Histidine utilisation operon (hut) is upregulated at low temperature in the antarctic psychrotrophic bacterium Pseudomonas syringae.

The antarctic psychrotrophic bacterium Pseudomonas syringae was mutagenised using a transposon Tn5-OT182 which facilitates identification of promoter fusions expressing the reporter gene (lacZ) for beta-galactosidase. Most mutants expressed beta-galactosidase both at optimal growth temperature (20-22 degrees C) and at low temperature (4 degrees C). But a small percentage of the mutants (approximately 5%) were unique in that they expressed beta-galactosidase activity predominantly at low temperature. One such mutant was found to have an insertion in the gene for urocanase (hutU) of the histidine utilisation (hut) operon. Direct assay of urocanase and histidase activity in wild-type cells of various antarctic psychrotrophic strains including P. syringae, P. fluorescens and P. putida also suggested that the hut operon is expressed at an elevated level at low temperature.

De-emulsification of oil-in-water emulsions by Bacillus subtilis.

Bacillus subtilis grown on glucose produced a de-emulsifier that broke down model oil-in-water emulsions. The deemulsification increased with contact time and the recovery of oil was 98% with 0.6 mg de-emulsifier/ml emulsion. GLC and i.r. analysis of the molecule extracted from cell-free broth demonstrated that the de-emulsifier was acetoin. It may be better to use acetoin, a metabolite of glucose metabolism, to recover oil from oily sludges instead of microbial cells, because of its stability and de-emulsification activity.