Effects of sublethal temperature stresses on the culturability and morphology of Escherichia colia

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.