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New approaches and techniques for bacterial cell wall analysis. Curr Opin Microbiol 2021; 60:88-95. [PMID: 33631455 DOI: 10.1016/j.mib.2021.01.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/22/2021] [Accepted: 01/22/2021] [Indexed: 12/17/2022]
Abstract
Peptidoglycan (PG) has remained for decades in the spotlight of the never-ending battle against pathogenic bacteria as this essential bacterial structure is one of the most successful targets for antibiotics. Most of our current understanding about the composition, architecture, and dynamics of the PG relies on techniques which have experienced great technological and methodological improvements in the past years. Here we summarize recent advances in these methods with the intention to furnish a valuable resource for both PG experts and newcomers.
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Mursalin MH, Coburn PS, Miller FC, Livingston ET, Astley R, Callegan MC. Innate Immune Interference Attenuates Inflammation In Bacillus Endophthalmitis. Invest Ophthalmol Vis Sci 2020; 61:17. [PMID: 33180117 PMCID: PMC7671874 DOI: 10.1167/iovs.61.13.17] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Accepted: 10/20/2020] [Indexed: 02/07/2023] Open
Abstract
Purpose To explore the consequences of innate interference on intraocular inflammatory responses during Bacillus endophthalmitis. Methods Bacillus endophthalmitis was induced in mice. Innate immune pathway activation was interfered by injecting S layer protein-deficient (∆slpA) B. thuringiensis or by treating wild-type (WT)-infected mice with a TLR2/4 inhibitor (WT+OxPAPC). At 10 hours postinfection, eyes were harvested and RNA was purified. A NanoString murine inflammation panel was used to compare gene expression in WT-infected, WT+OxPAPC, ∆slpA-infected, and uninfected eyes. Results In WT-infected eyes, 56% of genes were significantly upregulated compared to uninfected controls. Compared to WT-infected eyes, the expression of 27% and 50% of genes were significantly reduced in WT+OxPAPC and ∆slpA-infected eyes, respectively. Expression of 61 genes that were upregulated in WT-infected eyes was decreased in WT+OxPAPC and ∆slpA-infected eyes. Innate interference resulted in blunted expression of complement factors (C3, Cfb, and C6) and several innate pathway genes (TLRs 2, 4, 6, and 8, MyD88, Nod2, Nlrp3, NF-κB, STAT3, RelA, RelB, and Ptgs2). Innate interference also reduced the expression of several inflammatory cytokines (CSF2, CSF3, IL-6, IL-1β, IL-1α, TNFα, IL-23α, TGFβ1, and IL-12β) and chemokines (CCL2, CCL3, and CXCLs 1, 2, 3, 5, 9, and 10). All of the aforementioned genes were significantly upregulated in WT-infected eyes. Conclusions These results suggest that interfering with innate activation significantly reduced the intraocular inflammatory response in Bacillus endophthalmitis. This positive clinical outcome could be a strategy for anti-inflammatory therapy of an infection typically refractory to corticosteroid treatment.
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Affiliation(s)
- Md Huzzatul Mursalin
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Phillip S. Coburn
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Frederick C. Miller
- Department of Cell Biology and Department of Family and Preventive Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Erin T. Livingston
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Roger Astley
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Michelle C. Callegan
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
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Ellison AJ, Dempwolff F, Kearns DB, Raines RT. Role for Cell-Surface Collagen of Streptococcus pyogenes in Infections. ACS Infect Dis 2020; 6:1836-1843. [PMID: 32413256 DOI: 10.1021/acsinfecdis.0c00073] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Group A Streptococcus (GAS) displays cell-surface proteins that resemble human collagen. We find that a fluorophore-labeled collagen mimetic peptide (CMP) labels GAS cells but not Escherichia coli or Bacillus subtilis cells, which lack such proteins. The CMP likely engages in a heterotrimeric helix with endogenous collagen, as the nonnatural d enantiomer of the CMP does not label GAS cells. To identify a molecular target, we used reverse genetics to "knock-in" the GAS genes that encode two proteins with collagen-like domains, Scl1 and Scl2, into B. subtilis. The fluorescent CMP labels the cells of these B. subtilis strains. Moreover, these strains bind tightly to a surface of mammalian collagen. These data are consistent with streptococcal collagen forming triple helices with damaged collagen in a wound bed and thus have implications for microbial virulence.
