletion mutant of wecE , a gene involved in biosynthesis of enterobacterial common antigen (ECA), also displayed hypersusceptibility to PB in vitro. Additional mutants in the ECA biosynthetic pathway were generated, some designed to cause accumulation of intermediate products that sequester undecaprenyl phosphate (Und-P), a lipid carrier that is also used in numerous other pathways, including for peptidoglycan, O-antigen, and Ara4N biosynthesis. Mutants that accumulate Und-PP-linked intermediates (ECA-lipid II) showed increased susceptibility to PB, reduced Ara4N-modified lipid A, altered cell morphology, and decreased ability to maintain flea infections. These effects are consistent with a model where Y. pestis has a sufficiently limited free Und-P pool such that sequestration of Und-P as ECA-lipid II prevents adequate Ara4N biosynthesis, ultimately resulting in AMP hypersusceptibility.
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2
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Trouillon J, Attrée I, Elsen S. The regulation of bacterial two-partner secretion systems. Mol Microbiol 2023; 120:159-177. [PMID: 37340956 DOI: 10.1111/mmi.15112] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2022] [Revised: 06/01/2023] [Accepted: 06/07/2023] [Indexed: 06/22/2023]
Abstract
Two-partner secretion (TPS) systems, also known as Type Vb secretion systems, allow the translocation of effector proteins across the outer membrane of Gram-negative bacteria. By secreting different classes of effectors, including cytolysins and adhesins, TPS systems play important roles in bacterial pathogenesis and host interactions. Here, we review the current knowledge on TPS systems regulation and highlight specific and common regulatory mechanisms across TPS functional classes. We discuss in detail the specific regulatory networks identified in various bacterial species and emphasize the importance of understanding the context-dependent regulation of TPS systems. Several regulatory cues reflecting host environment during infection, such as temperature and iron availability, are common determinants of expression for TPS systems, even across relatively distant species. These common regulatory pathways often affect TPS systems across subfamilies with different effector functions, representing conserved global infection-related regulatory mechanisms.
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Affiliation(s)
- Julian Trouillon
- Université Grenoble Alpes, CNRS, CEA, IBS UMR 5075, Team Bacterial Pathogenesis and Cellular Responses, Grenoble, France
| | - Ina Attrée
- Université Grenoble Alpes, CNRS, CEA, IBS UMR 5075, Team Bacterial Pathogenesis and Cellular Responses, Grenoble, France
| | - Sylvie Elsen
- Université Grenoble Alpes, CNRS, CEA, IBS UMR 5075, Team Bacterial Pathogenesis and Cellular Responses, Grenoble, France
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3
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Öztürk FY, Darcan C, Kariptaş E. The Determination, Monitoring, Molecular Mechanisms and Formation of Biofilm in E. coli. Braz J Microbiol 2023; 54:259-277. [PMID: 36577889 PMCID: PMC9943865 DOI: 10.1007/s42770-022-00895-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2022] [Accepted: 12/16/2022] [Indexed: 12/30/2022] Open
Abstract
Biofilms are cell assemblies embedded in an exopolysaccharide matrix formed by microorganisms of a single or many different species. This matrix in which they are embedded protects the bacteria from external influences and antimicrobial effects. The biofilm structure that microorganisms form to protect themselves from harsh environmental conditions and survive is found in nature in many different environments. These environments where biofilm formation occurs have in common that they are in contact with fluids. The gene expression of bacteria in complex biofilm differs from that of bacteria in the planktonic state. The differences in biofilm cell expression are one of the effects of community life. Means of quorum sensing, bacteria can act in coordination with each other. At the same time, while biofilm formation provides many benefits to bacteria, it has positive and negative effects in many different areas. Depending on where they occur, biofilms can cause serious health problems, contamination risks, corrosion, and heat and efficiency losses. However, they can also be used in water treatment plants, bioremediation, and energy production with microbial fuel cells. In this review, the basic steps of biofilm formation and biofilm regulation in the model organism Escherichia coli were discussed. Finally, the methods by which biofilm formation can be detected and monitored were briefly discussed.
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Affiliation(s)
- Fırat Yavuz Öztürk
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey.
| | - Cihan Darcan
- Department of Molecular Biology and Genetic, Faculty of Arts and Science, Bilecik Seyh Edebali University, Bilecik, Turkey
| | - Ergin Kariptaş
- Department of Medical Microbiology, Faculty of Medicine, Samsun University, Samsun, Turkey
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4
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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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5
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Phosphatidylglycerol Is the Lipid Donor for Synthesis of Phospholipid-Linked Enterobacterial Common Antigen. J Bacteriol 2023; 205:e0040322. [PMID: 36622229 PMCID: PMC9879101 DOI: 10.1128/jb.00403-22] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The Gram-negative outer membrane (OM) is an asymmetric bilayer with phospholipids in its inner leaflet and mainly lipopolysaccharide (LPS) in its outer leaflet and is largely impermeable to many antibiotics. In Enterobacterales (e.g., Escherichia, Salmonella, Klebsiella, and Yersinia), the outer leaflet of the OM also contains phosphoglyceride-linked enterobacterial common antigen (ECAPG). This molecule consists of the conserved ECA carbohydrate linked to diacylglycerol-phosphate (DAG-P) through a phosphodiester bond. ECAPG contributes to the OM permeability barrier and modeling suggests that it may alter the packing of LPS molecules in the OM. Here, we investigate, in Escherichia coli K-12, the reaction synthesizing ECAPG from ECA precursor linked to an isoprenoid carrier to identify the lipid donor that provides the DAG-P moiety to ECAPG. Through overexpression of phospholipid biosynthesis genes, we observed alterations expected to increase levels of phosphatidylglycerol (PG) increased the synthesis of ECAPG, whereas alterations expected to decrease levels of PG decreased the synthesis of ECAPG. We discovered depletion of PG levels in strains that could synthesize ECAPG, but not other forms of ECA, causes additional growth defects, likely due to the buildup of ECA precursor on the isoprenoid carrier inhibiting peptidoglycan biosynthesis. Our results demonstrate ECAPG can be synthesized in the absence of the other major phospholipids (phosphatidylethanolamine and cardiolipin). Overall, these results conclusively demonstrate PG is the lipid donor for the synthesis of ECAPG and provide a key insight into the reaction producing ECAPG. In addition, these results provide an interesting parallel to lipoprotein acylation, which also uses PG as its DAG donor. IMPORTANCE The Gram-negative outer membrane is a permeability barrier preventing cellular entry of antibiotics. However, outer membrane biogenesis pathways are targets for small molecule development. Here, we investigate the synthesis of a form of enterobacterial common antigen (ECA), ECAPG, found in the outer membrane of Enterobacterales (e.g., Escherichia, Salmonella, and Klebsiella). ECAPG consists of the conserved ECA carbohydrate unit linked to diacylglycerol-phosphate-ECA is a phospholipid headgroup. The details of the reaction forming this molecule from polymerized ECA precursor are unknown. We determined the lipid donor providing the phospholipid moiety is phosphatidylglycerol. Understanding the synthesis of outer membrane constituents such as ECAPG provides the opportunity for development of molecules to increase outer membrane permeability, expanding the antibiotics available to treat Gram-negative infections.
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Stella NA, Romanowski EG, Brothers KM, Calvario RC, Shanks RMQ. IgaA Protein, GumB, Has a Global Impact on the Transcriptome and Surface Proteome of Serratia marcescens. Infect Immun 2022; 90:e0039922. [PMID: 36317876 PMCID: PMC9671016 DOI: 10.1128/iai.00399-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 09/30/2022] [Indexed: 11/07/2022] Open
Abstract
Bacterial stress response signaling systems, like the Rcs system are triggered by membrane and cell wall damaging compounds, including antibiotics and immune system factors. These regulatory systems help bacteria survive envelope stress by altering the transcriptome resulting in protective phenotypic changes that may also influence the virulence of the bacterium. This study investigated the role of the Rcs stress response system using a clinical keratitis isolate of Serratia marcescens with a mutation in the gumB gene. GumB, an IgaA ortholog, inhibits activation of the Rcs system, such that mutants have overactive Rcs signaling. Transcriptomic analysis indicated that approximately 15% of all S. marcescens genes were significantly altered with 2-fold or greater changes in expression in the ΔgumB mutant compared to the wild type, indicating a global transcriptional regulatory role for GumB. We further investigated the phenotypic consequences of two classes of genes with altered expression in the ΔgumB mutant expected to contribute to infections: serralysin metalloproteases PrtS, SlpB, and SlpE, and type I pili coded by fimABCD. Secreted fractions from the ΔgumB mutant had reduced cytotoxicity to a corneal cell line, and could be complemented by induced expression of prtS, but not cytolysin shlBA, phospholipase phlAB, or flagellar master regulator flhDC operons. Proteomic analysis, qRT-PCR, and type I pili-dependent yeast agglutination indicated an inhibitory role for the Rcs system in adhesin production. Together these data demonstrate GumB has a global impact on S. marcescens gene expression that had measurable effects on bacterial cytotoxicity and surface adhesin production.
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Affiliation(s)
- Nicholas A. Stella
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania, USA
| | - Eric G. Romanowski
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania, USA
| | - Kimberly M. Brothers
- Department of Ophthalmology, University of Pittsburgh School of Medicine, Pittsburgh Pennsylvania, USA
| | - Rachel C. Calvario
- 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
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7
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Maczuga N, Tran ENH, Morona R. Subcellular localization of the enterobacterial common antigen GT-E-like glycosyltransferase, WecG. Mol Microbiol 2022; 118:403-416. [PMID: 36006410 PMCID: PMC9804384 DOI: 10.1111/mmi.14973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 07/25/2022] [Accepted: 08/10/2022] [Indexed: 01/05/2023]
Abstract
Enterobacterales have developed a specialized outer membrane polysaccharide (enterobacterial common antigen [ECA]). ECA biosynthesis begins on the cytoplasmic side of the inner membrane (IM) where glycosyltransferases sequentially add sugar moieties to form a complete repeat unit which is then translocated across the IM by WzxE before being polymerized into short linear chains by WzyE/WzzE. Research into WecG, the enzyme responsible for generating ECA lipid-II, has not progressed beyond Barr et al. (1988) who described WecG as a membrane protein. Here we revise our understanding of WecG and re-characterize it as a peripherally associated membrane protein. Through the use of Western immunoblotting we show that WecG in Shigella flexneri is maintained to the IM via its three C-terminal helices and further identify key residues in helix II which are critical for this interaction which has allowed us to identify WecG as a GT-E glycosyltransferase. We investigate the possibility of protein complexes and ultimately show that ECA lipid-I maintains WecG to the membrane which is crucial for its function. This research is the first since Barr et al. (1988) to investigate the biochemistry of WecG and reveals possible novel drug targets to inhibit WecG and thus ECA function and cell viability.
