Alternative sigma factor B reduces biofilm formation and stress response in milk-derived Staphylococcus aureus

Abstract

Staphylococcus aureus is one of the most important food-borne pathogens and shows strong tolerance to environmental stress. The functions of alternative sigma factor B (SigB) have been studied in S. aureus Newman and SH1000 (a derivative strain of S. aureus NCTC8325) isolated from human samples. However, the role of SigB in the stress response of food-borne S. aureus has not been reported. In this study, the functions of SigB involved in food-related stress responses and biofilm formation in S. aureus RMSA24 isolated from raw milk were investigated. The sigB mutant synthesized less biofilm than the wild-type strain and resulted in a nonpigmented phenotype. Our results indicated that SigB was essential for biofilm formation and staphyloxanthin biosynthesis. Furthermore, mutation of sigB provoked a decrease in resistance to heat, drying, and hydrogen peroxide. This study further confirmed that sigB is a transcription factor responding to biofilm formation and stress tolerance in S. aureus, and the findings of this study provide an important clue for further studying the control of biofilm formation and the tolerance to high temperature, drying, oxidation of S. aureus in the food processing environment.