The Growth of Bacteria with a Constant Food Supply

Abstract

Escherichia coli was cultivated in an apparatus which permits rigid control of temp., pH, aeration, and culture volume, and also allows food to be supplied at any desired rate by means of an automatic syringe mechanism. From a number of expts., detns. of total and viable cell populations were made and growth curves constructed. At each of the 2 rates of constant food supply used, an initial period in which the total and viable counts were both increasing was followed by a steady phase in which the viable counts remained constant or decreased slightly while the total cell counts steadily increased. When, in expts. which had reached the steady phase, the food supply was suddenly doubled, a 2d phase of cell multiplication similar to that in the initial period began and was succeeded by a 2d steady phase. When during the 1st steady phase the food supply was suddenly stopped, the total cell population remained constant but the viable cells decreased to a constant low level. The significance of the growth curves is discussed and approximate calculations made of the amt. of food used in the formation of a new E coli cell and in maintenance of a cell apart from reproduction. These amts. of Difco dehydrated broth are found to be 1.1 X 10-9 mg. and 0.4 to 0.5 X 10-9 mg. per 25 hrs., respectively.