The rpoH gene, encoding the heat shock protein transcription factor sigma(32), was obtained by PCR and cloned into plasmid pUHE with the tac promoter. Upon induction with IPTG, it directed the expression of sigma(32) tailed with six additional histidine residues at its C-terminus. The histidine-tagged sigma(32) was purified with nickel-iminodiacetic acid affinity chromatography. Using (35)S radiolabeling methods in vivo, we found that even at low temperature the expression of sigma(32)-6 His may markedly increase the synthesis of the heat shock proteins such as GroEL, Dnak, and HtpH.