FIG. 3.

Survival rates of colony morphology mutants treated with 10% (vol/vol) n-hexadecane in the presence or absence of 100 μg of S-2 EPS per ml. Symbols: ●, S-2 in the absence of EPS; ■, R-1 in the absence of EPS; ⧫, R-2 in the absence of EPS; ⊞, R-1 in the presence of EPS; •, R-2 in the presence of EPS. Cells grown to the late logarithmic phase in YG were harvested by centrifugation at 4,000 × g for 10 min, washed twice with 5 ml of saline, and resuspended in 5 ml of saline. The cell suspensions were diluted 10⁴-fold, and 5 ml aliquots of the diluted cell suspensions were dispensed into sterile tubes containing 0, 2.5, 5, 12.5, 25, or 50 mg of n-hexadecane. Each sample was vortexed twice for 30 s with a 5-s interval between treatments and then left until complete separation of the aqueous and n-hexadecane layers occurred. An aliquot (1 ml) of the aqueous layer was transferred to a new tube and plated onto YG agar plates after appropriate dilution with saline. The plates were incubated at 30°C for 48 h.