Microcalorimetric method and DNA deletion mutagenesis technique were combined to study a putative gene promoter fragment (RM10) from the extremely halophilic archaea, Halobacteria halbium R1, for its promoter function toward Escherichia coli. The promoter fragments were fused to the promoter-less chloramphenicol acetyltransferase (CAT) gene on plasmid pKK232-8 to evaluate its ability of driving CAT gene expression. Deletion analysis for RM10 was performed to identify important functional region responsible for promoter activity toward Escherichia coli. From the view of thermokinetics, the experimental results revealed that the 1382 to 1517 bp (base pair) with the typical －35 and －10 box sequences of bacterial promoters was very critical region for promoter function to Escherichia coli, and there was a negative control region from 1 to 1382 bp or from 1571 to 1848 bp. Our research work also provided a very sensitive and easily-performed novel method, combining the chemical and biological technique, for studying gene promoter function.

Key words: microcalorimetry, halophilic archaea, deletion mutagenesis, gene promoter