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Affiliation(s)
- Nicholas Maczuga
- Department of Molecular and Biomedical Sciences, Research Centre for Infectious Diseases, School of Biological SciencesThe University of AdelaideAdelaideSouth AustraliaAustralia
| | - Elizabeth N. H. Tran
- Department of Molecular and Biomedical Sciences, Research Centre for Infectious Diseases, School of Biological SciencesThe University of AdelaideAdelaideSouth AustraliaAustralia
| | - Renato Morona
- Department of Molecular and Biomedical Sciences, Research Centre for Infectious Diseases, School of Biological SciencesThe University of AdelaideAdelaideSouth AustraliaAustralia
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Ojima S, Ono HK, Okimoto R, Yu X, Sugiyama M, Yoshioka K, Haneda T, Okamura M, Hu DL. wecB Gene of Salmonella Gallinarum Plays a Critical Role in Systemic Infection of Fowl Typhoid. Front Microbiol 2022; 13:880932. [PMID: 35694286 PMCID: PMC9178343 DOI: 10.3389/fmicb.2022.880932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2022] [Accepted: 03/30/2022] [Indexed: 12/04/2022] Open
Abstract
Salmonella enterica serovar Gallinarum (S. Gallinarum) is a host-specific pathogen causing fowl typhoid, a severe systemic infection in poultry, which leads to substantial economic losses due to high morbidity and mortality in many developing countries. However, less is known about the pathogenic characteristics and mechanism of S. Gallinarum-induced systemic infection in chickens. In this study, we deleted the S. Gallinarum UDP-N-acetylglucosamine-1-phosphate transferase gene, which contributes to the biosynthesis of enterobacterial common antigen (ECA), and studied the pathogenicity of this wecB::Cm strain in a chicken model of systemic infection. The wecB::Cm mutant strain showed comparable growth but lower resistance to bile acid and nalidixic acid than the wild-type strain in vitro. In the oral infection model of chickens, the virulence of the wecB::Cm strain was significantly attenuated in vivo. Chickens infected with wild-type strain showed typical clinical signs and pathological changes of fowl typhoid and died between 6 and 9 days post-infection, and the bacteria rapidly disseminated to systemic organs and increased in the livers and spleens. In contrast, the wecB::Cm mutant strain did not cause chicken death, there were no significant clinical changes, and the bacterial numbers in the liver and spleen of the chickens were significantly lower than those of the chickens infected with the wild-type strain. In addition, the expression of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and CXCLi1 in the livers of wecB::Cm-infected chickens was significantly lower than that of the chickens infected with the wild-type strain. Furthermore, the attenuated wecB::Cm strain could persistently colonize the liver and spleen at low levels for up to 25 days post-infection and could induce a protective immune response in the chickens. These results indicate that the wecB gene is an important virulence factor of S. Gallinarum in the chicken model of systemic infection, and the avirulent wecB::Cm mutant could possibly be used as a live-attenuated vaccine strain for controlling fowl typhoid.
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Affiliation(s)
- Shinjiro Ojima
- Laboratory of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Hisaya K. Ono
- Laboratory of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Ryo Okimoto
- Laboratory of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Xiaoying Yu
- Laboratory of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
- College of Animal Science, Jilin Agricultural University, Changchun, China
| | - Makoto Sugiyama
- Laboratory of Veterinary Anatomy, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Kazuki Yoshioka
- Laboratory of Veterinary Anatomy, Kitasato University School of Veterinary Medicine, Towada, Japan
| | - Takeshi Haneda
- Laboratory of Microbiology, Kitasato University School of Pharmacy, Tokyo, Japan
| | - Masashi Okamura
- Section of Applied Veterinary Sciences, Division of Veterinary Sciences, Department of Veterinary Medicine, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Japan
| | - Dong-Liang Hu
- Laboratory of Zoonoses, Kitasato University School of Veterinary Medicine, Towada, Japan
- *Correspondence: Dong-Liang Hu
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Interdependence of Shigella flexneri O Antigen and Enterobacterial Common Antigen Biosynthetic Pathways. J Bacteriol 2022; 204:e0054621. [PMID: 35293778 DOI: 10.1128/jb.00546-21] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Outer membrane (OM) polysaccharides allow bacteria to resist harsh environmental conditions and antimicrobial agents, traffic to and persist in pathogenic niches, and evade immune responses. Shigella flexneri has two OM polysaccharide populations, being enterobacterial common antigen (ECA) and lipopolysaccharide (LPS) O antigen (Oag); both are polymerized into chains by separate homologs of the Wzy-dependent pathway. The two polysaccharide pathways, along with peptidoglycan (PG) biosynthesis, compete for the universal biosynthetic membrane anchor, undecaprenyl phosphate (Und-P), as the finite pool of available Und-P is critical in all three cell wall biosynthetic pathways. Interactions between the two OM polysaccharide pathways have been proposed in the past where, through the use of mutants in both pathways, various perturbations have been observed. Here, we show for the first time that mutations in one of the two OM polysaccharide pathways can affect each other, dependent on where the mutation lies along the pathway, while the second pathway remains genetically intact. We then expand on this and show that the mutations also affect PG biosynthesis pathways and provide data which supports that the classical mutant phenotypes of cell wall mutants are due to a lack of available Und-P. Our work here provides another layer in understanding the complex intricacies of the cell wall biosynthetic pathways and demonstrates their interdependence on Und-P, the universal biosynthetic membrane anchor. IMPORTANCE Bacterial outer membrane polysaccharides play key roles in a range of bacterial activities from homeostasis to virulence. Two such OM polysaccharide populations are ECA and LPS Oag, which are synthesized by separate homologs of the Wzy-dependent pathway. Both ECA and LPS Oag biosynthesis join with PG biosynthesis to form the cell wall biosynthetic pathways, which all are interdependent on the availability of Und-P for proper function. Our data show the direct effects of cell wall pathway mutations affecting all related pathways when they themselves remain genetically unchanged. This work furthers our understanding of the complexities and interdependence of the three cell wall pathways.
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10
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Masoura M, Milner MT, Overton TW, Gkatzionis K, Lund PA. Use of Transposon Directed Insertion-Site Sequencing to Probe the Antibacterial Mechanism of a Model Honey on E. coli K-12. Front Microbiol 2022; 12:803307. [PMID: 35111142 PMCID: PMC8803141 DOI: 10.3389/fmicb.2021.803307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 11/19/2021] [Indexed: 12/13/2022] Open
Abstract
Antimicrobial resistance is an ever-growing health concern worldwide that has created renewed interest in the use of traditional anti-microbial treatments, including honey. However, understanding the underlying mechanism of the anti-microbial action of honey has been hampered due to the complexity of its composition. High throughput genetic tools could assist in understanding this mechanism. In this study, the anti-bacterial mechanism of a model honey, made of sugars, hydrogen peroxide, and gluconic acid, was investigated using genome-wide transposon mutagenesis combined with high-throughput sequencing (TraDIS), with the strain Escherichia coli K-12 MG1655 as the target organism. We identified a number of genes which when mutated caused a severe loss of fitness when cells were exposed to the model honey. These genes encode membrane proteins including those involved in uptake of essential molecules, and components of the electron transport chain. They are enriched for pathways involved in intracellular homeostasis and redox activity. Genes involved in assembly and activity of formate dehydrogenase O (FDH-O) were of particular note. The phenotypes of mutants in a subset of the genes identified were confirmed by phenotypic screening of deletion strains. We also found some genes which when mutated led to enhanced resistance to treatment with the model honey. This study identifies potential synergies between the main honey stressors and provides insights into the global antibacterial mechanism of this natural product.
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Affiliation(s)
- Maria Masoura
- School of Chemical Engineering, University of Birmingham, Birmingham, United Kingdom
- Institute of Microbiology and Infection (IMI), University of Birmingham, Birmingham, United Kingdom
| | - Mathew T. Milner
- Institute of Microbiology and Infection (IMI), University of Birmingham, Birmingham, United Kingdom
| | - Tim W. Overton
- School of Chemical Engineering, University of Birmingham, Birmingham, United Kingdom
| | - Konstantinos Gkatzionis
- School of Chemical Engineering, University of Birmingham, Birmingham, United Kingdom
- Department of Food Science and Nutrition, School of the Environment, University of the Aegean, Lemnos, Greece
| | - Peter A. Lund
- Institute of Microbiology and Infection (IMI), University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Peter A. Lund,
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11
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Olivar-Casique IB, Medina-Aparicio L, Mayo S, Gama-Martínez Y, Rebollar-Flores JE, Martínez-Batallar G, Encarnación S, Calva E, Hernández-Lucas I. The human bile salt sodium deoxycholate induces metabolic and cell envelope changes in Salmonella Typhi leading to bile resistance. J Med Microbiol 2022; 71. [PMID: 35006066 DOI: 10.1099/jmm.0.001461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Introduction. Salmonella enterica serovar Typhi (S. Typhi) is the etiological agent of typhoid fever. To establish an infection in the human host, this pathogen must survive the presence of bile salts in the gut and gallbladder.Hypothesis. S. Typhi uses multiple genetic elements to resist the presence of human bile.Aims. To determine the genetic elements that S. Typhi utilizes to tolerate the human bile salt sodium deoxycholate.Methodology. A collection of S. Typhi mutant strains was evaluated for their ability to growth in the presence of sodium deoxycholate and ox-bile. Additionally, transcriptomic and proteomic responses elicited by sodium deoxycholate on S. Typhi cultures were also analysed.Results. Multiple transcriptional factors and some of their dependent genes involved in central metabolism, as well as in cell envelope, are required for deoxycholate resistance.Conclusion. These findings suggest that metabolic adaptation to bile is focused on enhancing energy production to sustain synthesis of cell envelope components exposed to damage by bile salts.
