The major autolysin ofStaphylococcus lugdunensis,AtlL, is involved in cell separation, stress-induced autolysis and contributes to bacterial pathogenesis

Abstract

Staphylococcus lugdunensis is a human skin commensal organism, but it is considered as a virulent Staphylococcus species. In a previous study, we described the first S. lugdunensis autolysin, AtlL. This enzyme displays two enzymatic domains and generates two peptidoglycan hydrolases, an N-acetylmuramoyl-l-alanine amidase and an N-acetylglucosaminidase. In this study, to further investigate the functions of this autolysin, a ΔatlL mutant was constructed. The microscopic examination of the mutant showed cell aggregates and revealed a rough outer cell surface demonstrating, respectively, the roles of AtlL in cell separation and peptidoglycan turnover. This ΔatlL mutant exhibited a lower susceptibility to Triton X-100-induced autolysis assays and appears to be more resistant to cell wall antibiotic-induced lysis and death compared with its parental strain. The atlL mutation affected the biofilm formation capacity of S. lugdunensis. Furthermore, the ΔatlL mutant showed trends toward reduced virulence using the Caenorhabditis elegans model. Overall, AtlL appears as a major cell wall autolysin of S. lugdunensis implicated in cell separation, in stress-induced autolysis and in bacterial pathogenesis.

Multi-Virulence-Locus Sequence Typing of Staphylococcus lugdunensis Generates Results Consistent with a Clonal Population Structure and Is Reliable for Epidemiological Typing

“…Besides theses virulence-associated loci, we analyzed the polymorphisms of the repeated sequences (atlL R2 and atlL R3 ) of the putative CWA domains of the AM and GL autolysins, respectively, generated by the proteolytic cleavage of the bifunctional murein hydrolase, AtlL (40). Indeed, AtlL might play a role in virulence, as it has been shown in vitro through biofilm formation and in vivo in the C. elegans model (41). As AtlL presents high identity percentage with all staphylococcal bifunctional autolysins (40,42,43), it might be involved in the internalization of the bacteria in the eukaryote cell (59).…”

“…Like AtlA and AtlE, AtlL of S. lugdunensis displays two enzymatic domains separated by three repeat domains (AtlL R1 to AtlL R3 ) and undergoes proteolytic processing to generate two extracellular peptidoglycan hydrolases, an N-acetylmuramoyl-L-alanine amidase (AM) and an N-acetylglucosaminidase (GL) with two (AtlL R1R2 ) and one (AtlL R3 ) repeated sequences harboring glycine tryptophan motifs, respectively (40). We recently reported that a ⌬atlL mutant showed a significant reduction in biofilm formation and virulence attenuation using the Caenorhabditis elegans model (41). Since the overall organization of the bifunctional precursor protein is highly conserved in all staphylococcal species (42), the virulence findings for AtlA and AtlE may thus also apply for the entire Staphylococcus genus (43).…”

Messages from the first International Conference on Clinical Metagenomics (ICCMg)

“…Most of these factors have been shown to be associated with greater virulence or immune evasion in animal models of staphylococcal infections [26][27][28][29][30][31][32][33][34][35][36]. We hypothesize that lysogeny has played a significant role in increasing the ability of the ST398 clone to cause infections in humans and to become rapidly established in hospital environments.…”

Characterization of Staphylococcus caprae Clinical Isolates Involved in Human Bone and Joint Infections, Compared with Goat Mastitis Isolates

“…In Staphylococcus lugdunensis, well known in BJI, the relative atlL autolysin is implicated in cell separation and in stress-induced autolysis. The atlL mutation affected the biofilm formation ability of S. lugdunensis and reduced virulence (36). The atlC gene was present in 86% of the isolates, but no specific biofilm phenotype was observed among atlC-negative strains, suggesting a complex process for biofilm formation with the implication of several genes and regulation.…”