Incorporation of phosphorus into phased cells ofCandida utilis using32P and33P

Abstract

Abstract. Changes in phosphorus metabolism were studied by examining the incorporation of a2p and aap into cells of Candida utilis growing in phased culture during a 6 h cell cycle and a post-cycle period of 6 h. Three different chemically defined media were used; these were phosphorus, nitrogen and carbon limited. The patterns of incorporation of phosphorus into RNA, DNA, lipid and cold water extractable phosphate fractions showed a non-uniform behaviour during both cell cycle and post-cycle periods. The patterns were different in all three types of media. The results showed that a cell can grow and develop at a fixed growth rate in different ways: so that the pattern of behaviour during a cell cycle is not stereotyped for a given doubling time, but largely depends upon the nutrient environment in which the cell exists.During the last 25 years an increasing awareness of the fundamental importance of the individual unit--the microbe, rather than the cell population, has developed in relation to the study of microbial growth and metabolism, so that new perspectives are becoming apparent within the discipline of microbiology (Dawson and Phillips, 1974). Nevertheless, our knowledge of such matters is still rudimentary.For a long time, the population in a batch culture has demonstrated the potential range and variability of microbial growth activity by the transient changes occurring within the sequence of its growth curve. Such studies restricted to the overall behaviour of the cell population ignores the microbe as an entity and limits information to the crude level of the mean performance of the cell population that changes as development proceeds in the closed system of culture (Herbert, 1961).With the advent of the open system of continuous flow culture, growth can be stabilised in a condition of equilibrium and, in a chemostat, examined as a steady state at any chosen growth rate.

Continuous fermentation — And new horizons

“…Some order is apparent in the variations of the 'cell cycle' patterns observed and awaits resolution. Early results (Dawson, 1966, Hampton and Dawson, 1969, Dawson and Craig, 1966, Glattli and Dawson, 1974, Miiller and Dawson, 1968 showed changes in protein, RNA, lipids, amino acid contents and other constituents; both with change of growth rate, and under different nutrient limited growth conditions. The changes for protein and RNA, are briefly illustrated as follows:…”

Effects of Nitrate and Phosphate Limitation on Cyclostat Growth of Two Freshwater Diatoms

“…J. Gotham, unpublished data). In Nand P-depleted, phased cultures of Cundidu utilis the timing of initiation of cell division also remains virtually unchanged, although when carbon sources are depleted the onset of division in this yeast occurs much earlier in the phased culture cycle (Glattli & Dawson, 1974). In the fast-growing marine diatom Thalussiosiru Juviatilis, Chisholm & Costello ( 1980) have observed an 8 h phase shift in the maximum for cell division between nutrient-unlimited and P-limited cyclostat cultures.…”