Comparison of the direct enzyme assay method with the membrane filtration technique in the quantification and monitoring of microbial indicator organisms – seasonal variations in the activities of coliforms and E. coli, temperature and pH

Abstract

The aim of this project was to monitor variations and relationships between coliform and E. coli counts, the activities of their marker enzymes GAL and GUD, and temperature and pH over a period of 12 months in river samples obtained from the Eastern Cape, South Africa. Several polluted water samples were collected for direct coliform β-D-galactosidase (B-GAL) and Escherichia coli β-D-glucuronidase (B-GUD) assays and the membrane filtration technique. While all the samples showed enzyme activities, not all exhibited growth on CM1046 media. Variation in B-GAL activity (40%) was observed between November (highest activity month) and May (lowest activity month). The highest and lowest B-GUD activities were observed in the months of September and May/June, respectively. The sensitivity of the spectrophotometric assay method was indi cated by a limit of detection (LOD) of 1 coliform forming unit (CFU)/100 mℓ and 2 CFU/100 mℓ for coliforms and E. coli, respectively. There was a significant (P < 0.05) positive correlation between E. coli counts and GUD activity (R 2 = 0.8909).

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