Application of bacterial predation to mitigate recombinant bacterial populations and their DNA

Abstract

Bdellovibrio bacteriovorus HD 100 is a bacterium that predates upon other gram negative bacterial strains. Using a fluorescent strain of Escherichia coil, we demonstrated that this predator can rapidly and significantly reduce recombinant bacterial populations within aqueous environments and soil slurries. Within aqueous environments, the E. coil populations were reduced by more than 7-log within 24 h. Predation within soil, however, was hampered by the soil particles, leading to little or no apparent loss in E. coil viable counts over 48 hours when the soil content was 40% (w/v) in water. However, a 5-log loss-in E. coli viability was seen when the soil quantity was only 1 g, i.e., 10% w/v. Using real-time qPCR and transformation assays, it was demonstrated that the plasmid copy number within the different samples was reduced by approximately 700-fold in aqueous samples and 170-fold in the presence of I g of soil. Furthermore, B. bacteriovorus predation under anoxic conditions was demonstrated for the first time in this study when nitrate was added to the medium, with a 90% reduction in colony forming units over 48 h. In conclusion, this study demonstrates the potential of applying bacterial predators, such as B. bacteriovorus, to quickly reduce recombinant bacterial populations that may have been accidentally released into nature and, hence, limit the chances for horizontal gene transfer between the recombinant strain and the native microflora.