Attachment of Enterohemorrhagic Escherichia coli to Host Cells Reduces O Antigen Chain Length at the Infection Site That Promotes Infection

Little is known about the regulation of cell wall structure of enteropathogenic bacteria within the host. Here, we report that enterohemorrhagic Escherichia coli regulates its cell wall structure during the infection process, which balances its survival in the intestinal lumen and infection of intestinal epithelial cells.

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EspZ of Enteropathogenic and Enterohemorrhagic Escherichia coli Regulates Type III Secretion System Protein Translocation

mBio ◽

10.1128/mbio.00317-12 ◽

2012 ◽

Vol 3 (5) ◽

Cited By ~ 29

Author(s):

Cedric N. Berger ◽

Valerie F. Crepin ◽

Kobi Baruch ◽

Aurelie Mousnier ◽

Ilan Rosenshine ◽

...

Keyword(s):

Escherichia Coli ◽

Type Iii Secretion ◽

Protein Translocation ◽

Type Iii Secretion System ◽

Secretion System ◽

Enterohemorrhagic Escherichia Coli ◽

Host Cells ◽

Dependent Manner ◽

Content Type ◽

Type Iii

ABSTRACTTranslocation of effector proteins via a type III secretion system (T3SS) is a widespread infection strategy among Gram-negative bacterial pathogens. Each pathogen translocates a particular set of effectors that subvert cell signaling in a way that suits its particular infection cycle. However, as effector unbalance might lead to cytotoxicity, the pathogens must employ mechanisms that regulate the intracellular effector concentration. We present evidence that the effector EspZ controls T3SS effector translocation from enteropathogenic (EPEC) and enterohemorrhagic (EHEC)Escherichia coli. Consistently, an EPECespZmutant is highly cytotoxic. Following ectopic expression, we found that EspZ inhibited the formation of actin pedestals as it blocked the translocation of Tir, as well as other effectors, including Map and EspF. Moreover, during infection EspZ inhibited effector translocation following superinfection. Importantly, while EspZ of EHEC O157:H7 had a universal “translocation stop” activity, EspZ of EPEC inhibited effector translocation from typical EPEC strains but not from EHEC O157:H7 or its progenitor, atypical EPEC O55:H7. We found that the N and C termini of EspZ, which contains two transmembrane domains, face the cytosolic leaflet of the plasma membrane at the site of bacterial attachment, while the extracellular loop of EspZ is responsible for its strain-specific activity. These results show that EPEC and EHEC acquired a sophisticated mechanism to regulate the effector translocation.IMPORTANCEEnteropathogenicEscherichia coli(EPEC) and enterohemorrhagicE. coli(EHEC) are important diarrheal pathogens responsible for significant morbidity and mortality in developing countries and the developed world, respectively. The virulence strategy of EPEC and EHEC revolves around a conserved type III secretion system (T3SS), which translocates bacterial proteins known as effectors directly into host cells. Previous studies have shown that when cells are infected in two waves with EPEC, the first wave inhibits effector translocation by the second wave in a T3SS-dependent manner, although the factor involved was not known. Importantly, we identified EspZ as the effector responsible for blocking protein translocation following a secondary EPEC infection. Interestingly, we found that while EspZ of EHEC can block protein translocation from both EPEC and EHEC strains, EPEC EspZ cannot block translocation from EHEC. These studies show that EPEC and EHEC employ a novel infection strategy to regulate T3SS translocation.

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Bacteriophage T4D receptors and the Escherichia coli cell wall structure: role of spherical particles and protein b of the cell wall in bacteriophage infection.

Journal of Bacteriology ◽

10.1128/jb.137.1.545-555.1979 ◽

1979 ◽

Vol 137 (1) ◽

pp. 545-555 ◽

Cited By ~ 9

Author(s):

J Zorzopulos ◽

L M Kozloff ◽

V Chapman ◽

S DeLong

Keyword(s):

Escherichia Coli ◽

Cell Wall ◽

Cell Wall Structure ◽

Coli Cell ◽

Spherical Particles ◽

Wall Structure ◽

Bacteriophage Infection ◽

Protein B

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YtfB, an OapA Domain-Containing Protein, Is a New Cell Division Protein in Escherichia coli

Journal of Bacteriology ◽

10.1128/jb.00046-18 ◽

2018 ◽

Vol 200 (13) ◽

Cited By ~ 2

Author(s):

Matthew A. Jorgenson ◽

Kevin D. Young

Keyword(s):