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Affiliation(s)
- Isaac B Olivar-Casique
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Liliana Medina-Aparicio
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Selena Mayo
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Yitzel Gama-Martínez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Javier E Rebollar-Flores
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Gabriel Martínez-Batallar
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Sergio Encarnación
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Edmundo Calva
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
| | - Ismael Hernández-Lucas
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México
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12
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ElyC and Cyclic Enterobacterial Common Antigen Regulate Synthesis of Phosphoglyceride-Linked Enterobacterial Common Antigen. mBio 2021; 12:e0284621. [PMID: 34809459 PMCID: PMC8609368 DOI: 10.1128/mbio.02846-21] [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] [Indexed: 12/15/2022] Open
Abstract
The Gram-negative cell envelope is a complex structure delineating the cell from its environment. Recently, we found that enterobacterial common antigen (ECA) plays a role maintaining the outer membrane (OM) permeability barrier, which excludes toxic molecules including many antibiotics. ECA is a conserved carbohydrate found throughout Enterobacterales (e.g., Salmonella, Klebsiella, and Yersinia). There are two OM forms of ECA (phosphoglyceride-linked ECAPG and lipopolysaccharide-linked ECALPS) and one periplasmic form of ECA (cyclic ECACYC). ECAPG, found in the outer leaflet of the OM, consists of a linear ECA oligomer attached to phosphoglyceride through a phosphodiester linkage. The process through which ECAPG is produced from polymerized ECA is unknown. Therefore, we set out to identify genes interacting genetically with ECAPG biosynthesis in Escherichia coli K-12 using the competition between ECA and peptidoglycan biosynthesis. Through transposon-directed insertion sequencing, we identified an interaction between elyC and ECAPG biosynthesis. ElyC is an inner membrane protein previously shown to alter peptidoglycan biosynthesis rates. We found ΔelyC was lethal specifically in strains producing ECAPG without other ECA forms, suggesting ECAPG biosynthesis impairment or dysregulation. Further characterization suggested ElyC inhibits ECAPG synthesis in a posttranscriptional manner. Moreover, the full impact of ElyC on ECA levels requires the presence of ECACYC. Our data demonstrate ECACYC can regulate ECAPG synthesis in strains wild type for elyC. Overall, our data demonstrate ElyC and ECACYC act in a novel pathway that regulates the production of ECAPG, supporting a model in which ElyC provides feedback regulation of ECAPG production based on the periplasmic levels of ECACYC.
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Increased Production of Colanic Acid by an Engineered Escherichia coli Strain, Mediated by Genetic and Environmental Perturbations. Appl Biochem Biotechnol 2021; 193:4083-4096. [PMID: 34542821 DOI: 10.1007/s12010-021-03671-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2021] [Accepted: 09/03/2021] [Indexed: 10/20/2022]
Abstract
Colanic acid (CA) is a major exopolysaccharide synthesized by Escherichia coli that serves as a constituent of biofilm matrices. CA demonstrates potential applications in the food, cosmetics, and pharmaceutical industry. Moreover, L-fucose, a monomeric constituent of CA, exhibits various physiological activities, such as antitumor, anti-inflammatory, and skin-whitening. Here, the effects of genetic and environmental perturbations were investigated for improving CA production by E. coli. When rcsF, a positive regulator gene of CA synthesis, was expressed in E. coli ΔwaaF, a CA-producing strain constructed previously, the CA titer increased to 3051.2 mg/L as compared to 2052.8 mg/L observed with E. coli ΔwaaF. Among the environmental factors tested, namely, osmotic and oxidative stresses and pH, pH was a primary factor that significantly improved CA production. When the pH of the culture medium of E. coli ΔwaaF + rcsF was maintained at 7, the CA titer significantly increased to 4351.6 mg/L. The CA yield obtained with E. coli ΔwaaF + rcsF grown at pH 7 was 5180.4 mg CA/g dry cell weight, which is the highest yield of CA reported so far. This engineered E. coli system with optimization of environmental conditions can be employed for fast and economically-feasible production of CA.
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The Rcs Stress Response System Regulator GumB Modulates Serratia marcescens-Induced Inflammation and Bacterial Proliferation in a Rabbit Keratitis Model and Cytotoxicity In Vitro. Infect Immun 2021; 89:e0011121. [PMID: 33820815 DOI: 10.1128/iai.00111-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In this study, we tested the hypothesis that the conserved bacterial IgaA-family protein, GumB, mediates microbial pathogenesis associated with Serratia marcescens ocular infections through regulation of the Rcs stress response system. The role of the Rcs system and bacterial stress response systems for microbial keratitis is not known, and the role of IgaA proteins in mammalian pathogenesis models has only been tested with partial-function allele variants of Salmonella. Here, we observed that an Rcs-activated gumB mutant had a >50-fold reduction in proliferation compared to the wild type within rabbit corneas at 48 h and demonstrated a notable reduction in inflammation based on inflammatory signs, including the absence of hypopyons, and proinflammatory markers measured at the RNA and protein levels. The gumB mutant phenotypes could be complemented by wild-type gumB on a plasmid. We observed that bacteria with an inactivated Rcs stress response system induced high levels of ocular inflammation and restored corneal virulence to the gumB mutant. The high virulence of the ΔrcsB mutant was dependent upon the ShlA cytolysin transporter ShlB. Similar results were found for testing the cytotoxic effects of wild-type and mutant bacteria on a human corneal epithelial cell line in vitro. Together, these data indicate that GumB regulates virulence factor production through the Rcs system, and this overall stress response system is a key mediator of a bacterium's ability to induce vision-threatening keratitis.
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Qiao J, Tan X, Huang D, Li H, Wang Z, Ren H, Hu X, Wang X. Construction and Application of an Escherichia coli Strain Lacking 62 Genes Responsible for the Biosynthesis of Enterobacterial Common Antigen and Flagella. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2021; 69:4153-4163. [PMID: 33787256 DOI: 10.1021/acs.jafc.1c00453] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The biosynthesis of the enterobacterial common antigen and flagella in Escherichia coli consumes lots of substrates and energy. In this study, 12 genes responsible for the biosynthesis of the enterobacterial common antigen were deleted in E. coli MG1655, resulting in WQM021. WQM021 grew better than MG1655 in both rich LB medium and minimum M9 medium. Compared with MG1655, WQM021 showed higher membrane permeability and higher production efficiency for recombinant proteins, polyhydroxyalkanoate, and l-threonine. Transcriptome analysis revealed that genes relevant to glucose consumption, glycolysis, and flagellar synthesis were significantly upregulated in WQM021. Therefore, 50 genes responsible for flagellar biosynthesis were further deleted in WQM021, resulting in WQM022. WQM022 grew better and could synthesize more polyhydroxyalkanoate and l-threonine than WQM021. The results demonstrate that the productivity of E. coli can be efficiently improved when the enterobacterial common antigen and flagella are eliminated. This strategy has guiding significance in the optimization of other industrial products and microorganisms.
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Affiliation(s)
- Jun Qiao
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xin Tan
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Danyang Huang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Hedan Li
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Zhen Wang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Hongyu Ren
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
| | - Xiaoqing Hu
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi 214122, China
| | - Xiaoyuan Wang
- State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China
- International Joint Laboratory on Food Safety, Jiangnan University, Wuxi 214122, China
- Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China
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16
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Jiang X, Tan WB, Shrivastava R, Seow DCS, Chen SL, Guan XL, Chng SS. Mutations in enterobacterial common antigen biosynthesis restore outer membrane barrier function in Escherichia coli tol-pal mutants. Mol Microbiol 2020; 114:991-1005. [PMID: 32808719 DOI: 10.1111/mmi.14590] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2020] [Revised: 08/12/2020] [Indexed: 12/27/2022]
Abstract
The outer membrane (OM) is an essential component of the Gram-negative bacterial envelope that protects the cells against external threats. To maintain a functional OM, cells require distinct mechanisms to ensure balance of proteins and lipids in the membrane. Mutations in OM biogenesis and/or homeostasis pathways often result in permeability defects, but how molecular changes in the OM affect barrier function is unclear. Here, we seek potential mechanism(s) that can alleviate permeability defects in Escherichia coli cells lacking the Tol-Pal complex, which accumulate excess PLs in the OM. We identify mutations in enterobacterial common antigen (ECA) biosynthesis that re-establish OM barrier function against large hydrophilic molecules, yet did not restore lipid homeostasis. Furthermore, we demonstrate that build-up of biosynthetic intermediates, but not loss of ECA itself, contributes to the rescue. This suppression of OM phenotypes is unrelated to known effects that accumulation of ECA intermediates have on the cell wall. Finally, we reveal that an unusual diacylglycerol pyrophosphoryl-linked lipid species also accumulates in ECA mutants, and might play a role in the rescue phenotype. Our work provides insights into how OM barrier function can be restored independent of lipid homeostasis, and highlights previously unappreciated effects of ECA-related species in OM biology.
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Affiliation(s)
- Xiang'Er Jiang
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Wee Boon Tan
- Singapore Center for Environmental Life Sciences Engineering, National University of Singapore (SCELSE-NUS), Singapore, Singapore
| | - Rahul Shrivastava
- Department of Chemistry, National University of Singapore, Singapore, Singapore
| | - Deborah Chwee San Seow
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Swaine Lin Chen
- Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.,Genome Institute of Singapore, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Xue Li Guan
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Shu-Sin Chng
- Department of Chemistry, National University of Singapore, Singapore, Singapore.,Singapore Center for Environmental Life Sciences Engineering, National University of Singapore (SCELSE-NUS), Singapore, Singapore
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17
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Abstract
The outer membrane (OM) of Gram-negative bacteria poses a barrier to antibiotic entry due to its high impermeability. Thus, there is an urgent need to study the function and biogenesis of the OM. In Enterobacterales, an order of bacteria with many pathogenic members, one of the components of the OM is enterobacterial common antigen (ECA). We have known of the presence of ECA on the cell surface of Enterobacterales for many years, but its properties have only more recently begun to be unraveled. ECA is a carbohydrate antigen built of repeating units of three amino sugars, the structure of which is conserved throughout Enterobacterales. There are three forms of ECA, two of which (ECAPG and ECALPS) are located on the cell surface, while one (ECACYC) is located in the periplasm. Awareness of the importance of ECA has increased due to studies of its function that show it plays a vital role in bacterial physiology and interaction with the environment. Here, we review the discovery of ECA, the pathways for the biosynthesis of ECA, and the interactions of its various forms. In addition, we consider the role of ECA in the host immune response, as well as its potential roles in host-pathogen interaction. Furthermore, we explore recent work that offers insights into the cellular function of ECA. This review provides a glimpse of the biological significance of this enigmatic molecule.
