Use of enzymatic methods for rapid enumeration of coliforms in freshwaters

Rapid enumeration methods based on the enzymatic hydrolysis of 4-methylumbe lliferyl-beta-d-galactoside and 4-methylumbelliferyl-beta-d-glucuronide wer e optimized for freshwaters. The enzymes beta-d-galactosidase (GALase) and beta-d-glucuronidase (GLUase) were shown to be already induced in freshwate rs when tested, respectively, with the inducers isopropyl-beta-d-thiogalact opyranoside and methyl-beta-d-glucuronide. Both enzymatic activities were c ompared, respectively, with plate counts of total and faecal coliforms in f reshwaters. Enzymatic methods and reference plate counts were significantly correlated in log-log plots. Moreover, the GLUase method allowed the detec tion of viable (presenting a detectable GLUase activity) but nonculturable Escherichia coli.