PHYSIOLOGICAL-STUDIES ON THE EFFECT OF CA2-CEREVISIAE( ON THE DURATION OF THE LAG PHASE OF SACCHAROMYCES)

Cell multiplication and growth of Saccharomyces cereviseae were follow ed in 2-ml test tubes containing Wickerham's synthetic medium or very dilute synthetic media supplemented in various ways. The ability of th e cell cultures to leave the lag phase and enter the exponential phase of growth was investigated. Multiplication was assessed by microscopi cal observation. The results showed great differences in times require d for the cultures to leave the lag phases and begin multiplication. I n Wickerham's medium, all cultures grew well 6 h after inoculation. In the dilute medium, several days elapsed before all the cultures grew. These cultures went into exponential growth with approximately first order kinetics. In the unsupplemented medium, the 'half-lives' in the lag phase were about 28 h. Addition of either Ca2+ or Ca2+ plus A23187 (calcimycin) reduced the half-lives to 10 and 6 h, respectively. The doubling times in the exponential phases of growth were not shortened by these additions. We suggest that Ca(2+)plays a crucial role as a si gnal to switch on the mode of cell proliferation in S. cerevisiae.