Abstract:
This research was conducted in order to study the effects of sub lethal temperature stresses
on the culturability and morphology of Escherichia coli. The growth curve of E. coli was
established by using agitated and static cultivation methods. Since the results of both
cultivation methods were not significantly different, the static cultivation method was
chosen to carry on this research. E. coli was grown in Tryptone Soya Broth (TSB) at 37°C
using static cultivation method prior to shifting the bacterium to three sublethal
temperature stresses (20°C, 40°C and 45°C) at log and stationary phases. This study also
determined percentage injury for E. coli after exposure to sublethal temperature stresses.
The percentage injury of E. coli was highest after shifting temperature of 37°C to 45°C
compared to shifting temperature from 37°C to 20°C and 45°C. Results from this research
also showed that population growth at stationary phase was more resistance compared to
log phase at both temperature 40°C and 45°C but at 20°C the susceptibility of E. coli was
higher at stationary phase compare to log phase. For the observation of morphological
changes, it was concluded that the cells shape of E. coli at log phase for three sublethal
temperatures were more susceptible than at stationary phase.
