Resolution of cells by centrifugal elutriation.
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Blood Cell Count↗
Biomedical subjects
W D Grant
Publications and source records attributed to W D Grant.
Cell wall teichoic acid as a reserve phosphate source in Bacillus subtilis.
Although exponential growth of Bacillus subtilis 168 in a phosphate-limited medium halted with the exhaustion of inorganic phosphate, the bacteria continued to grow at a slower rate for a further 3 to 4 h at 37 degrees C. This postexponential growth in the absence of an exogenous phosphate supply was accompanied by a loss of teichoic acid from the cell walls of the bacteria. Quantitative analysis of walls and culture fluids showed that the phosphate loss from the walls could not be accounted for by an increase in phosphate-containing compounds in the medium, which implied that the cells were using their own wall teichoic acids to supply phosphate necessary for growth. Addition of exogenous teichoic acid to phosphate-starved cultures resulted in stimulation of growth and in the simultaneous disappearance of teichoic acid phosphate from the medium. It is proposed that teichoic acids, which can contain more than 30% of the total phosphorus of exponential-phase cells, can be used as a reserve phosphate source when the bacteria are starved for inorganic phosphate.
Bacillus subtilis↗
Temperature-sensitive mutants of the slime mould Physarum polycephalum. I. Mutants of the amoebal phase.
A replica plating method for isolating it amoebal mutants of Physarum polycephalum has been devised. Temperature-sensitive mutations occur at a frequency after nitrosoguanidine mutagenesis of 10(-3) per survivor, are stable but are not usually expressed in the plasmodia formed from these amoebae in clones. Some of these mutants appear to be cell-cycle stage specific.
Cell Division↗
Temperature-sensitive mutants of the slime mould Physarum polycephalum. II. Mutants of the plasmodial phase.
Methods are described for the isolation and testing of temperature-sensitive plasmodial strains of Physarum polycephalum. Nineteen temperature-sensitive strains were found by screening plasmodia derived from mutagenised amoebae and the properties of these are described. A scheme is outlined for the detection of specific mitotic cycle lesions amongst temperature-sensitive strains, and the properties of a presumptive mitotic cycle mutant are described.
Cell Division↗
Microbial degradation of condensed tannins.
A strain of Penicillium adametzi Zaleski was isolated from enrichment cultures with condensed tannins as the carbon source. Low-molecular-weight condensed tannins, extracted and purified from Pinus radiata bark, were used as substrates for quantitative growth measurements on this fungus in defined culture conditions.
Penicillium↗
The control of mitosis in Physarum polycephalum: the effect of delaying mitosis and evidence for the operation of the control mechanism in the absence of growth.
Possible mechanisms coordinating the control of mitosis and DNA synthesis with growth were experimentally tested in Physarum polycephalum by the response of plasmodia to 2 different kinds of perturbation of the DNA:mass ratio. Mitosis and DNA synthesis were delayed without stopping growth either by the use of fluorodeoxyuridine (FUdR) or puromycin, in both cases the delayed mitosis was followed by a single shortened intermitotic period, as predicted by all the mechanisms considered and substantiating a basic assumption made that the time of mitosis is homeostatically controlled to maintain a constant DNA:mass ratio. When more than 50% of the DNA was destroyed by ultraviolet irradiation 2 consecutive mitoses could occur even when growth was completely stopped by starvation. This result can only be accounted for by 2 of the 5 models considered, a finding which agrees with the results of previous experiments which were also consistent with only these 2 mechanisms.
DNA↗