LAG PHASE OF ESCHERICHIA COLI AS INFLUENCED BY X-RAYS TEMPERATURE AND NUTRIENT.

Abstract

Escherichia coli, following x irradiation, showed a prolonged lag phase of the growth curve. The logarithmic phase, once initiated, was not different from that of nonirradiated cells. The length of the increased lag phase following irradiation was dose dependent. When postirradiation incubation temperature was 15 deg C for 22 hours, the lag was not increased as much as it had been with immediate 37 deg C incubation. This shortening effect was not observed when cells were maintained without glucose for the 15 deg C period of 22 hours, Cells treated with 15 deg C, with or without glucose, showed a marked dose- rate dependence in terms of length of increased lag, an intermediate doserate causing the longest lag. Colonies of Escherichia coli growing on nutrient agar following irradihtion exhibited a slower growth than did colonies from non- irradiated cells. The retardation of growth was dose-dependent. (auth)