STABILITY OF PLASMID-BORNE RESISTANCE OF ANTIBIOTICS DURING STARVATION OF ESCHERICHIA-COLI IN RAW AND TREATED WASTE-WATER AND BRACKISH-WATER

Cell survival and plasmid stability in Escherichia coli containing pla smids RP1, R388 and pUB824 were studied in raw waste water, treated wa ste water, and brackish water. The Escherichia coli strain survived we ll in raw and treated waste water. However, in brackish water E. coli HB101 remained culturable throughout the microcosm study, with an over all drop of 2 log units in culturability from the start to the end of the experiment, The maintenance of the three plasmids was plasmid-, an d environment-dependent. Plasmid pUB824 (4 kb) was stably maintained u nder all conditions used in the study. Maintenance of RP1 (56 kb) and R388 (33 kb) was markedly influenced by nutritive conditions, which ca used a segregation of the plasmids from cells. The results of the pres ent study demonstrate the influence of plasmid size on plasmid stabili ty in natural waters.