In situ survival of genetically engineered microorganisms in a tropical aquatic environment

In this study, the survival of genetically engineered microorganisms (GEMs) and their interactions with the environmental microbiota of a tropical river was investigated. Diffusion chambers were used for the in situ survival experiments with a nonplasmid containing Escherichia coli DH1 strain and two model GEMs, E. coli JM103 containing a 2.6 kilobase plasmid (pUCS) and E. coli DH1 with a 4.8 kb plasmid (pWTAla5'). Pure culture survival studies indicated that after a week in the environment a 1.0 log(10) decrease in bacterial numbers occurred for both E. coli DH1, while a 3.0 log(10) reduction was observed for E. coli JM103. However, a reduction of 4.0 log(10) was observed for the E. coli DH1 (pWTAla5') when placed in a chamber conjointly with the resident microbiota. The data suggest that the presence of a plasmid makes no difference on the survival time of GEMs, whereas the presence of competing bacteria is ultimately what limits the survival time of GEMs in the environment. (C) 1996 by John Wiley & Sons, Inc.