Effect of farnesol on the growth and viability of P. brasiliensis yeast cells. (A) Growth curves of P. brasiliensis yeast cells incubated in the presence of different concentrations of farnesol. The number of cells at each specific time point was assessed by measuring the OD absorption at 630 nm, after vigorously shaking the cultures. The growth curve of each culture was prepared by plotting the logarithmic values of OD630 vs. incubation time. (B) Viability of P. brasiliensis yeast cells cultivated with different concentrations of farnesol after 15 days of growth in the absence, or in the presence of farnesol (2.5 to 50 μM). The MTT assay was performed as described in methods section. MTT formazan formation was measured at 490 nm by using a spectrophotometer.