2-DIMENSIONAL ELECTROPHORESIS METHOD USED FOR DETERMINATION OF PLASMID PROFILES OF ESCHERICHIA-COLI ISOLATED FROM A SEWAGE-TREATMENT PLANT

The plasmid contents of 306 strains of Escherichia coli isolated from raw and treated sewage from a treatment plant as well as from the wate r 1 km downstream were determined. The number and molecular weight of plasmids isolated from a representative sample of these strains were a lso measured. It was observed that biological treatment did not signif icantly alter these parameters. In contrast, statistically significant differences in plasmid number and size were observed when strains fro m sewage (raw and treated) were compared with strains isolated from br ackish water. In raw and treated sewage, more than 96% of the strains contained plasmids, compared with 85% in brackish water. Nine to 13% o f the strains from sewage contained plasmids with more than 56 kilobas es, while only 5% of the strains from brackish water reached this size .