THE RECOVERY OF HEAT-STRESSED ESCHERICHIA-COLI IN LAKE WATER MICROCOSMS

Escherichia coli was heat stressed at 55 degrees, 60 degrees or 65 degrees C in sterile flasks of lake water. After 6 h at these temperatures the viable count on nutrient agar had dropped below the limits of detection (1 colony in 100 mi). The flasks were transferred to a 15 degrees C incubator and left for 7 d. Recovery of the stressed E. coli was shown to occur within 48 h at this temperature. Recovery also occurred in microcosms amended with 5% (v/v) synthetic sewage. The stressed E, coli multiplied in the amended but not in the unamended microcosms.