Dual Role of the Oligopeptide Permease Opp3 during Growth of Staphylococcus aureus in Milk

Staphylococcus aureus RN6390 presents a diauxic growth in milk, due to amino acid limitation. Inactivation of the oligopeptide permease Opp3 (dedicated to the nitrogen nutrition of the strain) not only affects the growth of the strain but also results in reduced expression levels of three major extracellular proteases.Staphylococcus aureus is a ubiquitous gram-positive pathogen commonly found in the environment. Some S. aureus strains are able to produce enterotoxins that cause food poisoning (6). In France, contaminated dairy products are the main source of staphylococcal food-borne disease outbreaks (3). Thus, the development of this bacterium in milk is a major concern for the safety of dairy products. Our objective was to evaluate the growth of S. aureus in milk, with special attention focused on the role of the peptide transport systems.