Analysis of gene transfer and expression mechanisms in aquatic ecosystems using the Aquatron

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Operational conditions for replicable aquatrons were clarified. Blooms of cyanobacterium Microcystis aeruginosa was induced artificially in the aquatrons. In these aquatrons, gene transfer of pT7GFP from E.coli (pT7GFP) to 0.1 to 0.8% of indigenous bacteria was detected within 3 to 5 days, by means of FISH targeted to pT7GFP couple with fluorescent antibody method. It was also found that extracellular metabolic products enhanced conjugal gene transfer of pBHR1 from E.coli S17-1(pBHR1) to Pseudomonas stutzeri.E.coli with a plasmid coding GFP gene was exposed to autolysis, infection of phage and predation by protozoa. Quantification of dissolved DNA, as gene source in a natural aquatic environments, in the treated sample, revealed that dissolved DNA from autolysis and infection of phage are likely to more contribute than the other to horizontal gene transfer among bacteria.Bacillus strains isolated from 17 various sites in the world possessed identical mer operon on similar transposons. This finding suggested that transposons may contribute the worldwide distribution and horizontal dissemination of the mer operons among Bacillus strains in natural environments. E.coli DH5α was incorporated with both a transposon, which was isolated from natural environment, on untransformable pGEM and transformable plasmid pR388. The transposon in the E.coli DH5α was transferred to E.coli S17-1 by conjugation. These experiments indicated that there existed transposition of the transposon from pGEM to pR388 in a cell.