The influence of earthworms on gene transfer in the environment

A model system to assess the influence of earthworm activity on transfer of pJP4 between: (1) a surface inoculated donor bacterium, Pseudomonas fluorescens to indigenous soil microorganisms, and (2) spatially-separated donor (Alcaligenes eutrophus) and recipient (Pseudomonas fluorescens) bacteria in nonsterile 40-cm soil columns. Three different earthworm species (Aporrectodea trapezoides, Lumbricus rubellus, and Lumbricus terrestris), each with unique behaviors, were evaluated. Inoculated soil microcosms were analyzed for donor, recipient and transconjugant bacteria at 5-cm-depth intervals.;In both studies, the presence of earthworms significantly increased dispersal of inoculated strains. In situ gene transfer of pJP4 from P. fluorescens to indigenous soil bacteria was detected in all inoculated microcosms. However, the total number of transconjugants recovered from soil was significantly greater in microcosms containing either L. rubellus or A. trapezoides, with levels reaching 10;Donor and transconjugant bacteria were also recovered from earthworm casts and inside developing cocoons when P. fluorescens (pJP4) was inoculated into earthworm-containing microcosms. Numbers of transconjugants reached up to 10...