Heat tolerance mechanisms of an exceptional strain of Escherichia coli

Abstract

The mechanism of heat resistance in an exceptionally resistant strain of E. coli was investigated. E. coli AW1.7 was compared to a heat sensitive strain, E. coli GGG10. The heat resistance of both strains was increased by inclusion of NaCl, but only E. coli AW1.7 exhibited a consistent heat increase to resistance when growth in NaCl concentrations ranging from 2 to 6%. The quantification of cytoplasmic solutes in E. coli and the determination of thermal ribosome and protein denaturation demonstrated that ribosomes are more stable in E. coli AW1.7 than in E. coli GGG10. Ribosome stability and heat resistance corresponded to the accumulation of compatible solutes. Differences in protein denaturation between the strains were not observed. In conclusion, heat resistance in E. coli AW1.7 is dependent on solute transport. Knowledge on the mechanism of heat resistance of E. coli will facilitate the design of novel intervention methods to warrant food safety.