Influence of pH on the transition from yeast-like cells to chlamydospores in Aureobasidium pullulans.

When A. pullulans is grown on a glucose medium with a limiting nitrogen source and low buffer capacity, the yeast-like cells that are originally present undergo a transition to chlamydospores. The initial pH must be around 6 for the transition to take place under optimal conditions. On the above-mentioned medium pH decreases to values below 2 in the first two days; if this decrease is prevented, either by buffering the medium or by repeatedly adjusting the pH to its original value no chlamydospores form.