Staphylococcus xylosus and Staphylococcus carnosus are used as starter cultures for sausage manufacturing. S. xylosus is frequently isolated in the food-processing plants environment while S. carnosus is rarely isolated. Thus, we have studied the ability of these two species to form biofilms on different abiotic supports. The S. carnosus strains are hydrophilic, adhere to hydrophilic supports but do not form biofilm. Some strains of S. xylosus are hydrophilic, others are moderately hydrophobic and all form biofilms whatever the support. S. xylosus C2a, selected as model strain, forms thick biofilms with intercellular aggregates separated by channels and embedded in a matrix composed of polysaccharides which synthesis seems independent of icaA gene. We have highlighted the atl and bap genes encoding surface proteins involved in biofilm formation in S. aureus. To study the whole of surface proteins involved, we have developed a method to analyse membrane and cell wall proteins. A total of 101 proteins was identified whose 51 are predicted as surface proteins and only 9 proteins are common to the two fractions. The comparison of protein patterns of cell wall, membrane and intracellular fractions revealed a differential expression of 115 proteins which 74 are over-expressed in sessile cells and 41 in planktonic cells. This study revealed the modification of several metabolic pathways. Their analysis will allow to better predict the mechanisms taking place in S. xylosus during its growth in biofilm.
