Based on this effect, we generated 5 derivatives of LAC that differed based on the functional status of sae and sarA relative to each other and assessed the impact on virulence and overall protein profiles, which led to the identification of 114 proteins that were present in significantly greater amounts (log2 fold-change >2.0) in virulent versus attenuated strains as defined by our osteomyelitis model (7). The gene discussed is LCT; the disease is osteomyelitis.