TEMPERATURE SHIFT-UP LEADS TO SIMULTANEOUS AND CONTINUOUS PLASMID DNARELAXATION AND INDUCTION OF DNAK AND GROEL PROTEINS IN ANAEROBICALLY GROWING ESCHERICHIA-COLI-CELLS

We previously reported that plasmid DNA in Escherichia coli cells grow ing under aerobic conditions relaxed immediately and transiently after heat shock (Mizushima, T., Natori, S. and Sekimizu, K., Mel, Gen. Gen et. (1993) 235, 1-5). We next examined DNA relaxation and induction of heat shock proteins after heat shock in cells growing under anaerobic conditions. DNA in these cells relaxed rapidly (2 min) after heat sho ck (42 degrees C), as was the case with aerobically growing cells, but full superhelicity was not recovered. The relaxed state of DNA topolo gy was maintained for 60 min after heat shock. Induction of DnaK and G roEL proteins, which was transient in aerobically growing cells, was c ontinuous in anaerobically growing cells. Therefore, induction of heat shock proteins correlated with DNA relaxation in both aerobic and ana erobic conditions.