Escherichia Coli ◽

Cell Wall ◽

Cell Division ◽

Wall Structure ◽

Bacterial Cell Division ◽

Negative Bacterium ◽

Gram Negative ◽

Content Type ◽

Cell Division Protein ◽

Inner Membrane Protein

ABSTRACT While screening the Pfam database for novel peptidoglycan (PG) binding modules, we identified the OapA domain, which is annotated as a LysM-like domain. LysM domains bind PG and mediate localization to the septal ring. In the Gram-negative bacterium Escherichia coli , an OapA domain is present in YtfB, an inner membrane protein of unknown function but whose overproduction causes cells to filament. Together, these observations suggested that YtfB directly affects cell division, most likely through its OapA domain. Here, we show that YtfB accumulates at the septal ring and that its action requires the division-initiating protein FtsZ and, to a lesser extent, ZipA, an early recruit to the septalsome. While the loss of YtfB had no discernible impact, a mutant lacking both YtfB and DedD (a known cell division protein) grew as filamentous cells. The YtfB OapA domain by itself also localized to sites of division, and this localization was enhanced by the presence of denuded PGs. Finally, the OapA domain bound PG, though binding did not depend on the formation of denuded glycans. Collectively, our findings demonstrate that YtfB is a cell division protein whose function is related to cell wall hydrolases. IMPORTANCE All living cells must divide in order to thrive. In bacteria, this involves the coordinated activities of a large number of proteins that work in concert to constrict the cell. Knowing which proteins contribute to this process and how they function is fundamental. Here, we identify a new member of the cell division apparatus in the Gram-negative bacterium Escherichia coli whose function is related to the generation of a transient cell wall structure. These findings deepen our understanding of bacterial cell division.

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An Inhibitor of Exported Mycobacterium tuberculosis Glutamine Synthetase Selectively Blocks the Growth of Pathogenic Mycobacteria in Axenic Culture and in Human Monocytes: Extracellular Proteins as Potential Novel Drug Targets

Journal of Experimental Medicine ◽

10.1084/jem.189.9.1425 ◽

1999 ◽

Vol 189 (9) ◽

pp. 1425-1436 ◽

Cited By ~ 91

Author(s):

Günter Harth ◽

Marcus A. Horwitz

Keyword(s):

Cell Wall ◽

Mycobacterium Tuberculosis ◽

Glutamine Synthetase ◽

Extracellular Proteins ◽

Mononuclear Phagocytes ◽

Cell Wall Structure ◽

Host Cells ◽

Wall Structure ◽

Mycobacterial Cell ◽

Mycobacterial Cell Wall

Mycobacterium tuberculosis and other pathogenic mycobacteria export abundant quantities of proteins into their extracellular milieu when growing either axenically or within phagosomes of host cells. One major extracellular protein, the enzyme glutamine synthetase, is of particular interest because of its link to pathogenicity. Pathogenic mycobacteria, but not nonpathogenic mycobacteria, export large amounts of this protein. Interestingly, export of the enzyme is associated with the presence of a poly-l-glutamate/glutamine structure in the mycobacterial cell wall. In this study, we investigated the influence of glutamine synthetase inhibitors on the growth of pathogenic and nonpathogenic mycobacteria and on the poly-l-glutamate/glutamine cell wall structure. The inhibitor l-methionine-S-sulfoximine rapidly inactivated purified M. tuberculosis glutamine synthetase, which was 100-fold more sensitive to this inhibitor than a representative mammalian glutamine synthetase. Added to cultures of pathogenic mycobacteria, l-methionine- S-sulfoximine rapidly inhibited extracellular glutamine synthetase in a concentration-dependent manner but had only a minimal effect on cellular glutamine synthetase, a finding consistent with failure of the drug to cross the mycobacterial cell wall. Remarkably, the inhibitor selectively blocked the growth of pathogenic mycobacteria, all of which release glutamine synthetase extracellularly, but had no effect on nonpathogenic mycobacteria or nonmycobacterial microorganisms, none of which release glutamine synthetase extracellularly. The inhibitor was also bacteriostatic for M. tuberculosis in human mononuclear phagocytes (THP-1 cells), the pathogen's primary host cells. Paralleling and perhaps underlying its bacteriostatic effect, the inhibitor markedly reduced the amount of poly-l-glutamate/glutamine cell wall structure in M. tuberculosis. Although it is possible that glutamine synthetase inhibitors interact with additional extracellular proteins or structures, our findings support the concept that extracellular proteins of M. tuberculosis and other pathogenic mycobacteria are worthy targets for new antibiotics. Such proteins constitute readily accessible targets of these relatively impermeable organisms, which are rapidly developing resistance to conventional antibiotics.

