Fig 5.
Kinetics of competence development in S. infantarius. (A) Pheromone dependence of competence development. Aliquots of a CDM culture of strain 3AG-1ΔcomS at an OD of 0.5 were mixed with DNA (0.5 μg/ml) and the indicated amounts of SinComS9–15 peptide. After 40 min at 37°C, samples were diluted in M17 medium for expression and plating. Error bars represent standard deviations among triplicate determinations. (B) Temporal pattern of competence induction by XIP. After addition of 10 μM SinComS9–15 to a culture of 3AG-1ΔcomS in CDM at an OD of 0.3, 250-μl samples were exposed to DNA (2 μg/ml) for 3 min at the indicated times and then diluted 30-fold into M17 medium with 2 μg/ml of DNase. After expression, further dilutions were plated in M17-Rif agar to obtain an estimate of relative competence level. Error bars represent standard deviations among triplicate determinations.