Determinants of heat resistance in Escherichia coli AW1.7

Microarray hybridization of cDNA libraries obtained from exponentially growing or heat-shocked AW1.7 or GGG10 cultures was performed to compare gene expression of these two strains. Expression of selected genes from different functional groups was quantified by quantitative PCR (q-PCR). DnaK, 30S and 50S risobomal subunits were overexpressed in E. coli GGG10 relative to E. coli AW1.7 upon heat shock at 50°C, indicating improved ribosome stability. The outer membrane porin NmpC and several transport proteins were overexpressed in exponentially growing E. coli AW1.7. Gene expression of a heat resistant strain, E. coli AW1.7, was compared to gene expression in a heat sensitive strain, E coli GGG10. RNA was isolated from late exponential cultures, or from late exponential cells heat-shocked by exposure to 50°C for 15 min. Three independent biological repeats were analyzed, and technical repeats (dye-swap) were performed for two of three biological repeats.