Changes in cytochrome levels during growth of the yeast-like fungus Aureobasidium pullulans

Cytochromes of Aureobasidium pullulans have been identified and partially characterized using low-temperature and carbon-monoxide-difference spectroscopy. The presence of a-, b-, and c-type cytochromes is demonstrated, as are other unidentified redox components. During exponential growth in batch culture, cytochrome levels showed complex changes. Changes in respiration rates and in the levels of cytochrome a+a₃ closely paralleled cellular growth: both increased exponentially until stationary phase, when no further increase occurred. The b- and c-type cytochromes showed biphasic increases, initially doubling every, generation time and then increasing more slowly during the stationary phase. Sensitivity of respiration to 100μM potassium cyanide gradually decreased during exponential growth, falling from virtually 100% inhibition after about 20 h growth to 30% inhibition in the stationary phase. The results suggest that in stationary-phase cultures, an alternative cyanide-insensitive but salicylhydroxamic-acid-sensitive terminal oxidase also operates.