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Affiliation(s)
| | - Felix Dempwolff
- Department of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - Daniel B. Kearns
- Department of Biology, Indiana University, Bloomington, Indiana 47405, United States
| | - Ronald T. Raines
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Chung S, Darwin AJ. The C-terminus of substrates is critical but not sufficient for their degradation by the Pseudomonas aeruginosa CtpA protease. J Bacteriol 2020; 202:JB.00174-20. [PMID: 32482720 PMCID: PMC8404705 DOI: 10.1128/jb.00174-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 05/26/2020] [Indexed: 02/08/2023] Open
Abstract
Bacterial carboxyl-terminal processing proteases (CTPs) are widely conserved and have been linked to important processes including signal transduction, cell wall metabolism, and virulence. However, the features that target proteins for CTP-dependent cleavage are unclear. Studies of the Escherichia coli CTP Prc suggested that it cleaves proteins with non-polar and/or structurally unconstrained C-termini, but it is not clear if this applies broadly. Pseudomonas aeruginosa has a divergent CTP, CtpA, which is required for virulence. CtpA works in complex with the outer membrane lipoprotein LbcA to degrade cell wall hydrolases. Here, we investigated if the C-termini of two non-homologous CtpA substrates are important for their degradation. We determined that these substrates have extended C-termini, compared to their closest E. coli homologs. Removing seven amino acids from these extensions was sufficient to reduce their degradation by CtpA both in vivo and in vitro Degradation of one truncated substrate was restored by adding the C-terminus from the other, but not by adding an unrelated sequence. However, modification of the C-terminus of non-substrates, by adding the C-terminal amino acids from a substrate, did not cause their degradation by CtpA. Therefore, the C-termini of CtpA substrates are required but not sufficient for their efficient degradation. Although C-terminal truncated substrates were protected from degradation, they still associated with the LbcA•CtpA complex in vivo Therefore, degradation of a protein by CtpA requires a C-terminal-independent interaction with the LbcA•CtpA complex, followed by C-terminal-dependent degradation, perhaps because CtpA normally initiates cleavage at a C-terminal site.IMPORTANCE Carboxyl-terminal processing proteases (CTPs) are found in all three domains of life, but exactly how they work is poorly understood, including how they recognize substrates. Bacterial CTPs have been associated with virulence, including CtpA of Pseudomonas aeruginosa, which works in complex with the outer membrane lipoprotein LbcA to degrade potentially dangerous peptidoglycan hydrolases. We report an important advance by revealing that efficient degradation by CtpA requires at least two separable phenomena, and that one of them depends on information encoded in the substrate C-terminus. A C-terminal-independent association with the LbcA•CtpA complex is followed by C-terminal-dependent cleavage by CtpA. Increased understanding of how CTPs target proteins is significant, due to their links to virulence, peptidoglycan remodeling, and other important processes.
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Affiliation(s)
- Sammi Chung
- Department of Microbiology, New York University School of Medicine, New York, NY
| | - Andrew J Darwin
- Department of Microbiology, New York University School of Medicine, New York, NY
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Mursalin MH, Livingston ET, Callegan MC. The cereus matter of Bacillus endophthalmitis. Exp Eye Res 2020; 193:107959. [PMID: 32032628 PMCID: PMC7113113 DOI: 10.1016/j.exer.2020.107959] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/06/2020] [Accepted: 02/03/2020] [Indexed: 02/06/2023]
Abstract
Bacillus cereus (B. cereus) endophthalmitis is a devastating intraocular infection primarily associated with post-traumatic injuries. The majority of these infections result in substantial vision loss, if not loss of the eye itself, within 12-48 h. Multifactorial mechanisms that lead to the innate intraocular inflammatory response during this disease include the combination of robust bacterial replication, migration of the organism throughout the eye, and toxin production by the organism. Therefore, the window of therapeutic intervention in B. cereus endophthalmitis is quite narrow compared to that of other pathogens which cause this disease. Understanding the interaction of bacterial and host factors is critical in understanding the disease and formulating more rational therapeutics for salvaging vision. In this review, we will discuss clinical and research findings related to B. cereus endophthalmitis in terms of the organism's virulence and inflammogenic potential, and strategies for improving of current therapeutic regimens for this blinding disease.
