GROWTH OF ESCHERICHIA COLI IN DILUTED COMPLEX MEDIA

Abstract

Escherichia coli cells were cultured at 20° in variously diluted peptoneyeast extract media, of which the highest concentrations of the components were 10g and 5g, respectively, in 1l. The average size of the log-phase cells grown in these media gave a minimum value at the dilution level of one-hundredth. ATP and protein contents per cell also gave minimum values in cells grown in media of a similar dilution level. Whereas, the adenylate energy charge remained unchanged at about 0.9 in cells grown in a wide range of the dilution. Growth rate and other physiological characteristics also changed with the dilution of culture medium. The pattern of change in growth rate as a function of medium concentration was definitely different from those in terms of mass-increase rate, RNA content per cell and rate of protein synthesis; the latter three characteristics gave the same patterns. The difference in the regulation of growth rate and cell mass in relation to medium concentration is discussed.