Release of extracellular transformable plasmid DNA from Escherichia coli cocultivated with algae

We studied the effects of cocultivation with either Euglena gracilis (Euglenophyta), Microeystis aeruginosa (Cyanophyta), Chlamydomonas neglecta (Chlorophyta), or Carteria inversa (Chlorophyta) on the production of extracellular plasmid DNA by Escherichia coli LE392(pKZ105). Dot,blot hybridization analysis showed a significant release of plasmid DNA by cocultivation with all the algae tested. Further analysis by electrotransformation confirmed the release of transformable plasmid DNA by cocultivation with either E. gracilis, M. aeruginosa, or C. inversa. These results suggest algal involvement in bacterial horizontal gene transfer by stimulating the release of transformable DNA into aquatic environments.