Mutations in the genes encoding enzymes responsible for the incorporation of D-Ala into the cell wall of Lactococcus lactis affect autolysis. An L. lactis alanine racemase (alr) mutant is strictly dependent on an external supply of D-Ala to be able to synthesize peptidoglycan and to incorporate D-Ala in the lipoteichoic acids (LTA). The mutant lyses rapidly when D-Ala is removed at mid-exponent...

PCR was used to identify penicillin resistance in 1,062 clinical isolates of Streptococcus pneumoniae. Three sets of primers were designed to amplify (i) a 240-bp fragment of the penicillin-binding protein (PBP) 2B gene (pbp2b) of penicillin-susceptible S. pneumoniae (PSSP), (ii) a 215-bp fragment of the class A mutations of the pbp2b gene present in penicillin-resistant S. pneumoniae, and (iii...

A Bacillus anthracis virulence plasmid-encoded peptidoglycan hydrolase (AmiA) with sequence similarity to N-acetylmuramoyl-L-alanine amidases hydrolyzes peptidoglycan independently of cell wall binding. Residues H341, E355, H415, and E486 are absolutely required for catalysis. Many AmiA paralogs are fused to different sorting signals, suggesting that these modular proteins result from domain sh...

Natural competence for genetic transformation is the best-characterized feature of the major human pathogen Streptococcus pneumoniae. Recent studies have shown the virulence of competence-deficient mutants to be attenuated, but the nature of the connection between competence and virulence remained unknown. Here we document the release, triggered by competent cells, of virulence factors (e.g., t...

Acutolysin A, a protein isolated from the venom of Chinese Five-pace snake (Agkistrodon acutus) has shown marked hemorrhagic and proteolytic activities. In the present study, the effects of metal ions and an inhibitor EDTA on the fluorescence and function of autolysin A have been studied, by following fluorescence and activity measurements. Acutolysin A contains a Ca(2+)-binding site, which pro...

The majority (591 of 791, or 76%) of Streptococcus pneumoniae clinical isolates examined showed the presence of two or more chromosomal SmaI fragments that hybridized with the lytA-specific DNA probe. Only one of these fragments, frequently having an approximate molecular size of 90 kb, was shown to carry the genetic determinant of the pneumococcal autolysin (N-acetylmuramic acid-L-alanine amid...

The major autolysins (Atl) of Staphylococcus epidermidis and S. aureus play an important role in cell separation, and their mutants are also attenuated in virulence. Therefore, autolysins represent a promising target for the development of new types of antibiotics. Here, we report the high-resolution structure of the catalytically active amidase domain AmiE (amidase S. epidermidis) from the maj...

Tyrosine phosphorylation has long been recognized as a crucial post-translational regulatory mechanism in eukaryotes. However, only in the past decade has recognition been given to the crucial importance of bacterial tyrosine phosphorylation as an important regulatory feature of pathogenesis. This study describes the effect of tyrosine phosphorylation on the activity of a major virulence factor...