FACTORS WHICH CONTROL MAXIMAL GROWTH OF BACTERIA

Abstract

Sinclair , N. A. (Washington State University, Pullman) and J. L. Stokes . Factors which control maximal growth of bacteria. J. Bacteriol. 83: 1147–1154. 1962.—In a chemically defined medium containing 1% glucose and 0.1% (NH 4 ) 2 SO 4 , both of these compounds are virtually exhausted by the growth of Pseudomonas fluorescens . If these carbon, energy, and nitrogen sources are added back to the culture filtrate, maximal growth to the level of the original culture is obtained. This process can be repeated several times with the same results. Eventually, however, the supply of minerals in the culture limits growth. When the nutrient levels are raised to 3% glucose and 0.3% (NH 4 ) 2 SO 4 , lack of oxygen and low pH limit growth before the supply of nutrients is exhausted. There is no evidence that specific autoinhibitory substances are produced either in chemically defined or complex nitrogenous media or that physical crowding of the cells limits growth. The results with Escherichia coli are similar to those with P. fluorescens . However, after a few growth cycles aerobically and after only one growth cycle anaerobically, inhibitory substances, probably organic acids, accumulate and limit growth.