The Bacterial Growth Curve and the History of Species

Abstract

WHEN a nutrient solution is inoculated with a species of micro-organism, in pure culture, the curve obtained by plotting the population against the time is characteristic and conforms to a general type of growth curve; an initial period of slow increase in numbers being followed by a rapid rise in population which, in turn, is superseded by a decline. An example of such a curve, representing the growth of a species of Actinomyces (measured by the evolution of carbon dioxide) in glucose solution,¹ is given in Fig. 1. Winslow² recognises five phases in bacterial growth curves: (i) phase of adjustment, A—B; (ii) phase of increase, B—C; (iii) phase of crisis, C—D; (iv) phase of decrease, D—E; (v) phase of readjustment, E—F; it is worthy of remark that the diminution in numbers following the period of crisis appears to be due neither to a deficiency in the food supply nor to the formation of toxic substances.