Studies of Certain Factors Influencing the Size of Bacterial Populations

Abstract

Physical crowding, growth inhibiting hormones, depletion of food and accumulation of metabolites as limiting factors are discussed and experiments with Escherichia coli are presented which indicate that factors other than these initially act to limit the size of bacterial popxilations. Apparatus for the continuous renewal of food and elimination of metabolites is described. With this arrangement a high constant population level may be indefinitely maintained. Growth will not mount above a certain level even with metabolites reduced to a low degree. Addition of a readily utilizable source of energy during the stable level brings about an immediate rise in the population. The authors believe that cessation of growth may be due to changes in the availability of the nutrient material and the energy demand.