Differential growth rates of Candida utilis mother and daughter cells under phased cultivation

Abstract

The yeast Candida utilis was continuously synchronized by the phased method of cultivation with the nitrogen source as the growth-limiting nutrient. The doubling time (phasing period) of celLs was 6 h. Both cell number and deoxyribonucleic acid synthesis showed a characteristic stepwise increase during the phased growth. The time of bud emergence coincided with the time of initiation of deoxyribonucleic acid synthesis. Size distribution studies combined with microscopic analysis showed that the cells expanded only during the unbudded phase of growth. Usually the cells stopped increasing in size about 30 min before bud emergence, and the arrest of the increase in cell volume coincided with the exhaustion of nitrogen from the medium. There was no net change in the volume of cells during the bud expansion phase of growth, suggesting that as the bud expanded, the volume of the mother portion of the cell decreased. After division the cells expanded slightly. The postdivision expansion of cells, unlike the growth before bud initiation, occurred in the absence of the growth-limiting nutrient. The newly formed daughter cells were smaller than the mother cells and expanded at a faster rate, so that both types of cells reached maximum size at the same time. Possible reasons for the different rates of expansion of mother and daughter cells are discussed. Mitchison (18) suggested that the cell cycle can be considered as two loosely coupled and temporally overlapping sequences ofevents. One is referred to as the DNA division cycle, and the other is referred to as the growth cycle. Cycle markers that can be identified with the DNA division cycle are the start and the finish of the S period, stages of mitosis, and cell division. Most of the macromolecular syntheses, including the production of step and peak enzymes and cell envelope synthesis, are considered to be part of the growth cycle. Under normal conditions of growth these cycles are coordinated. This is borne out by the fact that cells of a particular type display a characteristic and rather narrow range of sizes (7). Cell division without precisely controlled coordination between growth and DNA division cycles would result in the production of excessively large or infinitesimally small cells. However, the mechanism of this coordination is poorly understood. One suggestion is that attainment of a critical cell size might be a prerequisite for the continuation of the cellular events that lead to cell division (8). The existence of such "size control" over cell division has been verified in several microorganisms (4,7,8,10,32). t National Research Council publication no. 17960.The progression through the cell cycle of two newborn cells of equal size under the same environmental conditions would be expected to be at the same rate, so that the cells might attain the critical size at the same time. Most likely these cells would have the same generation time as well. However, if the newborn cells were not the same size, it is quite likely that the smaller cell would take a lo...

Single Cell Analysis inside Environmental Scanning Electron Microscope (ESEM)-Nanomanipulator System

“…The shape of the cells was assumed to be a prolate spheroid, and the volumes were calculated by using the formula V=(π/6)lw 2 , where V is the volume, l is the height, and w is the width at maximum circumference (diameter) (Johnston et al, 1977). Thomas et al (Thomas et al, 1980) reported about 38% difference in cell volume between fully separated mother and daughter cells of Candida utilis type of yeast cell. In our experiment, the volume difference of the mother and daughter cells is about 45% and this is reasonable since the daughter was not fully grown as it was still intact with its mother at the time of measurement.…”

Cutting Edge Nanotechnology

“…The shape of the cells was assumed to be a prolate spheroid, and the volumes were calculated by using the formula V=(π/6)lw 2 , where V is the volume, l is the height, and w is the width at maximum circumference (diameter) (Johnston et al, 1977). Thomas et al (Thomas et al, 1980) reported about 38% difference in cell volume between fully separated mother and daughter cells of Candida utilis type of yeast cell. In our experiment, the volume difference of the mother and daughter cells is about 45% and this is reasonable since the daughter was not fully grown as it was still intact with its mother at the time of measurement.…”

Cell synchrony and periodic behaviour in yeast populations

“…One portion is retained in the reactor for the subsequent cycle and the other is made available for "post-cycle'' studies (Dawson, 1969(Dawson, , 1970 and, unlike a pulsed chemostat, the entire nutrient environment is cycled, not just a single nutrient. The technique has been applied primarily to study cell cycle events in Candida utilis by Muller and Dawson (1968), Hampton and Dawson (1969), Dawson (1971Dawson ( , 1985b, Dawson et al (1976) and Thomas et al (1980aThomas et al ( , 1980b, but has also been used with E. coli (Anagnostopoulos, 197 1;Kepes andKepes, 1980, 1985), and B. subtilis (Maruyama et al, 1977). Figure 4 illustrates the type of data that can be collected from a continuous phased culture (Dawson, 1988), in this case Candida utilis with a cell cycle of 4 h duration followed by an 8 h post cycle period.…”