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Characterization of Conserved and Novel Septal Factors inMycobacterium smegmatis

Journal of Bacteriology ◽

10.1128/jb.00649-17 ◽

2018 ◽

Vol 200 (6) ◽

Cited By ~ 13

Author(s):

Katherine J. Wu ◽

Jenna Zhang ◽

Catherine Baranowski ◽

Vivian Leung ◽

E. Hesper Rego ◽

...

Keyword(s):

Escherichia Coli ◽

Cell Wall ◽

Model Organisms ◽

Wall Structure ◽

Cross Wall ◽

Content Type ◽

A Cell ◽

Mediate Cell ◽

Mycobacterial Cell Wall ◽

Regulatory Functions

ABSTRACTSeptation in bacteria requires coordinated regulation of cell wall biosynthesis and hydrolysis enzymes so that new septal cross-wall can be appropriately constructed without compromising the integrity of the existing cell wall. Bacteria with different modes of growth and different types of cell wall require different regulators to mediate cell growth and division processes. Mycobacteria have both a cell wall structure and a mode of growth that are distinct from well-studied model organisms and use several different regulatory mechanisms. Here, usingMycobacterium smegmatis, we identify and characterize homologs of the conserved cell division regulators FtsL and FtsB, and show that they appear to function similarly to their homologs inEscherichia coli. We identify a number of previously undescribed septally localized factors which could be involved in cell wall regulation. One of these, SepIVA, has a DivIVA domain, is required for mycobacterial septation, and is localized to the septum and the intracellular membrane domain. We propose that SepIVA is a regulator of cell wall precursor enzymes that contribute to construction of the septal cross-wall, similar to the putative elongation function of the other mycobacterial DivIVA homolog, Wag31.IMPORTANCEThe enzymes that build bacterial cell walls are essential for cell survival but can cause cell lysis if misregulated; thus, their regulators are also essential. The number and nature of these regulators is likely to vary in bacteria that grow in different ways. The mycobacteria are a genus that have a cell wall whose composition and construction vary greatly from those of well-studied model organisms. In this work, we identify and characterize some of the proteins that regulate the mycobacterial cell wall. We find that some of these regulators appear to be functionally conserved with their structural homologs in evolutionarily distant species such asEscherichia coli, but other proteins have critical regulatory functions that may be unique to the actinomycetes.

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Inhibition of Respiration of Candida albicans by Small Molecules Increases Phagocytosis Efficacy by Macrophages

mSphere ◽

10.1128/msphere.00016-20 ◽

2020 ◽

Vol 5 (2) ◽

Author(s):

Shuna Cui ◽

Minghui Li ◽

Rabeay Y. A. Hassan ◽

Anna Heintz-Buschart ◽

Junsong Wang ◽

...

Keyword(s):

Cell Wall ◽

Candida Albicans ◽

Plasma Membrane ◽

Energy Metabolism ◽

Unsaturated Fatty Acids ◽

Immune Defense ◽

Host Cells ◽

Wall Structure ◽

Content Type ◽

Metabolic Studies

ABSTRACT Candida albicans adapts to various conditions in different body niches by regulating gene expression, protein synthesis, and metabolic pathways. These adaptive reactions not only allow survival but also influence the interaction with host cells, which is governed by the composition and structure of the fungal cell wall. Numerous studies had shown linkages between mitochondrial functionality, cell wall integrity and structure, and pathogenicity. Thus, we decided to inhibit single complexes of the respiratory chain of C. albicans and to analyze the resultant interaction with macrophages via their phagocytic activity. Remarkably, inhibition of the fungal bc1 complex by antimycin A increased phagocytosis, which correlated with an increased accessibility of β-glucans. To contribute to mechanistic insights, we performed metabolic studies, which highlighted significant changes in the abundance of constituents of the plasma membrane. Collectively, our results reinforce the strong linkage between fungal energy metabolism and other components of fungal physiology, which also determine the vulnerability to immune defense reactions. IMPORTANCE The yeast Candida albicans is one of the major fungal human pathogens, for which new therapeutic approaches are required. We aimed at enhancements of the phagocytosis efficacy of macrophages by targeting the cell wall structure of C. albicans, as the coverage of the β-glucan layer by mannans is one of the immune escape mechanisms of the fungus. We unambiguously show that inhibition of the fungal bc1 complex correlates with increased accessibilities of β-glucans and improved phagocytosis efficiency. Metabolic studies proved not only the known direct effects on reactive oxygen species (ROS) production and fermentative pathways but also the clear downregulation of the ergosterol pathway and upregulation of unsaturated fatty acids. The changed composition of the plasma membrane could also influence the interaction with the overlying cell wall. Thus, our work highlights the far-reaching relevance of energy metabolism, indirectly also for host-pathogen interactions, without affecting viability.

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