HISTIDINE UTILIZATION OPERON (HUT) IS UP-REGULATED AT LOW-TEMPERATUREIN THE ANTARCTIC PSYCHROTROPHIC BACTERIUM PSEUDOMONAS-SYRINGAE

The antarctic psychrotrophic bacterium Pseudomonas syringae was mutage nised using a transposon Tn5-OT182 which facilitates identification of promoter fusions expressing the reporter gene (lacZ) for beta-galacto sidase. Most mutants expressed beta-galactosidase both at optimal grow th temperature (20-22 degrees C) and at low temperature (4 degrees C). But a small percentage of the mutants (similar to 5%) were unique in that they expressed beta-galactosidase activity predominantly at low t emperature. One such mutant was found to have an insertion in the gene for urocanase (hutU) of the histidine utilisation (hut) operon. Direc t assay of urocanase and histidase activity in wild-type cells of vari ous antarctic psychrotrophic strains including P. syringae, P. fluores cens and P. putida also suggested that the hut operon is expressed at an elevated level at low temperature. (C) 1998 Published by Elsevier S cience B.V.