Studies of Certain Factors Influencing the Size of Bacterial Populations

Abstract

Notwithstanding the wealth of investigation carried out on bacterial growth, relatively few consistent data are available on the intermediate phases; i.e., the phase of negative acceleration and closely related to it, the maximum stationary phase. It would be of interest to know why cells suddenly deviate from an orderly logarithmic growth process to one of progressively increasing generation time and why cells cease to multiply before spatial restrictions limit them. The literature lacks a convincing trend on any experimental basis. That there are conflicts of opinion and data is not surprising when one considers the vagaries of bacterial strains, the diversity of species requirements, and the difficulty of reproducing in one laboratory the exact experimental conditions in another. The present studies and others to follow are undertaken in an effort to reconcile if possible, by repeating and extending in one laboratory with a single strain of orgasm, investigations in this field. No special effort is made to review the literature. Henrici (1928) and Rahn (1932) have recently filled that need admirably. Since the physical factors of environment are subject to fairly accurate control, one may profitably turn to those of biochemical nature. A strain of E. coli has been selected for these studies by reason of the more extensive information available on its metabolism and the ease with which contaminants may be detected. After investigation of various counting techniques the plating method was used. Counting error was consistently within 5 per cent. 205