Abstract
Staphylococcus xylosus forms biofilm embedded in an extracellular polymeric matrix. As extracellular DNA (eDNA) resulting from cell lysis has been found in several staphylococcal biofilms, we investigated S. xylosus biofilm in vitro by a microscopic approach and identified the mechanisms involved in cell lysis by a transcriptomic approach. Confocal laser scanning microscopy (CLSM) analyses of the biofilms, together with DNA staining and DNase treatment, revealed that eDNA constituted an important component of the matrix. This eDNA resulted from cell lysis by two mechanisms, overexpression of phage-related genes and of cidABC encoding a holin protein that is an effector of murein hydrolase activity. This lysis might furnish nutrients for the remaining cells as highlighted by genes overexpressed in nucleotide salvage, in amino sugar catabolism and in inorganic ion transports. Several genes involved in DNA/RNA repair and genes encoding proteases and chaperones involved in protein turnover were up-regulated. Furthermore, S. xylosus perceived osmotic and oxidative stresses and responded by up-regulating genes involved in osmoprotectant synthesis and in detoxification. This study provides new insight into the physiology of S. xylosus in biofilm.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
We observed the architecture of the S. xylosus biofilm by recording the fluorescence of the labeled strain S. xylosus C2a-B2 and the stained extracellular DNA (eDNA) by TOTO-3 during the 48 h of incubation (Figure 1A)
An increasing amount of eDNA was measured in the S. xylosus biofilm during the incubation period, this increase being noticeable between 24 and 48 h, as evidenced by high values of biovolume, thickness and coverage
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Staphylococcus xylosus is a commensal species of the epithelium and mucous membranes of warm-blooded animals. It is frequently isolated from the skin of farm animals [1,2], its prevalence in foods of animal origin such as milk and milk products and fermented meat products [3,4]. S. xylosus colonizes the manufacturing environment of dry fermented sausage plants in relation to its ability to form biofilm [4,5]
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