Eeffect of pH on growth in a respiration‐deficient mutant of Saccharomyces cerevisiae

Abstract

AbstractThe effects of pH on the budding cycle of a respiration‐deficient mutant of Saccharomyces cerevisiae were investigation by monitoring the time course of bud development on single cells. The volume of each bud was measured at various time intervals between the inception of its development and inception of development of the next bud on the mother cell. A previous report that the budding cycle consisted of two phases (a rapid‐growth phase and a slow‐growth phase) was confirmed. With increase in pH from 3.8 to 6.0 the budding cycle shortened as a result of both increase in rate of the rapid‐growth phase and decrease in the duration of the slow‐growth phase. Although further increase in pH to 7.4 further increased the rate of the rapid‐growth phase, the budding cycle lengthened as a result of an increase in time lag and increase in duration of the slow‐growth phase. The growth rate, in terms of bud volume, conformed with the expression: (1/V)(dV/dτ) = ξ exp(–V/η), where the values of ξ and η were dependent on pH. The cell volume distribution in a batch culture was compared with the cell volume distribution calculated from the growth curve of a single bud. Similarities in the curves suggested that the growth pattern of a whole culture reflected the growth pattern of a single cell.