Functional and structural characterization of PaeM, a colicin M-like bacteriocin produced by Pseudomonas aeruginosa.

Colicin M (ColM) is the only enzymatic colicin reported to date that inhibits cell wall peptidoglycan biosynthesis. It catalyzes the specific degradation of the lipid intermediates involved in this pathway, thereby provoking lysis of susceptible Escherichia coli cells. A gene encoding a homologue of ColM was detected within the exoU-containing genomic island A carried by certain pathogenic Pseudomonas aeruginosa strains.

The peptidoglycan of Mycobacterium abscessus is predominantly cross-linked by L,D-transpeptidases.

Few therapeutic alternatives remain for the treatment of infections due to multiresistant Mycobacterium abscessus. Here we show that the peptidoglycans of the "rough" and "smooth" morphotypes contain predominantly 3→3 cross-links generated by l,d-transpeptidases, indicating that these enzymes are attractive targets for the development of efficient drugs.

The beta-lactam-sensitive D,D-carboxypeptidase activity of Pbp4 controls the L,D and D,D transpeptidation pathways in Corynebacterium jeikeium.

Corynebacterium jeikeium is an emerging nosocomial pathogen responsible for vascular catheters infections, prosthetic endocarditis and septicemia. The treatment of C. jeikeium infections is complicated by the multiresistance of clinical isolates to antibiotics, in particular to beta-lactams, the most broadly used class of antibiotics.

Human- and plant-pathogenic Pseudomonas species produce bacteriocins exhibiting colicin M-like hydrolase activity towards peptidoglycan precursors.

Genes encoding proteins that exhibit similarity to the C-terminal domain of Escherichia coli colicin M were identified in the genomes of some Pseudomonas species, namely, P. aeruginosa, P. syringae, and P.

The peptidoglycan of stationary-phase Mycobacterium tuberculosis predominantly contains cross-links generated by L,D-transpeptidation.

Our understanding of the mechanisms used by Mycobacterium tuberculosis to persist in a "dormant" state is essential to the development of therapies effective in sterilizing tissues. Gene expression profiling in model systems has revealed a complex adaptive response thought to endow M. tuberculosis with the capacity to survive several months of combinatorial antibiotic treatment.

Specificity of L,D-transpeptidases from gram-positive bacteria producing different peptidoglycan chemotypes.

We report here the first direct assessment of the specificity of a class of peptidoglycan cross-linking enzymes, the L,D-transpeptidases, for the highly diverse structure of peptidoglycan precursors of Gram-positive bacteria. The lone functionally characterized member of this new family of active site cysteine peptidases, Ldt(fm) from Enterococcus faecium, was previously shown to bypass the D,D-transpeptidase activity of the classical penicillin-binding proteins leading to high level cross-resistance to glycopeptide and beta-lactam antibiotics. Ldt(fm) homologues from Bacillus subtilis (Ldt(Bs)) and E.

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)).