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Affiliation(s)
- Md Huzzatul Mursalin
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Erin T Livingston
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michelle C Callegan
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, OK, USA; Oklahoma Center for Neuroscience, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK, USA.
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Mursalin MH, Coburn PS, Livingston E, Miller FC, Astley R, Flores-Mireles AL, Callegan MC. Bacillus S-Layer-Mediated Innate Interactions During Endophthalmitis. Front Immunol 2020; 11:215. [PMID: 32117322 PMCID: PMC7028758 DOI: 10.3389/fimmu.2020.00215] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 01/27/2020] [Indexed: 12/14/2022] Open
Abstract
Bacillus endophthalmitis is a severe intraocular infection. Hallmarks of Bacillus endophthalmitis include robust inflammation and rapid loss of vision. We reported that the absence of Bacillus surface layer protein (SLP) significantly blunted endophthalmitis severity. Here, we further investigated SLP in the context of Bacillus-retinal cell interactions and innate immune pathways to explore the mechanisms by which SLP contributes to intraocular inflammation. We compared phenotypes of Wild-type (WT) and SLP deficient (ΔslpA) Bacillus thuringiensis by analyzing bacterial adherence to and phagocytosis by human retinal Muller cells and phagocytosis by mouse neutrophils. Innate immune receptor activation by the Bacillus envelope and purified SLP was analyzed using TLR2/4 reporter cell lines. A synthetic TLR2/4 inhibitor was used as a control for this receptor activation. To induce endophthalmitis, mouse eyes were injected intravitreally with 100 CFU WT or ΔslpA B. thuringiensis. A group of WT infected mice was treated intravitreally with a TLR2/4 inhibitor at 4 h postinfection. At 10 h postinfection, infected eyes were analyzed for viable bacteria, inflammation, and retinal function. We observed that B. thuringiensis SLPs contributed to retinal Muller cell adherence, and protected this pathogen from Muller cell- and neutrophil-mediated phagocytosis. We found that B. thuringiensis envelope activated TLR2 and, surprisingly, TLR4, suggesting the presence of a surface-associated TLR4 agonist in Bacillus. Further investigation showed that purified SLP from B. thuringiensis activated TLR4, as well as TLR2 in vitro. Growth of WT B. thuringiensis was significantly higher and caused greater inflammation in untreated eyes than in eyes treated with the TLR2/4 inhibitor. Retinal function analysis also showed greater retention of A-wave and B-wave function in infected eyes treated with the TLR2/4 inhibitor. The TLR2/4 inhibitor was not antibacterial in vitro, and did not cause inflammation when injected into uninfected eyes. Taken together, these results suggest a potential role for Bacillus SLP in host-bacterial interactions, as well as in endophthalmitis pathogenesis via TLR2- and TLR4-mediated pathways.
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Affiliation(s)
- Md Huzzatul Mursalin
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Phillip S. Coburn
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Dean McGee Eye Institute, Oklahoma City, OK, United States
| | - Erin Livingston
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Frederick C. Miller
- Department of Cell Biology and Department of Family and Preventive Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
| | - Roger Astley
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Dean McGee Eye Institute, Oklahoma City, OK, United States
| | - Ana L. Flores-Mireles
- Department of Biological Sciences, University of Notre Dame, South Bend, IN, United States
| | - Michelle C. Callegan
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States
- Dean McGee Eye Institute, Oklahoma City, OK, United States
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Rehman T, Yin L, Latif MB, Chen J, Wang K, Geng Y, Huang X, Abaidullah M, Guo H, Ouyang P. Adhesive mechanism of different Salmonella fimbrial adhesins. Microb Pathog 2019; 137:103748. [PMID: 31521802 DOI: 10.1016/j.micpath.2019.103748] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Revised: 09/10/2019] [Accepted: 09/11/2019] [Indexed: 02/01/2023]
Abstract
Salmonellosis is a serious threat to human and animal health. Salmonella adhesion to the host cell is an initial and most crucial step in the pathogenesis of salmonellosis. Many factors are involved in the adhesion process of Salmonella infection. Fimbriae are one of the most important factors in the adhesion of Salmonella. The Salmonella fimbriae are assembled in three types of assembly pathways: chaperon-usher, nucleation-precipitation, and type IV fimbriae. These assembly pathways lead to multiple types of fimbriae. Salmonella fimbriae bind to host cell receptors to initiate adhesion. So far, many receptors have been identified, such as Toll-like receptors. However, several receptors that may be involved in the adhesive mechanism of Salmonella fimbriae are still un-identified. This review aimed to summarize the types of Salmonella fimbriae produced by different assembly pathways and their role in adhesion. It also enlisted previously discovered receptors involved in adhesion. This review might help readers to develop a comprehensive understanding of Salmonella fimbriae, their role in adhesion, and recently developed strategies to counter Salmonella infection.
