Abstract
Toennies, G. (Institute for Cancer Research, Philadelphia, Pa.), L. Iszard, N. B. Rogers, and G. D. Shockman. Cell multiplication studied with an electronic particle counter. J. Bacteriol. 82:857-866. 1961.-Suitable conditions are described for the application of the Counter electronic particle counter to the study of bacterial number and particle size distribution in growing cultures. When Streptococcus faecalis and Escherichia coli were each grown in a different medium, exponential growth was accompanied by a continuous decrease in average particle size. The average apparent particle volume of S. faecalis decreased by about 50% in five generations. Microscopic studies of S. faecalis indicated that this was due to a decrease in the average chain length of the cultures. The following observations concerning average particle size during exponential growth of S. faecalis in a synthetic medium were made: (i) A decreased concentration of tryptophan, serine, or proline resulted in a significant decrease in average particle size. Similar changes in numerous other nutrients produced no or only minor changes. (ii) The addition of a cytoplasmic extract prepared from exponentially growing cells resulted in changes similar to those resulting from the partial withdrawal from the medium of certain nutrients. (iii) The effect of the cytoplasmic extract could be counteracted by the addition of tryptophan. (iv) A limited survey, including the effects of the rate of exponential growth, mechanical agitation, the presence of indoleacetic acid, indole, kinetin, lysozyme, or ascorbate, disclosed no additional factor which significantly influenced the particle size distribution.