Mobilizable bacterial DNA packaged into membrane vesicles induces serial transduction.

Experiments where the amino acid deficient strain E. coli AB1157 was exposed to a particle fraction harvested from a marine oligotrophic environment, ranging in diameter size between 100-130 nm indicated evidence for horizontal gene transfer resulting in revertant cells with restoration of all genetic deficiencies with frequencies up to 1.94 × 10(-5). None of the markers was preferentially transferred indicating that the DNA-transfer is performed by generalized transduction. The highest transfer frequency obtained for single markers was 1.04 × 10(-2). All revertant strains were able to produce particles of comparable size that were again infectious, appearing at the beginning of the stationary phase. Ultra structural investigation showed a structural resemblance with membrane vesicles, however, Field Gel Electrophoresis indicated that the DNA content of some of the particles was 370 kbp; much higher than that of the so far known previously described membrane vesicles providing evidence of a new mechanism for horizontal gene transfer.