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Affiliation(s)
- Tayyab Rehman
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Lizi Yin
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Muhammad Bilal Latif
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, 44195, Ohio, USA.
| | - Jiehao Chen
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Kaiyu Wang
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Yi Geng
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Xiaoli Huang
- Department of Aquaculture, College of Animal Science and Technology, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Muhammad Abaidullah
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Hongrui Guo
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
| | - Ping Ouyang
- Department of Basic Veterinary, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, 611130, Sichuan, China.
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Mursalin MH, Coburn PS, Livingston E, Miller FC, Astley R, Fouet A, Callegan MC. S-layer Impacts the Virulence of Bacillus in Endophthalmitis. Invest Ophthalmol Vis Sci 2019; 60:3727-3739. [PMID: 31479113 PMCID: PMC6719748 DOI: 10.1167/iovs.19-27453] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2019] [Accepted: 07/19/2019] [Indexed: 02/07/2023] Open
Abstract
Purpose Bacillus causes a sight-threating infection of the posterior segment of the eye. The robust intraocular inflammatory response in this disease is likely activated via host innate receptor interactions with components of the Bacillus cell envelope. S-layer proteins (SLPs) of some Gram-positive pathogens contribute to the pathogenesis of certain infections. The potential contributions of SLPs in eye infection pathogenesis have not been considered. Here, we explored the role of a Bacillus SLP (SlpA) in endophthalmitis pathogenesis. Methods The phenotypes and infectivity of wild-type (WT) and S-layer deficient (ΔslpA) Bacillus thuringiensis were compared. Experimental endophthalmitis was induced in C57BL/6J mice by intravitreally injecting 100-CFU WT or ΔslpA B. thuringiensis. Infected eyes were analyzed by bacterial counts, retinal function analysis, histology, and inflammatory cell influx. SLP-induced inflammation was also analyzed in vitro. Muller cells (MIO-M1) were treated with purified SLP. Nuclear factor-κB (NF-κB) DNA binding was measured by ELISA and expression of proinflammatory mediators from Muller cells was measured by RT-qPCR. Results Tested phenotypes of WT and ΔslpA B. thuringiensis were similar, with the exception of absence of the S-layer in the ΔslpA mutant. Intraocular growth of WT and ΔslpA B. thuringiensis was also similar. However, eyes infected with the ΔslpA mutant had significantly reduced inflammatory cell influx, less inflammatory damage to the eyes, and significant retention of retinal function compared with WT-infected eyes. SLP was also a potent stimulator of the NF-κB pathway and induced the expression of proinflammatory mediators (IL6, TNFα, CCL2, and CXCL-1) in human retinal Muller cells. Conclusions Taken together, our results suggest that SlpA contributes to the pathogenesis of Bacillus endophthalmitis, potentially by triggering innate inflammatory pathways in the retina.