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Affiliation(s)
- Ashutosh K Rai
- Department of Biology, Texas A&M University, College Station, Texas, USA
| | - Angela M Mitchell
- Department of Biology, Texas A&M University, College Station, Texas, USA
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Park J, Tae Eom G, Young Oh J, Hyun Park J, Chang Kim S, Kwang Song J, Hoon Ahn J. High-Level Production of Bacteriotoxic Phospholipase A1 in Bacterial Host Pseudomonas fluorescens Via ABC Transporter-Mediated Secretion and Inducible Expression. Microorganisms 2020; 8:microorganisms8020239. [PMID: 32053917 PMCID: PMC7074900 DOI: 10.3390/microorganisms8020239] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Revised: 02/05/2020] [Accepted: 02/09/2020] [Indexed: 02/03/2023] Open
Abstract
Bacterial phospholipase A1 (PLA1) is used in various industrial fields because it can catalyze the hydrolysis, esterification, and transesterification of phospholipids to their functional derivatives. It also has a role in the degumming process of crude plant oils. However, bacterial expression of the foreign PLA1-encoding gene was generally hampered because intracellularly expressed PLA1 is inherently toxic and damages the phospholipid membrane. In this study, we report that secretion-based production of recombinant PlaA, a bacterial PLA1 gene, or co-expression of PlaS, an accessory gene, minimizes this harmful effect. We were able to achieve high-level PlaA production via secretion-based protein production. Here, TliD/TliE/TliF, an ABC transporter complex of Pseudomonas fluorescens SIK-W1, was used to secrete recombinant proteins to the extracellular medium. In order to control the protein expression with induction, a new strain of P. fluorescens, which had the lac operon repressor gene lacI, was constructed and named ZYAI strain. The bacteriotoxic PlaA protein was successfully produced in a bacterial host, with help from ABC transporter-mediated secretion, induction-controlled protein expression, and fermentation. The final protein product is capable of degumming oil efficiently, signifying its application potential.
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Affiliation(s)
- Jiyeon Park
- Korea Science Academy of Korea Advanced Institute of Science and Technology, Busan 47162, Korea;
- Intelligent Synthetic Biology Center, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea;
| | - Gyeong Tae Eom
- Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT) 1, Ulsan 44429, Korea;
| | - Joon Young Oh
- Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea; (J.Y.O.); (J.H.P.); (J.K.S.)
| | - Ji Hyun Park
- Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea; (J.Y.O.); (J.H.P.); (J.K.S.)
| | - Sun Chang Kim
- Intelligent Synthetic Biology Center, 291 Daehak-ro, Yuseong-gu, Daejeon 305-701, Korea;
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Jae Kwang Song
- Research Center for Bio-based Chemistry, Korea Research Institute of Chemical Technology (KRICT), Daejeon 34114, Korea; (J.Y.O.); (J.H.P.); (J.K.S.)
| | - Jung Hoon Ahn
- Korea Science Academy of Korea Advanced Institute of Science and Technology, Busan 47162, Korea;
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
- Correspondence: ; Tel.: +82-51-606-2335
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Anderson MT, Mitchell LA, Sintsova A, Rice KA, Mobley HLT. Sulfur Assimilation Alters Flagellar Function and Modulates the Gene Expression Landscape of Serratia marcescens. mSystems 2019; 4:e00285-19. [PMID: 31387930 PMCID: PMC6687942 DOI: 10.1128/msystems.00285-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/24/2019] [Indexed: 11/29/2022] Open
Abstract
Sulfur is an essential nutrient that contributes to cellular redox homeostasis, transcriptional regulation, and translation initiation when incorporated into different biomolecules. Transport and reduction of extracellular sulfate followed by cysteine biosynthesis is a major pathway of bacterial sulfur assimilation. For the opportunistic pathogen Serratia marcescens, function of the cysteine biosynthesis pathway is required for extracellular phospholipase activity and flagellum-mediated surface motility, but little else is known about the influence of sulfur assimilation on the physiology of this organism. In this work, it was determined that an S. marcescens cysteine auxotroph fails to differentiate into hyperflagellated and elongated swarmer cells and that cysteine, but not other organic sulfur molecules, restores swarming motility to these bacteria. The S. marcescens cysteine auxotroph further exhibits reduced transcription of phospholipase, hemolysin, and flagellin genes, each of which is subject to transcriptional control by the flagellar regulatory system. Based on these data and the central role of cysteine in sulfur assimilation, it was reasoned that environmental sulfur availability may contribute to the regulation of these functions in S. marcescens Indeed, bacteria that are starved for sulfate exhibit substantially reduced transcription of the genes for hemolysin, phospholipase, and the FlhD flagellar master regulator. A global transcriptomic analysis further defined a large set of S. marcescens genes that are responsive to extracellular sulfate availability, including genes that encode membrane transport, nutrient utilization, and metabolism functions. Finally, sulfate availability was demonstrated to alter S. marcescens cytolytic activity, suggesting that sulfate assimilation may impact the virulence of this organism.IMPORTANCE Serratia marcescens is a versatile bacterial species that inhabits diverse environmental niches and is capable of pathogenic interactions with host organisms ranging from insects to humans. This report demonstrates for the first time the extensive impacts that environmental sulfate availability and cysteine biosynthesis have on the transcriptome of S. marcescens The finding that greater than 1,000 S. marcescens genes are differentially expressed depending on sulfate availability suggests that sulfur abundance is a crucial factor that controls the physiology of this organism. Furthermore, the high relative expression levels for the putative virulence factors flagella, phospholipase, and hemolysin in the presence of sulfate suggests that a sulfur-rich host environment could contribute to the transcription of these genes during infection.
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Affiliation(s)
- Mark T Anderson
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Lindsay A Mitchell
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Anna Sintsova
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Katherine A Rice
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Harry L T Mobley
- Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA
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20
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Rcs Phosphorelay Activation in Cardiolipin-Deficient Escherichia coli Reduces Biofilm Formation. J Bacteriol 2019; 201:JB.00804-18. [PMID: 30782633 DOI: 10.1128/jb.00804-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Accepted: 02/07/2019] [Indexed: 11/20/2022] Open
Abstract
Biofilm formation is a complex process that requires a number of transcriptional, proteomic, and physiological changes to enable bacterial survival. The lipid membrane presents a barrier to communication between the machinery within bacteria and the physical and chemical features of their extracellular environment, and yet little is known about how the membrane influences biofilm development. We found that depleting the anionic phospholipid cardiolipin reduces biofilm formation in Escherichia coli cells by as much as 50%. The absence of cardiolipin activates the regulation of colanic acid synthesis (Rcs) envelope stress response, which represses the production of flagella, disrupts initial biofilm attachment, and reduces biofilm growth. We demonstrate that a reduction in the concentration of cardiolipin impairs translocation of proteins across the inner membrane, which we hypothesize activates the Rcs pathway through the outer membrane lipoprotein RcsF. Our study demonstrates a molecular connection between the composition of membrane phospholipids and biofilm formation in E. coli and suggests that altering lipid biosynthesis may be a viable approach for altering biofilm formation and possibly other multicellular phenotypes related to bacterial adaptation and survival.IMPORTANCE There is a growing interest in the role of lipid membrane composition in the physiology and adaptation of bacteria. We demonstrate that a reduction in the anionic phospholipid cardiolipin impairs biofilm formation in Escherichia coli cells. Depleting cardiolipin reduced protein translocation across the inner membrane and activated the Rcs envelope stress response. Consequently, cardiolipin depletion produced cells lacking assembled flagella, which impacted their ability to attach to surfaces and seed the earliest stage in biofilm formation. This study provides empirical evidence for the role of anionic phospholipid homeostasis in protein translocation and its effect on biofilm development and highlights modulation of the membrane composition as a potential method of altering bacterial phenotypes related to adaptation and survival.
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21
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Conley ZC, Carlson-Banning KM, Carter AG, de la Cova A, Song Y, Zechiedrich L. Sugar and iron: Toward understanding the antibacterial effect of ciclopirox in Escherichia coli. PLoS One 2019; 14:e0210547. [PMID: 30633761 PMCID: PMC6329577 DOI: 10.1371/journal.pone.0210547] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Accepted: 12/27/2018] [Indexed: 12/11/2022] Open
Abstract
New antibiotics are needed against antibiotic-resistant gram-negative bacteria. The repurposed antifungal drug, ciclopirox, equally blocks antibiotic-susceptible or multidrug-resistant Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae clinical isolates, indicating that it is not affected by existing resistance mechanisms. Toward understanding how ciclopirox blocks growth, we screened E. coli mutant strains and found that disruption of genes encoding products involved in galactose salvage, enterobacterial common antigen synthesis, and transport of the iron binding siderophore, enterobactin, lowered the minimum inhibitory concentration of ciclopirox needed to block growth of the mutant compared to the isogenic parent strain. We found that ciclopirox induced enterobactin production and that this effect is strongly affected by the deletion of the galactose salvage genes encoding UDP-galactose 4-epimerase, galE, or galactose-1-phosphate uridylyltransferase, galT. As disruption of ECA synthesis activates the regulation of capsular synthesis (Rcs) phosphorelay, which inhibits bacterial swarming and promotes biofilm development, we test whether ciclopirox prevents activation of the Rcs pathway. Sub-inhibitory concentrations of ciclopirox increased swarming of the E. coli laboratory K12 strain BW25113 but had widely varying effects on swarming or surface motility of clinical isolate E. coli, A. baumannii, and K. pneumoniae. There was no effect of ciclopirox on biofilm production, suggesting it does not target Rcs. Altogether, our data suggest ciclopirox-mediated alteration of lipopolysaccharides stimulates enterobactin production and affects bacterial swarming.
