Yeast strains were grown in 1% yeast extract, 2% peptone, and 2% dextrose (YPD) liquid medium at 30°C overnight and then harvested and suspended in sterile phosphate-buffered saline (PBS). Optical density (OD) was measured with a spectrophotometer (Ultraspec 2000; Pharmacia Biotech, Princeton, NJ) at a wavelength of 600 nm (OD
600). A conversion factor of one OD
600 unit equivalent to 3 × 10
7 colony-forming units (CFU)/mL was used to estimate fungal concentration.
36,37 Triplicate samples of 3 × 10
5 CFU for each strain were inoculated into 25 mL M199 liquid media (Invitrogen, Grand Island, NY) at pH 6.0, 7.3, and 8.0 and incubated at 27°C with a shaking speed of 150 rpm.
C. albicans concentrations were determined spectrophotometrically at 1.5, 3, 4.5, 6, 9, 12, 15, and 24 hours postinoculation (PI). The doubling time for each strain at each pH was calculated from the slope of the linear regression equation describing the exponential growth phase. Student's
t-test was used for pairwise comparisons, and
P < 0.05 was considered statistically significant.