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Affiliation(s)
- Md Huzzatul Mursalin
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Phillip S. Coburn
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Erin Livingston
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Frederick C. Miller
- Department of Cell Biology and Department of Family and Preventive Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Roger Astley
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
| | - Agnès Fouet
- Institut Cochin INSERM U1016, Paris, France
- CNRS 8104, Paris, France
- University Paris Descartes, Paris, France
| | - Michelle C. Callegan
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
- Department of Ophthalmology, Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Dean McGee Eye Institute, Oklahoma City, Oklahoma, United States
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
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Enzymes and Mechanisms Employed by Tailed Bacteriophages to Breach the Bacterial Cell Barriers. Viruses 2018; 10:v10080396. [PMID: 30060520 PMCID: PMC6116005 DOI: 10.3390/v10080396] [Citation(s) in RCA: 97] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Revised: 07/23/2018] [Accepted: 07/26/2018] [Indexed: 01/07/2023] Open
Abstract
Monoderm bacteria possess a cell envelope made of a cytoplasmic membrane and a cell wall, whereas diderm bacteria have and extra lipid layer, the outer membrane, covering the cell wall. Both cell types can also produce extracellular protective coats composed of polymeric substances like, for example, polysaccharidic capsules. Many of these structures form a tight physical barrier impenetrable by phage virus particles. Tailed phages evolved strategies/functions to overcome the different layers of the bacterial cell envelope, first to deliver the genetic material to the host cell cytoplasm for virus multiplication, and then to release the virion offspring at the end of the reproductive cycle. There is however a major difference between these two crucial steps of the phage infection cycle: virus entry cannot compromise cell viability, whereas effective virion progeny release requires host cell lysis. Here we present an overview of the viral structures, key protein players and mechanisms underlying phage DNA entry to bacteria, and then escape of the newly-formed virus particles from infected hosts. Understanding the biological context and mode of action of the phage-derived enzymes that compromise the bacterial cell envelope may provide valuable information for their application as antimicrobials.
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Dik DA, Fisher JF, Mobashery S. Cell-Wall Recycling of the Gram-Negative Bacteria and the Nexus to Antibiotic Resistance. Chem Rev 2018; 118:5952-5984. [PMID: 29847102 PMCID: PMC6855303 DOI: 10.1021/acs.chemrev.8b00277] [Citation(s) in RCA: 121] [Impact Index Per Article: 20.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The importance of the cell wall to the viability of the bacterium is underscored by the breadth of antibiotic structures that act by blocking key enzymes that are tasked with cell-wall creation, preservation, and regulation. The interplay between cell-wall integrity, and the summoning forth of resistance mechanisms to deactivate cell-wall-targeting antibiotics, involves exquisite orchestration among cell-wall synthesis and remodeling and the detection of and response to the antibiotics through modulation of gene regulation by specific effectors. Given the profound importance of antibiotics to the practice of medicine, the assertion that understanding this interplay is among the most fundamentally important questions in bacterial physiology is credible. The enigmatic regulation of the expression of the AmpC β-lactamase, a clinically significant and highly regulated resistance response of certain Gram-negative bacteria to the β-lactam antibiotics, is the exemplar of this challenge. This review gives a current perspective to this compelling, and still not fully solved, 35-year enigma.
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Affiliation(s)
- David A. Dik
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Jed F. Fisher
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Shahriar Mobashery
- Department of Chemistry and Biochemistry, McCourtney Hall, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Major Tom to Ground Control: How Lipoproteins Communicate Extracytoplasmic Stress to the Decision Center of the Cell. J Bacteriol 2017; 199:JB.00216-17. [PMID: 28674071 DOI: 10.1128/jb.00216-17] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The envelope of bacteria is a complex multilayered shield that ensures multiple essential functions, including protecting the cell from external assaults. Hence, bacterial cells have evolved intricate mechanisms called envelope stress response systems (ESRS) to monitor all kinds of perturbations affecting the integrity of their envelope and to mount an appropriate response to contain or repair the damage. In the model bacterium Escherichia coli, several ESRS are built around a two-component system, in which envelope stress triggers a phosphotransfer between a sensor protein in the inner membrane of the envelope and a response regulator in the cytoplasm. In this review, we focus on two major ESRS in E. coli, the Rcs and Cpx pathways, in which additional proteins not directly involved in the phosphotransfer modulate signal transduction. Both the Rcs and Cpx systems can be turned on by a lipoprotein anchored in the outer membrane, RcsF and NlpE, respectively, providing a molecular connection between the most exterior layer of the envelope and the ground control center in the cytoplasm. Here, we review how these two lipoproteins, which share a striking set of features while being distinct in several aspects, act as sentinels at the front line of the bacterium by sensing and transducing stress to the downstream components of the Rcs and Cpx systems.
