Abstract
The psychrophilic bacterium, Colwellia maris, grows at low temperatures (5-15oC). Although groESL and dnaK genes of this bacterium are expressed at 20oC, their promoter regions are similar to the heat shock promoter of E. coli. To reveal specific mechanisms of heat shock response in psychrophiles, we cloned the rpoH gene and investigated its expression.
Using mixed oligonucleotides primers designed from conserved amino acid sequences in several RpoH, a partial fragment of the rpoH gene was obtained. Its deduced amino acid sequence showed 64% identity to the corresponding region of E.coli RpoH. The RpoH box, which is specific to RpoH, was identified in this DNA fragment. Northern blot analysis showed that the level of rpoH transcript reached the maximum level when treated at 20oC and that the rate of degradation was much slower at 20oC than at 10oC. These observations suggest that rpoH mRNA stability contribute to RpoH regulatrion.