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Affiliation(s)
- Zachary C. Conley
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Kimberly M. Carlson-Banning
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Ashley G. Carter
- Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Alejandro de la Cova
- Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
- Center for Environmental and Human Toxicology, University of Florida College of Veterinary Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Yongcheng Song
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Lynn Zechiedrich
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Virology and Microbiology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Pharmacology and Chemical Biology, Baylor College of Medicine, Houston, Texas, United States of America
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22
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Dorman MJ, Feltwell T, Goulding DA, Parkhill J, Short FL. The Capsule Regulatory Network of Klebsiella pneumoniae Defined by density-TraDISort. mBio 2018; 9:e01863-18. [PMID: 30459193 PMCID: PMC6247091 DOI: 10.1128/mbio.01863-18] [Citation(s) in RCA: 63] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/08/2018] [Indexed: 01/04/2023] Open
Abstract
Klebsiella pneumoniae infections affect infants and the immunocompromised, and the recent emergence of hypervirulent and multidrug-resistant K. pneumoniae lineages is a critical health care concern. Hypervirulence in K. pneumoniae is mediated by several factors, including the overproduction of extracellular capsule. However, the full details of how K. pneumoniae capsule biosynthesis is achieved or regulated are not known. We have developed a robust and sensitive procedure to identify genes influencing capsule production, density-TraDISort, which combines density gradient centrifugation with transposon insertion sequencing. We have used this method to explore capsule regulation in two clinically relevant Klebsiella strains, K. pneumoniae NTUH-K2044 (capsule type K1) and K. pneumoniae ATCC 43816 (capsule type K2). We identified multiple genes required for full capsule production in K. pneumoniae, as well as putative suppressors of capsule in NTUH-K2044, and have validated the results of our screen with targeted knockout mutants. Further investigation of several of the K. pneumoniae capsule regulators identified-ArgR, MprA/KvrB, SlyA/KvrA, and the Sap ABC transporter-revealed effects on capsule amount and architecture, serum resistance, and virulence. We show that capsule production in K. pneumoniae is at the center of a complex regulatory network involving multiple global regulators and environmental cues and that the majority of capsule regulatory genes are located in the core genome. Overall, our findings expand our understanding of how capsule is regulated in this medically important pathogen and provide a technology that can be easily implemented to study capsule regulation in other bacterial species.IMPORTANCE Capsule production is essential for K. pneumoniae to cause infections, but its regulation and mechanism of synthesis are not fully understood in this organism. We have developed and applied a new method for genome-wide identification of capsule regulators. Using this method, many genes that positively or negatively affect capsule production in K. pneumoniae were identified, and we use these data to propose an integrated model for capsule regulation in this species. Several of the genes and biological processes identified have not previously been linked to capsule synthesis. We also show that the methods presented here can be applied to other species of capsulated bacteria, providing the opportunity to explore and compare capsule regulatory networks in other bacterial strains and species.
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Affiliation(s)
- Matthew J Dorman
- Wellcome Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Theresa Feltwell
- Wellcome Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - David A Goulding
- Wellcome Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Julian Parkhill
- Wellcome Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
| | - Francesca L Short
- Wellcome Sanger Institute, Hinxton, Cambridgeshire, United Kingdom
- Department of Medicine, University of Cambridge, Cambridge, United Kingdom
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Swarmer Cell Development of the Bacterium Proteus mirabilis Requires the Conserved Enterobacterial Common Antigen Biosynthesis Gene rffG. J Bacteriol 2018; 200:JB.00230-18. [PMID: 29967121 DOI: 10.1128/jb.00230-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Accepted: 06/27/2018] [Indexed: 01/01/2023] Open
Abstract
Individual cells of the bacterium Proteus mirabilis can elongate up to 40-fold on surfaces before engaging in a cooperative surface-based motility termed swarming. How cells regulate this dramatic morphological remodeling remains an open question. In this paper, we move forward the understanding of this regulation by demonstrating that P. mirabilis requires the gene rffG for swarmer cell elongation and subsequent swarm motility. The rffG gene encodes a protein homologous to the dTDP-glucose 4,6-dehydratase protein of Escherichia coli, which contributes to enterobacterial common antigen biosynthesis. Here, we characterize the rffG gene in P. mirabilis, demonstrating that it is required for the production of large lipopolysaccharide-linked moieties necessary for wild-type cell envelope integrity. We show that the absence of the rffG gene induces several stress response pathways, including those controlled by the transcriptional regulators RpoS, CaiF, and RcsB. We further show that in rffG-deficient cells, the suppression of the Rcs phosphorelay, via loss of RcsB, is sufficient to induce cell elongation and swarm motility. However, the loss of RcsB does not rescue cell envelope integrity defects and instead results in abnormally shaped cells, including cells producing more than two poles. We conclude that an RcsB-mediated response acts to suppress the emergence of shape defects in cell envelope-compromised cells, suggesting an additional role for RcsB in maintaining cell morphology under stress conditions. We further propose that the composition of the cell envelope acts as a checkpoint before cells initiate swarmer cell elongation and motility.IMPORTANCEProteus mirabilis swarm motility has been implicated in pathogenesis. We have found that cells deploy multiple uncharacterized strategies to handle cell envelope stress beyond the Rcs phosphorelay when attempting to engage in swarm motility. While RcsB is known to directly inhibit the master transcriptional regulator for swarming, we have shown an additional role for RcsB in protecting cell morphology. These data support a growing appreciation that the Rcs phosphorelay is a multifunctional regulator of cell morphology in addition to its role in microbial stress responses. These data also strengthen the paradigm that outer membrane composition is a crucial checkpoint for modulating entry into swarm motility. Furthermore, the rffG-dependent moieties provide a novel attractive target for potential antimicrobials.
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Cyclic Enterobacterial Common Antigen Maintains the Outer Membrane Permeability Barrier of Escherichia coli in a Manner Controlled by YhdP. mBio 2018; 9:mBio.01321-18. [PMID: 30087168 PMCID: PMC6083912 DOI: 10.1128/mbio.01321-18] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Gram-negative bacteria have an outer membrane (OM) impermeable to many toxic compounds that can be further strengthened during stress. In Enterobacteriaceae, the envelope contains enterobacterial common antigen (ECA), a carbohydrate-derived moiety conserved throughout Enterobacteriaceae, the function of which is poorly understood. Previously, we identified several genes in Escherichia coli K-12 responsible for an RpoS-dependent decrease in envelope permeability during carbon-limited stationary phase. For one of these, yhdP, a gene of unknown function, deletion causes high levels of both vancomycin and detergent sensitivity, independent of growth phase. We isolated spontaneous suppressor mutants of yhdP with loss-of-function mutations in the ECA biosynthesis operon. ECA biosynthesis gene deletions suppressed envelope permeability from yhdP deletion independently of envelope stress responses and interactions with other biosynthesis pathways, demonstrating suppression is caused directly by removing ECA. Furthermore, yhdP deletion changed cellular ECA levels and yhdP was found to co-occur phylogenetically with the ECA biosynthesis operon. Cells make three forms of ECA: ECA lipopolysaccharide (LPS), an ECA chain linked to LPS core; ECA phosphatidylglycerol, a surface-exposed ECA chain linked to phosphatidylglycerol; and cyclic ECA, a cyclized soluble ECA molecule found in the periplasm. We determined that the suppression of envelope permeability with yhdP deletion is caused specifically by the loss of cyclic ECA, despite lowered levels of this molecule found with yhdP deletion. Furthermore, removing cyclic ECA from wild-type cells also caused changes to OM permeability. Our data demonstrate cyclic ECA acts to maintain the OM permeability barrier in a manner controlled by YhdP. Enterobacterial common antigen (ECA) is a surface antigen made by all members of Enterobacteriaceae, including many clinically relevant genera (e.g., Escherichia, Klebsiella, Yersinia). Although this surface-exposed molecule is conserved throughout Enterobacteriaceae, very few functions have been ascribed to it. Here, we have determined that the periplasmic form of ECA, cyclic ECA, plays a role in maintaining the outer membrane permeability barrier. This activity is controlled by a protein of unknown function, YhdP, and deletion of yhdP damages the OM permeability barrier in a cyclic ECA-dependent manner, allowing harmful molecules such as antibiotics into the cell. This role in maintenance of the envelope permeability barrier is the first time a phenotype has been described for cyclic ECA. As the Gram-negative envelope is generally impermeable to antibiotics, understanding the mechanisms through which the barrier is maintained and antibiotics are excluded may lead to improved antibiotic delivery.
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An IgaA/UmoB Family Protein from Serratia marcescens Regulates Motility, Capsular Polysaccharide Biosynthesis, and Secondary Metabolite Production. Appl Environ Microbiol 2018; 84:AEM.02575-17. [PMID: 29305504 DOI: 10.1128/aem.02575-17] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 12/23/2017] [Indexed: 12/28/2022] Open
Abstract
Secondary metabolites are an important source of pharmaceuticals and key modulators of microbe-microbe interactions. The bacterium Serratia marcescens is part of the Enterobacteriaceae family of eubacteria and produces a number of biologically active secondary metabolites. In this study, we screened for novel regulators of secondary metabolites synthesized by a clinical isolate of S. marcescens and found mutations in a gene for an uncharacterized UmoB/IgaA family member here named gumB Mutation of gumB conferred a severe loss of the secondary metabolites prodigiosin and serratamolide. The gumB mutation conferred pleiotropic phenotypes, including altered biofilm formation, highly increased capsular polysaccharide production, and loss of swimming and swarming motility. These phenotypes corresponded to transcriptional changes in fimA, wecA, and flhD Unlike other UmoB/IgaA family members, gumB was found to be not essential for growth in S. marcescens, yet igaA from Salmonella enterica, yrfF from Escherichia coli, and an uncharacterized predicted ortholog from Klebsiella pneumoniae complemented the gumB mutant secondary metabolite defects, suggesting highly conserved function. These data support the idea that UmoB/IgaA family proteins are functionally conserved and extend the known regulatory influence of UmoB/IgaA family proteins to the control of competition-associated secondary metabolites and biofilm formation.IMPORTANCE IgaA/UmoB family proteins are found in members of the Enterobacteriaceae family of bacteria, which are of environmental and public health importance. IgaA/UmoB family proteins are thought to be inner membrane proteins that report extracellular stresses to intracellular signaling pathways that respond to environmental challenge. This study introduces a new member of the IgaA/UmoB family and demonstrates a high degree of functional similarity between IgaA/UmoB family proteins. Moreover, this study extends the phenomena controlled by IgaA/UmoB family proteins to include the biosynthesis of antimicrobial secondary metabolites.
