Coexistence of genetically engineered Escherichia coli strains and natural microorganisms in experimental aquatic microcosms

In experimental aquatic microcosms (AMCs), the population of the Escherichia coli strain Z905 harboring the recombinant plasmid pPHL7 (Ap(r)Lux(+)) was found to gradually accumulate AMC-adapted cells, which retained the plasmid but differed from the original cells in some biochemical and physiological characteristics. Both the original and the AMC-adapted E. coli cells could coexist with the native AMC microflora for one year or longer. When introduced into AMCs together with native pseudomonads, the AMC-adapted E. coli Z905-33 (pPHL7) cells were more competitive than the nonadapted cells.