AN APPARATUS FOR THE GROWTH OF AEROBIC BACTERIA AND THE PREPARATION OF BACTERIOPHAGE

In the course of experiments on the preparation of T3 bacteriophage (Adams, 1950) for analytical purposes it was found, as is common, that large-scale cultures of Escherichia coli did not maintain exponential growth as long as do 10ml experiments run in test tubes. The present apparatus was designed to grow bacteria in optimum physiological condition on a practical scale. It has been found that with it results of small experiments can be duplicated on a 2-liter scale. There is no apparent reason why the design cannot be expanded.2 A simple bubbler in a test tube provides about 10 ml of air per minute per ml of culture. It has been shown that the yield of T3 is strongly dependent on the air flow rate (see table 1); the limiting factor in scaling up 10-ml experiments is thus primarily the air supply. Larger flasks even with several sintered glass disks or sintered-glass-tipped tubes were unsatisfactory because of the back pressure, excessive foaming, and still insufficient air supply. The foaming could be alleviated by an antifoam agent' and contact improved by mechanical agitation, but the relative rate of air throughput was always smaller than it was on the 10-ml scale. Since the air flow rate primarily determines the amount of oxygen dissolved (Wise, 1950), the growth of the E. coli and the yield of T3 bacteriophage did not reproduce the results of the small-scale cultures. The basic principle of the present apparatus is that of a circulating system using an air lift and a "cyclone" type of separator to break foam. Advantages, in addition to the excellent gas-liquid mixing and the large air flows that are possible, include (a) the ease and speed of sterilization of the apparatus and medium in situ; (b) temperature control at any desired temperature without a bath, incubator, or constant temperature room; (c) provision for sampling the culture at will without risking contamination; and (d) provision for filtering the effluent