Response of Log-phase Cells of Escherichia coli to Medium Limited in Both Sulfate and Phosphate

Abstract

In a study of the effects of a double nutritional deficiency, washed suspensions of log-phase cells of Escherichia coli increased in both turbidity and plate counts when incubated at 35 to 37 C in a medium deficient in sulfate and phosphate and buffered with tris(hydroxymethyl)aminomethane. The population approximately doubled within 6 to 9 hr, whereas the turbidity increased only 28 to 33% in the same period. Ribonucleic acid, deoxyribonucleic acid, and protein levels were followed, and changes were observed with time and deficiency state. Long-term experiments illustrated that a resulting population in a medium deficient in both sulfate and phosphate survived for 4 to 5 days, a longer period than that characteristic of the single deficiencies. Moreover, in media deficient in sulfate, E. coli possessed two completely distinct behavior patterns depending on the nature of the buffer used. In addition, a variation of one nutrient with a marked deficiency of the other suggested the existence of a controlling mechanism in E. coli which regulated the processes of cell division and survival, depending on the combination of conditions.