SURVIVAL OF ESCHERICHIA-COLI K12 IN SEAWATER

The fate of an auxotrophic Escherichia coli K12 strain (NF1830) in coastal water was investigated. The E. coli K12 were enumerated after incubation for varying times in seawater. Incubated in raw seawater at 15 and 20-degrees-C, the NF1830 decreased from 10(6) cfu/ml to below detection within six days of incubation, but when incubated at 7-degrees-C it persisted longer. The NF1830 was capable of cell division in sterile seawater. Growth was also shown to occur in raw seawater in the presence of autoclaved sediment. The E. coli K12 decreased in number at a much lower rate when incubated in seawater treated with eukaryotic inhibitors. These findings suggest that the die-off of the auxotrophic E. coli K12 strain seen in the raw seawater was caused by grazing of bacterial predators in the seawater.