FIG. 1.

Growth and extracellular AI-2 production. Cultures of S. aureus NCTC8325 wild type (WT) and the luxS mutant (SX1) were inoculated into LB medium at time zero and at the indicated intervals. Growth was monitored, and aliquots were taken and filtered to remove cells. AI-2 activity in the supernatant was measured using the V. harveyi BB170 bioassay. The data shown represent the mean values of four parallel AI-2 bioassays. The fold induction of AI-2 in the wild type exceeded 100 when the OD₆₀₀ was 1.8.