Bacterial Persistence in Aquatic Environments: A Study of Green Fluorescent Protein (GFP)-Tagged Escherichia coli in Laboratory Microcosms

Background and Objective: In-depth knowledge of survival potential and survival patterns of wild-type and genetically engineered E. coli in aquatic systems is scarce. The study was designed to investigate the relative persistence and survival of transformed E. coli DH5α and environmental isolates. Materials and Methods: Three different types of microcosms were set up and inoculated with GFP-transformed E. coli. Samples were collected at regular intervals and the survival and growth of the organisms were monitored by viable counts using GFP as a cellular marker. Survival curves were prepared to visualize bacterial persistence trends over time. Results: The obtained results suggested different survival patterns of E. coli in different microcosms. The survival of E. coli in filter-sterilized water samples was found greater than that in untreated water. A sharp decrease in the count of E. coli cells in untreated water, compared to that of filter-treated and/or autoclaved water suggests that the survival of E. coli in natural water might be limited due to deprivation of nutrients or biological interactions, such as competition and predation. Conclusion: Transformation of GFP in E. coli did not show a significant effect on the persistence in the laboratory microcosm underscoring the potential utility of GFP-tagged E. coli as a model organism for studying bacterial survival and distribution dynamics.