DISTRIBUTION OF UIDA GENE-SEQUENCES IN ESCHERICHIA-COLI ISOLATES IN WATER SOURCES AND COMPARISON WITH THE EXPRESSION OF BETA-GLUCURONIDASE ACTIVITY IN 4-METHYLUMBELLIFERYL-BETA-D-GLUCURONIDE MEDIA

The uidA gene, which encodes the beta-glucuronidase enzyme, was detect ed in 97.7% of 435 Escherichia coli isolates from treated and raw wate r sources by DNA-DNA hybridization; 92.4% of the strains expressed the translational product in 4-methylumbelliferyl-beta-D-glucuronide-cont aining media after reinoculation. Upon initial isolation from water sa mples, the minimal medium yranoside-4-methylum-belliferyl-beta-D-glucu ronide preparations failed to detect more than 50% of the E. coli isol ates that possessed uidA gene. Treated water gave the lowest recovery, with Colilert producing 26% positive samples and Coliquik producing 4 8% positive samples. There appears to be no relationship between the i ntensity of the autoradiographic signals of the uidA gene and the expr ession of beta-glucuronidase activity. Therefore, another variable suc h as physiological condition of the bacteria could be responsible for the nonexpression of the enzyme activity.