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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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A Transcriptional Regulatory Mechanism Finely Tunes the Firing of Type VI Secretion System in Response to Bacterial Enemies. mBio 2017; 8:mBio.00559-17. [PMID: 28830939 PMCID: PMC5565961 DOI: 10.1128/mbio.00559-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The ability to detect and measure danger from an environmental signal is paramount for bacteria to respond accordingly, deploying strategies that halt or counteract potential cellular injury and maximize survival chances. Type VI secretion systems (T6SSs) are complex bacterial contractile nanomachines able to target toxic effectors into neighboring bacteria competing for the same colonization niche. Previous studies support the concept that either T6SSs are constitutively active or they fire effectors in response to various stimuli, such as high bacterial density, cell-cell contact, nutrient depletion, or components from dead sibling cells. For Serratia marcescens, it has been proposed that its T6SS is stochastically expressed, with no distinction between harmless or aggressive competitors. In contrast, we demonstrate that the Rcs regulatory system is responsible for finely tuning Serratia T6SS expression levels, behaving as a transcriptional rheostat. When confronted with harmless bacteria, basal T6SS expression levels suffice for Serratia to eliminate the competitor. A moderate T6SS upregulation is triggered when, according to the aggressor-prey ratio, an unbalanced interplay between homologous and heterologous effectors and immunity proteins takes place. Higher T6SS expression levels are achieved when Serratia is challenged by a contender like Acinetobacter, which indiscriminately fires heterologous effectors able to exert lethal cellular harm, threatening the survival of the Serratia population. We also demonstrate that Serratia’s RcsB-dependent T6SS regulatory mechanism responds not to general stress signals but to the action of specific effectors from competitors, displaying an exquisite strategy to weigh risks and keep the balance between energy expenditure and fitness costs. Serratia marcescens is among the health-threatening pathogens categorized by the WHO as research priorities to develop alternative antimicrobial strategies, and it was also recently identified as one major component of the gut microbiome in familial Crohn disease dysbiosis. Type VI secretion systems (T6SSs) stand among the array of survival strategies that Serratia displays. They are contractile multiprotein complexes able to deliver toxic effectors directed to kill bacterial species sharing the same niche and, thus, competing for vital resources. Here, we show that Serratia is able to detect and measure the extent of damage generated through T6SS-delivered toxins from neighboring bacteria and responds by transcriptionally adjusting the expression level of its own T6SS machinery to counterattack the rival. This strategy allows Serratia to finely tune the production of costly T6SS devices to maximize the chances of successfully fighting against enemies and minimize energy investment. The knowledge of this novel mechanism provides insight to better understand bacterial interactions and design alternative treatments for polymicrobial infections.
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Anderson MT, Mitchell LA, Mobley HLT. Cysteine Biosynthesis Controls Serratia marcescens Phospholipase Activity. J Bacteriol 2017; 199:e00159-17. [PMID: 28559296 PMCID: PMC5527384 DOI: 10.1128/jb.00159-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 05/22/2017] [Indexed: 01/01/2023] Open
Abstract
Serratia marcescens causes health care-associated opportunistic infections that can be difficult to treat due to a high incidence of antibiotic resistance. One of the many secreted proteins of S. marcescens is the PhlA phospholipase enzyme. Genes involved in the production and secretion of PhlA were identified by screening a transposon insertion library for phospholipase-deficient mutants on phosphatidylcholine-containing medium. Mutations were identified in four genes (cyaA, crp, fliJ, and fliP) that are involved in the flagellum-dependent PhlA secretion pathway. An additional phospholipase-deficient isolate harbored a transposon insertion in the cysE gene encoding a predicted serine O-acetyltransferase required for cysteine biosynthesis. The cysE requirement for extracellular phospholipase activity was confirmed using a fluorogenic phospholipase substrate. Phospholipase activity was restored to the cysE mutant by the addition of exogenous l-cysteine or O-acetylserine to the culture medium and by genetic complementation. Additionally, phlA transcript levels were decreased 6-fold in bacteria lacking cysE and were restored with added cysteine, indicating a role for cysteine-dependent transcriptional regulation of S. marcescens phospholipase activity. S. marcescenscysE mutants also exhibited a defect in swarming motility that was correlated with reduced levels of flhD and fliA flagellar regulator gene transcription. Together, these findings suggest a model in which cysteine is required for the regulation of both extracellular phospholipase activity and surface motility in S. marcescensIMPORTANCESerratia marcescens is known to secrete multiple extracellular enzymes, but PhlA is unusual in that this protein is thought to be exported by the flagellar transport apparatus. In this study, we demonstrate that both extracellular phospholipase activity and flagellar function are dependent on the cysteine biosynthesis pathway. Furthermore, a disruption of cysteine biosynthesis results in decreased phlA and flagellar gene transcription, which can be restored by supplying bacteria with exogenous cysteine. These results identify a previously unrecognized role for CysE and cysteine in the secretion of S. marcescens phospholipase and in bacterial motility.
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Affiliation(s)
- Mark T Anderson
- University of Michigan Medical School, Department of Microbiology and Immunology, Ann Arbor, Michigan, USA
| | - Lindsay A Mitchell
- University of Michigan Medical School, Department of Microbiology and Immunology, Ann Arbor, Michigan, USA
| | - Harry L T Mobley
- University of Michigan Medical School, Department of Microbiology and Immunology, Ann Arbor, Michigan, USA
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Characterization of putative virulence factors of Serratia marcescens strain SEN for pathogenesis in Spodoptera litura. J Invertebr Pathol 2017; 143:115-123. [DOI: 10.1016/j.jip.2016.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2016] [Revised: 12/09/2016] [Accepted: 12/12/2016] [Indexed: 12/20/2022]
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Effects of Lipopolysaccharide Core Sugar Deficiency on Colanic Acid Biosynthesis in Escherichia coli. J Bacteriol 2016; 198:1576-1584. [PMID: 27002133 DOI: 10.1128/jb.00094-16] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 03/12/2016] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED When 10 Escherichia coli mutant strains with defects in lipopolysaccharide (LPS) core biosynthesis were grown on agar medium at 30°C, four of them, the ΔwaaF, ΔwaaG, ΔwaaP, and ΔwaaB strains, formed mucoid colonies, while the other six, the ΔwaaU, ΔwaaR, ΔwaaO, ΔwaaC, ΔwaaQ, and ΔwaaY strains, did not. Using light microscopy with tannin mordant staining, the presence of exopolysaccharide around the cells of the mutants that formed mucoid colonies could be discerned. The ΔwaaF mutant produced the largest amounts of exopolysaccharide, regardless of whether it was grown on agar or in liquid medium. The exopolysaccharide was isolated from the liquid growth medium of ΔwaaF cells, hydrolyzed, and analyzed by high-performance liquid chromatography with an ion-exchange column, and the results indicated that the exopolysaccharide was consistent with colanic acid. When the key genes related to the biosynthesis of colanic acid, i.e., wza, wzb, wzc, and wcaA, were deleted in the ΔwaaF background, the exopolysaccharide could not be produced any more, further confirming that it was colanic acid. Colanic acid could not be produced in strains in which rcsA, rcsB, rcsD, or rcsF was deleted in the ΔwaaF background, but a reduced level of colanic acid production was detected when the rcsC gene was deleted, suggesting that a change of lipopolysaccharide structure in ΔwaaF cells might be sensed by the RcsCDB phosphorelay system, leading to the production of colanic acid. The results demonstrate that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural deficiency of lipopolysaccharide. IMPORTANCE Lipopolysaccharide and colanic acid are important forms of exopolysaccharide for Escherichia coli cells. Their metabolism and biological significance have been investigated, but their interrelation with the cell stress response process is not understood. This study demonstrates, for the first time, that E. coli cells can activate colanic acid production through the RcsCDB phosphorelay system in response to a structural change of lipopolysaccharide, suggesting that bacterial cells can monitor the outer membrane integrity, which is essential for cell survival and damage repair.
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Jorgenson MA, Kannan S, Laubacher ME, Young KD. Dead-end intermediates in the enterobacterial common antigen pathway induce morphological defects in Escherichia coli by competing for undecaprenyl phosphate. Mol Microbiol 2015; 100:1-14. [PMID: 26593043 DOI: 10.1111/mmi.13284] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/26/2015] [Indexed: 01/31/2023]
Abstract
Bacterial morphology is determined primarily by the architecture of the peptidoglycan (PG) cell wall, a mesh-like layer that encases the cell. To identify novel mechanisms that create or maintain cell shape in Escherichia coli, we used flow cytometry to screen a transposon insertion library and identified a wecE mutant that altered cell shape, causing cells to filament and swell. WecE is a sugar aminotransferase involved in the biosynthesis of enterobacterial common antigen (ECA), a non-essential outer membrane glycolipid of the Enterobacteriaceae. Loss of wecE interrupts biosynthesis of ECA and causes the accumulation of the undecaprenyl pyrophosphate-linked intermediate ECA-lipid II. The wecE shape defects were reversed by: (i) preventing initiation of ECA biosynthesis, (ii) increasing the synthesis of the lipid carrier undecaprenyl phosphate (Und-P), (iii) diverting Und-P to PG synthesis or (iv) promoting Und-P recycling. The results argue that the buildup of ECA-lipid II sequesters part of the pool of Und-P, which, in turn, adversely affects PG synthesis. The data strongly suggest there is competition for a common pool of Und-P, whose proper distribution to alternate metabolic pathways is required to maintain normal cell shape in E. coli.
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Affiliation(s)
- Matthew A Jorgenson
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Suresh Kannan
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Mary E Laubacher
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
| | - Kevin D Young
- Department of Microbiology and Immunology, University of Arkansas for Medical Sciences, Little Rock, AR, 72205, USA
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Draft Whole-Genome Sequence of Serratia marcescens Strain RM66262, Isolated from a Patient with a Urinary Tract Infection. GENOME ANNOUNCEMENTS 2015; 3:3/6/e01423-15. [PMID: 26634764 PMCID: PMC4669405 DOI: 10.1128/genomea.01423-15] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Serratia marcescens strains are ubiquitous bacteria isolated from environmental niches and also constitute emergent nosocomial opportunistic pathogens. Here, we report on the draft genome sequence of S. marcescens strain RM66262, which was isolated from a patient with urinary tract infection in the Bacteriology Service of the Rosario National University, Rosario, Argentina.
