Growth of Escherichia coli at elevated temperatures

In our studies to develop a simple and reliable method for the generation of recombinant adenoviruses (Fotadar et al . 2003), we noted that the E. coli (BJ5183 and DH5alpha) survived a heat-shock of 45 degrees C for 5 minutes in 0.1 M calcium chloride. As a result, we investigated the growth of E. coli (DH5alpha) at elevated temperatures. We hereby demonstrate that contrary to previous observations (Cooper et al . 2001 and Bronikowski et al . 2001) E. coli can grow consistently at a temperature as high as 49 degrees C, in spite of the fact that growth beyond 40 degrees C can generally be prohibitive. Hence, it is quite likely that these E. coli (DH5alpha) may have acquired mutations which permit them to grow reproducibly at 49 degrees C. Growth of E. coli above 49 degrees C (up to 53 degrees C) was also observed, but this was sporadic and not reproducible. This result could extend the utility of these organisms for cloning and manipulations requiring high temperature.