The effect of mycophenolic acid on the cell cycle of Candida albicans.

Mycophenolic acid inhibited the growth of Candida albicans. Cultures exposed to a concentration of 8.4 micrograms ml-1 mycophenolic acid were found to exhibit cell cycle arrest with two or more buds. Nuclear staining revealed that these were nucleate implying a possible defect in cytokinesis. The results are discussed in relation to the possible mode of action of mycophenolic acid.

The segregation of the 2 mu-based yeast plasmid pJDB248 breaks down under conditions of slow, glucose-limited growth.

The stability of the 2 mu-based yeast plasmid pJDB248 in Saccharomyces cerevisiae S150-2B(cir0) was investigated in glucose-limited chemostat culture. Plasmid-free cells were detected by loss of (plasmid-encoded) leucine prototrophy and confirmed by colony hybridization. The plasmid was considerably more stable at a high dilution rate (0.12 h-1) than at a lower dilution rate (0.05 h-1). The average plasmid copy number in the cells retaining the plasmid remained constant at approximately 50 in the high dilution rate culture whereas it rose to almost 600 in the slow dilution rate culture. However, in both cultures the overall plasmid level in the total population remained constant, indicating that plasmid segregation breaks down at the low growth rate. Similar experiments on the native 2 mu plasmid demonstrated high stability and no significant differences between the high and low growth rate cultures. It is postulated that the difference in behaviour between the native and chimeric plasmids is related to an interaction between the growth conditions and the loss of the D gene product.

Estimating the mode of growth of individual microbial cells from cell volume distributions.

Two new methods are derived for inferring the mode of growth of individual microbial cells from measurements made of the volume distributions of populations. One is based on statistics of the observed distribution and has the particular advantage that it is very easy to use. The second, which requires gradient centrifugation, yields the mode of growth directly, rather than by comparison with theoretically derived distributions. Both methods have been found to be more sensitive than those previously suggested.

Mating factor dependence of G1 cell cycle mutants of Saccharomyces cerevisiae.

Mutants in four G1 cdc strains of Saccharomyces cerevisiae were isolated which failed to show division arrest in the presence of α-factor. The cell cycle properties, terminal arrest morphology and mating competence of these mutants at the restrictive temperature were examined. The G1 specific arrest of the cdc 36 and cdc39 mutants is dependent upon the availability of an intact mating factor response system in Mat a cells. Cdc28 and cdc37 mutants exert their cell cycle blocks independently of the mating factor pathway. It is likely that the nature of the primary growth defect in cdc36 and cdc39 mutants is such that the α-factor pathway is activated in the absence of the pheromone at the restrictive temperature and that G1 arrest is a secondary consequence of a non-cycle specific event in such mutants.

Size at bud initiation for wild-type and petite yeast cells.

Cell size at bud initiation shows the same relationship to growth rate in wild-type and petite yeast cells. The nutrient-modulated size control is related to growth rate rather than a change from fermentative to oxidative metabolism.