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Gravel J, Paradis-Bleau C, Schmitzer AR. Adaptation of a bacterial membrane permeabilization assay for quantitative evaluation of benzalkonium chloride as a membrane-disrupting agent. MEDCHEMCOMM 2017; 8:1408-1413. [PMID: 30108851 PMCID: PMC6072009 DOI: 10.1039/c7md00113d] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2017] [Accepted: 04/28/2017] [Indexed: 01/31/2023]
Abstract
We describe the use of the ortho-nitrophenyl-β-galactoside (ONPG) assay developed by Lehrer et al. to which a new mathematical data treatment was applied. In this simplified assay, only one enzymatic assay is needed to provide direct evidence of the kinetics of Escherichia coli membrane permeabilization induced by different concentrations of benzalkonium chloride (BAC). Analysis of the data obtained from the revised ONPG assay with our adapted mathematical formula indicates that BAC induces permeabilization of the bacterial outer and inner membranes in a two-step process. The two effective concentration (EC50) values obtained in this study, combined with the results from an outer membrane permeabilization assay, suggest that the two steps observed in the permeabilization process are related to the two different bacterial membranes. We show that membrane permeabilization occurs very fast upon the addition of bacterial cells to the BAC solutions and demonstrate that sub-lethal concentrations of BAC disturb the integrity of the Gram-negative bacterial membranes. Overall, our work broadens our knowledge on the mode of action of BAC on bacterial cells and emphasizes that BAC, and quaternary ammonium compounds in general, should not be used at sub-lethal concentrations in order to lower the risk of bacterial tolerance and resistance to antibiotics.
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Affiliation(s)
- Julien Gravel
- Département de Chimie , Université de Montréal , CP 6128, Succ. Centre Ville , Montréal (Québec) , Canada .
| | - Catherine Paradis-Bleau
- Département de Microbiologie, Infectiologie et Immunologie , Université de Montréal , CP 6128, Succ. Centre-ville , Montréal (Québec) , Canada .
| | - Andreea R Schmitzer
- Département de Chimie , Université de Montréal , CP 6128, Succ. Centre Ville , Montréal (Québec) , Canada .
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Radeck J, Fritz G, Mascher T. The cell envelope stress response of Bacillus subtilis: from static signaling devices to dynamic regulatory network. Curr Genet 2016; 63:79-90. [PMID: 27344142 DOI: 10.1007/s00294-016-0624-0] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 11/24/2022]
Abstract
The cell envelope stress response (CESR) encompasses all regulatory events that enable a cell to protect the integrity of its envelope, an essential structure of any bacterial cell. The underlying signaling network is particularly well understood in the Gram-positive model organism Bacillus subtilis. It consists of a number of two-component systems (2CS) and extracytoplasmic function σ factors that together regulate the production of both specific resistance determinants and general mechanisms to protect the envelope against antimicrobial peptides targeting the biogenesis of the cell wall. Here, we summarize the current picture of the B. subtilis CESR network, from the initial identification of the corresponding signaling devices to unraveling their interdependence and the underlying regulatory hierarchy within the network. In the course of detailed mechanistic studies, a number of novel signaling features could be described for the 2CSs involved in mediating CESR. This includes a novel class of so-called intramembrane-sensing histidine kinases (IM-HKs), which-instead of acting as stress sensors themselves-are activated via interprotein signal transfer. Some of these IM-HKs are involved in sensing the flux of antibiotic resistance transporters, a unique mechanism of responding to extracellular antibiotic challenge.
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Affiliation(s)
- Jara Radeck
- Institute of Microbiology, Technische Universität (TU) Dresden, Dresden, Germany
| | - Georg Fritz
- LOEWE-Center for Synthetic Microbiology (SYNMIKRO), Philipps-Universität Marburg, Marburg, Germany
| | - Thorsten Mascher
- Institute of Microbiology, Technische Universität (TU) Dresden, Dresden, Germany.
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