Abstract
The biofilm associated protein (Bap) is recognised as the essential component for biofilm formation in Staphylococcus aureus V329 and has been predicted as important for other species as well. Although Bap orthologs are also present in most S. xylosus strains, their contribution to biofilm formation has not yet been demonstrated. In this study, different experimental approaches were used to elucidate the effect of Bap on biofilm formation in S. xylosus and the motif structure of two biofilm-forming S. xylosus strains TMW 2.1023 and TMW 2.1523 was compared to Bap of S. aureus V329. We found that despite an identical structural arrangement into four regions, Bap from S. xylosus differs in key factors to Bap of S. aureus, i.e., isoelectric point of aggregation prone Region B, protein homology and type of repeats. Disruption of bap had no effect on aggregation behavior of selected S. xylosus strains and biofilm formation was unaffected (TMW 2.1023) or at best slightly reduced under neutral conditions (TMW 2.1523). Further, we could not observe any typical characteristics of a S. aureus Bap-positive phenotype such as functional impairment by calcium addition and rough colony morphology on congo red agar (CRA). A dominating role of Bap in cell aggregation and biofilm formation as reported mainly for S. aureus V329 was not observed. In contrast, this work demonstrates that functions of S. aureus Bap cannot easily be extrapolated to S. xylosus Bap, which appears as non-essential for biofilm formation in this species. We therefore suggest that biofilm formation in S. xylosus follows different and multifactorial mechanisms.
Highlights
IntroductionStaphylococcus (S.) xylosus is a Gram-positive, coagulase-negative commensal of mammal skin with a biotechnological relevance, as it is commonly used as a starter organism for raw sausage fermentation [1]
We investigated whether S. xylosus and its bap mutants show typical phenotypic characteristics and differences, as they have been reported in biofilm associated protein (Bap)-positive S. aureus strains and its respective bap mutants
In this study different experimental approaches were used to evaluate the impact of Bap in S. xylosus on its anticipated general role in biofilm formation and multicellular behavior
Summary
Staphylococcus (S.) xylosus is a Gram-positive, coagulase-negative commensal of mammal skin with a biotechnological relevance, as it is commonly used as a starter organism for raw sausage fermentation [1]. For persistence in such environments, surface colonization and the formation of biofilms are anticipated as important traits. Biofilm formation is a common property of many bacteria and describes a state where cells are embedded in an extracellular matrix, mainly consisting of exopolysaccharides, proteins and extracellular DNA [2]. If biofilms are of a mainly proteinaceous nature, surface proteins play a prominent role in primary adhesion and biofilm maturation as they can either interact with surface structures on adjacent cells or form amyloid structures that promote cellular aggregation [4]. Known surface proteins influencing proteinaceous biofilm matrix assembly include fibronectin binding proteins (FnBPs), Staphylococcus aureus surface protein G (SasG) and the biofilm associated protein (Bap) [5,6]
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