BEHAVIOR OF ESCHERICHIA COLI B IN SULFATE-LIMITED MEDIUM

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Abstract
The sulfur metabolism of E. coli B in glucose–salts medium was studied. When sulfate was omitted from the medium, a population of washed, log phase cells increased in both turbidity and plate count in a manner suggesting two, apparently different, endogenous pools of sulfur-containing materials. In addition, it was found that the sulfur-deficient medium contained a small but significant level of available sulfur. This contaminating exogenous sulfur could be removed from the medium by incubation of the cell suspensions for 9–10 hours. Afterward, the starved cells were removed and replaced by cells in any desired state. Starved cells grew briefly, utilizing the sulfur impurities in the standard deficient medium, but began to die soon after reaching the maximum population. When the additions were small, added sulfate induced increases in turbidity by suspensions of starved cells after lag periods. Further, a sensitive turbidimetric analysis of the response of starved cells by an extrapolation method as a function of the amount of added sulfate revealed that no level of exogenous sulfate could be detected which did not stimulate growth. Therefore, no threshold or maintenance level, at least above 10−10 mole/ml for 2.5 × 108 cells/ml, exists for sulfate. Implications of these findings are discussed.

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