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Liu L, Zha J, DiGiandomenico A, McAllister D, Stover CK, Wang Q, Boons GJ. Synthetic Enterobacterial Common Antigen (ECA) for the Development of a Universal Immunotherapy for Drug-Resistant Enterobacteriaceae. Angew Chem Int Ed Engl 2015; 54:10953-7. [PMID: 26216389 PMCID: PMC4664081 DOI: 10.1002/anie.201505420] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2015] [Indexed: 11/06/2022]
Abstract
All Enterobacteriaceae express a polysaccharide known as enterobacterial common antigen (ECA), which is an attractive target for the development of universally acting immunotherapies. The first chemical synthesis of ECA-derived oligosaccharides for the development of such therapies is described. A number of synthetic challenges had to be addressed, including the development of concise synthetic procedures for unusual monosaccharides, the selection of appropriate orthogonal protecting groups, the development of stereoselective glycosylation methods, appropriate timing for the introduction of the carboxylic acid groups on the ManpNAcA moieties, and the selection of appropriate conditions for the reduction of multiple azido moieties. The synthetic compounds were employed to uncover immunodominant moieties of ECA. Furthermore, a monoclonal antibody (mAb) was developed that binds to ECA and can selectively recognize a wide range of Enterobacteriaceae species.
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Affiliation(s)
- Lin Liu
- Complex Carbohydrate Research Center, The University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA)
| | - Jingying Zha
- Department of Infectious Diseases, MedImmune, LLC, Gaithersburg, MD 20878 (USA)
| | | | | | - C Kendall Stover
- Department of Infectious Diseases, MedImmune, LLC, Gaithersburg, MD 20878 (USA)
| | - Qun Wang
- Department of Infectious Diseases, MedImmune, LLC, Gaithersburg, MD 20878 (USA).
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, The University of Georgia, 315 Riverbend Road, Athens, GA 30602 (USA).
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Liu L, Zha J, DiGiandomenico A, McAllister D, Stover CK, Wang Q, Boons GJ. Synthetic Enterobacterial Common Antigen (ECA) for the Development of a Universal Immunotherapy for Drug-ResistantEnterobacteriaceae. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201505420] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Ancona V, Chatnaparat T, Zhao Y. Conserved aspartate and lysine residues of RcsB are required for amylovoran biosynthesis, virulence, and DNA binding in Erwinia amylovora. Mol Genet Genomics 2015; 290:1265-76. [PMID: 25577258 DOI: 10.1007/s00438-015-0988-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Accepted: 01/05/2015] [Indexed: 11/25/2022]
Abstract
In Erwinia amylovora, the Rcs phosphorelay system is essential for amylovoran production and virulence. To further understand the role of conserved aspartate residue (D56) in the phosphor receiver (PR) domain and lysine (K180) residue in the function domain of RcsB, amino acid substitutions of RcsB mutant alleles were generated by site-directed mutagenesis and complementation of various rcs mutants were performed. A D56E substitution of RcsB, which mimics the phosphorylation state of RcsB, complemented the rcsB mutant, resulting in increased amylovoran production and gene expression, reduced swarming motility, and restored pathogenicity. In contrast, D56N and K180A or K180Q substitutions of RcsB did not complement the rcsB mutant. Electrophoresis mobility shift assays showed that D56E, but not D56N, K180Q and K180A substitutions of RcsB bound to promoters of amsG and flhD, indicating that both D56 and K180 are required for DNA binding. Interestingly, the RcsBD56E allele could also complement rcsAB, rcsBC and rcsABCD mutants with restored virulence and increased amylovoran production, indicating that RcsB phosphorylation is essential for virulence of E. amylovora. In addition, mutations of T904 and A905, but not phosphorylation mimic mutation of D876 in the PR domain of RcsC, constitutively activate the Rcs system, suggesting that phosphor transfer is required for activating the Rcs system and indicating both A905 and T904 are required for the phosphatase activity of RcsC. Our results demonstrated that RcsB phosphorylation and dephosphorylation, phosphor transfer from RcsC are essential for the function of the Rcs system, and also suggested that constitutive activation of the Rcs system could reduce the fitness of E. amylovora.
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Affiliation(s)
- Veronica Ancona
- Department of Crop Sciences, University of Illinois at Urbana-Champaign, 1201 W. Gregory Dr, Urbana, IL, 61801, USA
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Noszczyńska M, Kasperkiewicz K, Duda KA, Podhorodecka J, Rabsztyn K, Gwizdała K, Świerzko AS, Radziejewska-Lebrecht J, Holst O, Skurnik M. Serological characterization of the enterobacterial common antigen substitution of the lipopolysaccharide of Yersinia enterocolitica O : 3. Microbiology (Reading) 2015; 161:219-227. [DOI: 10.1099/mic.0.083493-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Magdalena Noszczyńska
- Department of Microbiology, University of Silesia, Jagiellońska 28, PL- 40-032 Katowice, Poland
| | - Katarzyna Kasperkiewicz
- Department of Microbiology, University of Silesia, Jagiellońska 28, PL- 40-032 Katowice, Poland
| | - Katarzyna Anna Duda
- Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany
| | - Joanna Podhorodecka
- Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany
- Department of Microbiology, University of Silesia, Jagiellońska 28, PL- 40-032 Katowice, Poland
| | - Kamila Rabsztyn
- Department of Microbiology, University of Silesia, Jagiellońska 28, PL- 40-032 Katowice, Poland
| | - Karolina Gwizdała
- Department of Microbiology, University of Silesia, Jagiellońska 28, PL- 40-032 Katowice, Poland
| | - Anna Stanisława Świerzko
- Department of Immunobiology of Infections, Institute of Medical Biology, PAS, Lodowa 106, PL- 93-232 Łódź, Poland
| | | | - Otto Holst
- Division of Structural Biochemistry, Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Borstel, Germany
| | - Mikael Skurnik
- Helsinki University Central Hospital Laboratory Diagnostics, FIN-00270 Helsinki, Finland
- Department of Bacteriology and Immunology, Haartman Institute, and Research Programs Unit, Immunobiology, University of Helsinki, FIN-00014, Helsinki, Finland
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Ma XJ, Yang HF, Liu YY, Mei Q, Ye Y, Li HR, Cheng J, Li JB. ACT-10, a novel plasmid-encoded class C β-lactamase in a Serratia marcescens isolate from China. Diagn Microbiol Infect Dis 2014; 80:343-4. [PMID: 25312010 DOI: 10.1016/j.diagmicrobio.2014.09.020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 09/14/2014] [Accepted: 09/22/2014] [Indexed: 10/24/2022]
Affiliation(s)
- Xue-Jiao Ma
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Hai-Fei Yang
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Yan-Yan Liu
- Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Anhui Center for Surveillance of Bacterial Resistance, Hefei, China
| | - Qing Mei
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China
| | - Ying Ye
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China; Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Anhui Center for Surveillance of Bacterial Resistance, Hefei, China
| | - Hong-ru Li
- Department of Clinical Medicine, Xiangya School of Medicine, Central South University, Changsha, China
| | - Jun Cheng
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China; Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Anhui Center for Surveillance of Bacterial Resistance, Hefei, China.
| | - Jia-Bin Li
- Department of Infectious Disease, the First Affiliated Hospital of Anhui Medical University, Hefei, China; Institute of Bacterium Resistance, Anhui Medical University, Hefei, China; Anhui Center for Surveillance of Bacterial Resistance, Hefei, China; Department of Infectious Disease, Chaohu Hospital of Anhui Medical University, Hefei, China.
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38
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Biofilms, flagella, and mechanosensing of surfaces by bacteria. Trends Microbiol 2014; 22:517-27. [DOI: 10.1016/j.tim.2014.05.002] [Citation(s) in RCA: 251] [Impact Index Per Article: 25.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2014] [Revised: 05/06/2014] [Accepted: 05/08/2014] [Indexed: 11/18/2022]
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Serratia marcescens ShlA pore-forming toxin is responsible for early induction of autophagy in host cells and is transcriptionally regulated by RcsB. Infect Immun 2014; 82:3542-54. [PMID: 24914224 DOI: 10.1128/iai.01682-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Serratia marcescens is a Gram-negative bacterium that thrives in a wide variety of ambient niches and interacts with an ample range of hosts. As an opportunistic human pathogen, it has increased its clinical incidence in recent years, being responsible for life-threatening nosocomial infections. S. marcescens produces numerous exoproteins with toxic effects, including the ShlA pore-forming toxin, which has been catalogued as its most potent cytotoxin. However, the regulatory mechanisms that govern ShlA expression, as well as its action toward the host, have remained unclear. We have shown that S. marcescens elicits an autophagic response in host nonphagocytic cells. In this work, we determine that the expression of ShlA is responsible for the autophagic response that is promoted prior to bacterial internalization in epithelial cells. We show that a strain unable to express ShlA is no longer able to induce this autophagic mechanism, while heterologous expression of ShlA/ShlB suffices to confer on noninvasive Escherichia coli the capacity to trigger autophagy. We also demonstrate that shlBA harbors a binding motif for the RcsB regulator in its promoter region. RcsB-dependent control of shlBA constitutes a feed-forward regulatory mechanism that allows interplay with flagellar-biogenesis regulation. At the top of the circuit, activated RcsB downregulates expression of flagella by binding to the flhDC promoter region, preventing FliA-activated transcription of shlBA. Simultaneously, RcsB interaction within the shlBA promoter represses ShlA expression. This circuit offers multiple access points to fine-tune ShlA production. These findings also strengthen the case for an RcsB role in orchestrating the expression of Serratia virulence factors.
