Influence of a Survival Process in a Freshwater System upon Plasmid Transfer Between Escherichia coli Strains

Abstract

Survival and potential ability to act as recipient or donor during the survival process for one plasmid-free and four plasmid-bearing Escherichia coli strains under nonilluminated and illuminated conditions in freshwater systems were studied. The five E. coli strains showed the same behavior with respect to the microbial parameters used to characterize the survival process (culturability and viability). Under nonilluminated conditions, recipient cells did not show variation in the ability to receive and express plasmid material, while the culturability of the recipient strain remained stable. Under the same conditions, donor cells lost their ability for plasmid transfer during the survival process, in all cases more than a 90% decrease of the number of transconjugants was found after 4 days of experimentation, although viable and culturable cells of donor strains maintained the capacity to express some plasmidic genes. Under illuminated conditions, transconjugants were not detected after 2 days of experimentation. The number of transconjugants formed was dependent not only on the time donor strains remained in the water but also on the temperature (20 or 37°C) at which the mating assays were conducted.