The GTPase CpgA is implicated in the deposition of the peptidoglycan sacculus in Bacillus subtilis.

Depletion of the Bacillus subtilis GTPase CpgA produces abnormal cell shapes, nonuniform deposition of cell wall, and five- to sixfold accumulation of peptidoglycan precursors. Nevertheless, the inherent structure of the cell wall appeared mostly unchanged. The results are consistent with CpgA being involved in coordinating normal peptidoglycan deposition.

Inactivation of a subpopulation of human neutrophils by exposure to ultrahigh-molecular-weight polyethylene wear debris.

Polymorphonuclear neutrophils, a first line of defence against invading microbial pathogens, may be attracted by inflammatory mediators triggered by ultrahigh-molecular-weight polyethylene (UHMWPE) wear particles released from orthopaedic prostheses. Phagocytosis of UHMWPE particles by neutrophils may indirectly compromise their phagocytic-bactericidal mechanisms, thus enhancing host susceptibility to microbial infections. In an in vitro assay, pre-exposure of purified human neutrophils to UHMWPE micrometre- and submicrometre-sized wear particles interfered with subsequent Staphylococcos aureus uptake in a heterogeneous way, as assessed by a dual label fluorescence microscopic assay that discriminated intracellular rhodamine-labelled UHMWPE particles from fluorescein isothiocyanate-labelled S.

Exploring the role of the CTL epitope region of listeriolysin O in the pathogenesis of Listeria monocytogenes.

Listeria monocytogenes is a facultative intracellular bacterial pathogen responsible for severe opportunistic infections in humans and animals. The secreted cholesterol-dependent cytolysin, listeriolysin O (LLO), mediates phagosomal escape and allows bacterial growth in the cytosol of infected cells. In order to identify new LLO determinants participating in bacterial pathogenesis, this study focused on a major target of LLO proteolytic cleavage in vitro, the CTL epitope region (residues 91-99).

Gap, a mycobacterial specific integral membrane protein, is required for glycolipid transport to the cell surface.

The cell envelope of mycobacteria is a complex multilaminar structure that protects the cell from stresses encountered in the environment, and plays an important role against the bactericidal activity of immune system cells. The outermost layer of the mycobacterial envelope typically contains species-specific glycolipids. Depending on the mycobacterial species, the major glycolipid localized at the surface can be either a phenolglycolipid or a peptidoglycolipid (GPL).

Role of FliF and FliI of Listeria monocytogenes in flagellar assembly and pathogenicity.

Flagellar structures have been shown to participate in virulence in a variety of intestinal pathogens. Here, we have identified two potential flagellar genes of Listeria monocytogenes: lmo0713, encoding a protein similar to the flagellar basal body component FliF, and lmo0716, encoding a protein similar to FliI, the cognate ATPase energizing the flagellar export apparatus. Expression of fliF and fliI appears to be downregulated at 37 degrees C, like that of flaA, encoding flagellin.

The svpA-srtB locus of Listeria monocytogenes: fur-mediated iron regulation and effect on virulence.

In Listeria monocytogenes the promoter region of the svpA-srtB locus contains a well-conserved Fur box. We characterized the iron-regulation of this locus: real-time polymerase chain reaction analyses and anti-SvpA immunoblots showed that, in response to iron deprivation svpA transcription and SvpA production markedly increased (80-fold and 10-fold respectively), when initiated by either the addition of the iron chelator 2,2'-bipyridyl to BHI media, or by growth in iron-restricted minimal media. Green fluorescent protein (GFP) reporter constructs also showed increased activity of the svpA-srtB promoter in Escherichia coli (37-fold) and in L.

Differential roles of multiple signal peptidases in the virulence of Listeria monocytogenes.

Most bacteria contain one type I signal peptidase (Spase I) for cleavage of signal peptides from exported and secreted proteins. Here, we identified a locus encoding three contiguous Spase I genes in the genome of Listeria monocytogenes. The deduced Sip proteins (denoted SipX, SipY and SipZ) are significantly similar to SipS and SipT, the major SPase I proteins of Bacillus subtilis (38% to 44% peptidic identity).

Maturation of lipoproteins by type II signal peptidase is required for phagosomal escape of Listeria monocytogenes.

Lipoproteins of Gram-positive bacteria are involved in a broad range of functions such as substrate binding and transport, antibiotic resistance, cell signaling, or protein export and folding. Lipoproteins are also known to initiate both innate and adaptative immune responses. However, their role in the pathogenicity of intracellular microorganisms is yet poorly understood.

Modification of the signal sequence cleavage site of listeriolysin O does not affect protein secretion but impairs the virulence of Listeria monocytogenes.

Listeriolysin O (LLO, hly-encoded), a major virulence factor secreted by the bacterial pathogen Listeria monocytogenes, is synthesized as a precursor of 529 residues. To impair LLO secretion, the four residues of the predicted signal sequence cleavage site (EA-KD) were deleted and the mutant LLO protein was expressed in a hly-negative derivative of L. monocytogenes.

Capacity of ivanolysin O to replace listeriolysin O in phagosomal escape and in vivo survival of Listeria monocytogenes.

Listeriolysin O (LLO, hly-encoded) is a major virulence factor secreted by the pathogen Listeria monocytogenes. The amino acid sequence of LLO shows a high degree of similarity with that of ivanolysin O (ILO), the cytolysin secreted by the ruminant pathogen Listeria ivanovii. Here, it was tested whether ILO could functionally replace LLO by expressing the gene encoding ILO under the control of the hly promoter, in an hly-deleted strain of L.

Critical role of the N-terminal residues of listeriolysin O in phagosomal escape and virulence of Listeria monocytogenes.

A putative PEST sequence was recently identified close to the N-terminus of listeriolysin O (LLO), a major virulence factor secreted by the pathogenic Listeria monocytogenes. The deletion of this motif did not affect the secretion and haemolytic activity of LLO, but abolished bacterial virulence. Here, we first tested whether the replacement of the PEST motif of LLO by two different sequences, with either a very high or no PEST score, would affect phagosomal escape, protein stability and, ultimately, the virulence of L.

Balance between two transpeptidation mechanisms determines the expression of beta-lactam resistance in Enterococcus faecium.

The d,d-transpeptidase activity of high molecular weight penicillin-binding proteins (PBPs) is essential to maintain cell wall integrity as it catalyzes the final cross-linking step of bacterial peptidoglycan synthesis. We investigated a novel beta-lactam resistance mechanism involving by-pass of the essential PBPs by l,d-transpeptidation in Enterococcus faecium. Determination of the peptidoglycan structure by reverse phase high performance liquid chromatography coupled to mass spectrometry revealed that stepwise selection for ampicillin resistance led to the gradual replacement of the usual cross-links generated by the PBPs (d-Ala(4) --> d-Asx-Lys(3)) by cross-links resulting from l,d-transpeptidation (l-Lys(3) --> d-Asx-Lys(3)).

Biogenesis of Leishmania-harbouring parasitophorous vacuoles following phagocytosis of the metacyclic promastigote or amastigote stages of the parasites.

Protozoan parasites Leishmania alternate between a flagellated promastigote form and an amastigote form. In their mammalian hosts, Leishmania survive and multiply in macrophages. Both forms can be internalized by these host cells at different stages of the infectious process and eventually establish themselves within parasitophorous vacuoles exhibiting phagolysosomal properties.