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Paunova-Krasteva TS, Pavlova VA, De Castro C, Ivanova RM, Molinaro A, Nikolova EB, Stoitsova SR. Cyclic enterobacterial common antigens from Escherichia coli O157 as microbe-associated molecular patterns. Can J Microbiol 2014; 60:173-6. [PMID: 24588391 DOI: 10.1139/cjm-2013-0697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In a previous study, we described 2 forms of cyclic enterobacterial common antigen (ECACYC), a tetramer and a pentamer, from Escherichia coli O157. ECACYC is present in several representatives of the Enterobacteriaceae. To date, functional studies on ECACYC are sparse. Cyclic oligosaccharides in other bacteria, like the cyclic β-glucans in Rhizobiaceae, represent microbe-associated molecular patterns involved in host-bacteria interaction. This observation determined the aim of the present study: to test whether the tetrameric and pentameric ECACYC from E. coli O157 can be recognised by host humoral and cellular mechanisms. ELISA tests designed to compare the 2 ECACYC with the O157 lipopolysaccharide showed that both ECACYC were not recognised by polyclonal anti-O157 serum but were good ligands for mannan-binding lectin. The lectin had a higher affinity for the tetramer than the pentamer. ECACYC deposited more C3b than did the lipopolysaccharide. To examine the interactions with human circulating neutrophils, the antigens were loaded onto fluorescent latex beads and applied in a phagocytosis experiment. Spheres coated with the 2 ECACYC occasionally adhered to phagocyte surfaces but, unlike O157-loaded spheres, failed to induce free-radical release. The results show that the 2 ECACYC represent microbe-associated molecular patterns recognised by host humoral non-self-recognition mechanisms.
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Affiliation(s)
- Tsvetelina S Paunova-Krasteva
- a The Stephan Angeloff Institute of Microbiology, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, Block 26, Sofia 1113, Bulgaria
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Ishii K, Adachi T, Hamamoto H, Sekimizu K. Serratia marcescens suppresses host cellular immunity via the production of an adhesion-inhibitory factor against immunosurveillance cells. J Biol Chem 2014; 289:5876-88. [PMID: 24398686 DOI: 10.1074/jbc.m113.544536] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Injection of a culture supernatant of Serratia marcescens into the bloodstream of the silkworm Bombyx mori increased the number of freely circulating immunosurveillance cells (hemocytes). Using a bioassay with live silkworms, serralysin metalloprotease was purified from the culture supernatant and identified as the factor responsible for this activity. Serralysin inhibited the in vitro attachment of both silkworm hemocytes and murine peritoneal macrophages. Incubation of silkworm hemocytes or murine macrophages with serralysin resulted in degradation of the cellular immune factor BmSPH-1 or calreticulin, respectively. Furthermore, serralysin suppressed in vitro phagocytosis of bacteria by hemocytes and in vivo bacterial clearance in silkworms. Disruption of the ser gene in S. marcescens attenuated its host killing ability in silkworms and mice. These findings suggest that serralysin metalloprotease secreted by S. marcescens suppresses cellular immunity by decreasing the adhesive properties of immunosurveillance cells, thereby contributing to bacterial pathogenesis.
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Affiliation(s)
- Kenichi Ishii
- From the Laboratory of Microbiology, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan
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42
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Gozdziewicz TK, Lugowski C, Lukasiewicz J. First evidence for a covalent linkage between enterobacterial common antigen and lipopolysaccharide in Shigella sonnei phase II ECALPS. J Biol Chem 2013; 289:2745-54. [PMID: 24324266 DOI: 10.1074/jbc.m113.512749] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Enterobacterial common antigen (ECA) is expressed by Gram-negative bacteria belonging to Enterobacteriaceae, including emerging drug-resistant pathogens such as Escherichia coli, Klebsiella pneumoniae, and Proteus spp. Recent studies have indicated the importance of ECA for cell envelope integrity, flagellum expression, and resistance of enteric bacteria to acetic acid and bile salts. ECA, a heteropolysaccharide built from the trisaccharide repeating unit, →3)-α-D-Fucp4NAc-(1→4)-β-D-ManpNAcA-(1→4)-α-D-GlcpNAc-(1→, occurs as a cyclic form (ECA(CYC)), a phosphatidylglycerol (PG)-linked form (ECA(PG)), and an endotoxin/lipopolysaccharide (LPS)-associated form (ECA(LPS)). Since the discovery of ECA in 1962, the structures of ECA(PG) and ECA(CYC) have been completely elucidated. However, no direct evidence has been presented to support a covalent linkage between ECA and LPS; only serological indications of co-association have been reported. This is paradoxical, given that ECA was first identified based on the capacity of immunogenic ECA(LPS) to elicit antibodies cross-reactive with enterobacteria. Using a simple isolation protocol supported by serological tracking of ECA epitopes and NMR spectroscopy and mass spectrometry, we have succeeded in the first detection, isolation, and complete structural analysis of poly- and oligosaccharides of Shigella sonnei phase II ECA(LPS). ECA(LPS) consists of the core oligosaccharide substituted with one to four repeating units of ECA at the position occupied by the O-antigen in the case of smooth S. sonnei phase I. These data represent the first structural evidence for the existence of ECA(LPS) in the half-century since it was first discovered and provide insights that could prove helpful in further structural analyses and screening of ECA(LPS) among Enterobacteriaceae species.
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Affiliation(s)
- Tomasz K Gozdziewicz
- From the Department of Immunochemistry, Ludwik Hirszfeld Institute of Immunology and Experimental Therapy, Polish Academy of Sciences, R. Weigla 12, PL-53-114 Wroclaw, Poland and
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Bowden SD, Hale N, Chung JCS, Hodgkinson JT, Spring DR, Welch M. Surface swarming motility by Pectobacterium atrosepticum is a latent phenotype that requires O antigen and is regulated by quorum sensing. Microbiology (Reading) 2013; 159:2375-2385. [DOI: 10.1099/mic.0.070748-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Steven D. Bowden
- Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Nicola Hale
- Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1QW, UK
| | - Jade C. S. Chung
- Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1QW, UK
| | | | - David R. Spring
- Department of Chemistry, Lensfield Road, Cambridge, CB2 1EW, UK
| | - Martin Welch
- Department of Biochemistry, Tennis Court Road, Cambridge, CB2 1QW, UK
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Fregolino E, Ivanova R, Lanzetta R, Molinaro A, Parrilli M, Paunova-Krasteva T, Stoitsova SR, De Castro C. Occurrence and structure of cyclic Enterobacterial Common Antigen in Escherichia coli O157:H⁻. Carbohydr Res 2012; 363:29-32. [PMID: 23103511 DOI: 10.1016/j.carres.2012.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Revised: 09/18/2012] [Accepted: 09/20/2012] [Indexed: 10/27/2022]
Abstract
Two cyclic forms of the Enterobacterial Common Antigen were isolated from Escherichia coli O157:H(-). These antigenic determinants were purified from the biomass through extensive chemical, enzymatic and chromatographic procedures whereas MALDI MS spectrometry indicated their cyclic nature with a polymerization degree of 4 or 5. The two species, denoted as ECA(CYC-4) and ECA(CYC-5), were assigned by NMR and showed no further substitution with other appendages such as acetyl groups as usually described for similar cyclic antigens from other Enterobacteriaceae.
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Affiliation(s)
- Eleonora Fregolino
- Università di Napoli Federico II, Dipartimento di Scienze Chimiche, Complesso Universitario Monte Sant'Angelo, Via Cintia 4, 80126 Napoli, Italy
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45
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Wang LY, Lin SS, Hung TH, Li TK, Lin NC, Shen TL. Multiple domains of the tobacco mosaic virus p126 protein can independently suppress local and systemic RNA silencing. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2012; 25:6-17. [PMID: 22324815 DOI: 10.1094/mpmi-08-11-0207] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Small RNA-mediated RNA silencing is a widespread antiviral mechanism in plants and other organisms. Many viruses encode suppressors of RNA silencing for counter-defense. The p126 protein encoded by Tobacco mosaic virus (TMV) has been reported to be a suppressor of RNA silencing but the mechanism of its function remains unclear. This protein is unique among the known plant viral silencing suppressors because of its large size and multiple domains. Here, we report that the methyltransferase, helicase, and nonconserved region II (NONII) of p126 each has silencing-suppressor function. The silencing-suppression activities of methyltransferase and helicase can be uncoupled from their enzyme activities. Specific amino acids in NONII previously shown to be crucial for viral accumulation and symptom development are also crucial for silencing suppression. These results suggest that some viral proteins have evolved to possess modular structural domains that can independently interfere with host silencing, and that this may be an effective mechanism of increasing the robustness of a virus.
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Affiliation(s)
- Li-Ya Wang
- Department of Plant Pathology and Microbiology, College of Bioresources and Agriculture, National Taiwan University, Taipei, Taiwan
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46
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Biogenesis of outer membrane vesicles in Serratia marcescens is thermoregulated and can be induced by activation of the Rcs phosphorelay system. J Bacteriol 2012; 194:3241-9. [PMID: 22493021 DOI: 10.1128/jb.00016-12] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Outer membrane vesicles (OMVs) have been identified in a wide range of bacteria, yet little is known of their biogenesis. It has been proposed that OMVs can act as long-range toxin delivery vectors and as a novel stress response. We have found that the formation of OMVs in the gram-negative opportunistic pathogen Serratia marcescens is thermoregulated, with a significant amount of OMVs produced at 22 or 30°C and negligible quantities formed at 37°C under laboratory conditions. Inactivation of the synthesis of the enterobacterial common antigen (ECA) resulted in a hypervesiculation phenotype, supporting the hypothesis that OMVs are produced in response to stress. We demonstrate that the phenotype can be reversed to wild-type (WT) levels upon the loss of the Rcs phosphorelay response regulator RcsB, but not RcsA, suggesting a role for the Rcs phosphorelay in the production of OMVs. MS fingerprinting of the OMVs provided evidence of cargo selection within wild-type cells, suggesting a possible role for Serratia OMVs in toxin delivery. In addition, OMV-associated cargo proved toxic upon injection into the haemocoel of Galleria mellonella larvae. These experiments demonstrate that OMVs are the result of a regulated process in Serratia and suggest that OMVs could play a role in virulence.
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47
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Patrick JE, Kearns DB. Swarming motility and the control of master regulators of flagellar biosynthesis. Mol Microbiol 2011; 83:14-23. [PMID: 22092493 DOI: 10.1111/j.1365-2958.2011.07917.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Swarming motility is the movement of bacteria over a solid surface powered by rotating flagella. The expression of flagellar biosynthesis genes is governed by species-specific master regulator transcription factors. Mutations that reduce or enhance master regulator activity have a commensurate effect on swarming motility. Here we review what is known about the proteins that modulate swarming motility and appear to act upstream of the master flagellar regulators in diverse swarming bacteria. We hypothesize that environmental control of the master regulators is important to the swarming phenotype perhaps at the level of controlling flagellar number.
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Affiliation(s)
- Joyce E Patrick
- Indiana University, Department of Biology, 1001 East Third Street, Bloomington, IN 47405, USA
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