Fate of plasmid-bearing, luciferase marker gene tagged bacteria after feeding to the soil microarthropod Onychiurus fimatus (Collembola)

In order to study the potential impact of the soil microarthropod Onychiuru s fimatus (Collembola) on the microbial community, we analysed the fate of luciferase marker gene tagged bacterial strains fed to young adult specimen s in petri dish microcosm experiments. In farces collected from O. fimatus, Escherichia coil S17-1/pRP4luc and Sinorhizobium meliloti L33 were only de tectable for 2 days after feeding whereas strain HR2/pRP4luc, a close relat ive of Stenotrophomonas maltophilia, isolated from another collembolan spec ies, could be detected for 16 days. The amount of shed cells of strain HR2 increased during the frequent releases of the cast-off skins (exuvia). In o rder to analyse whether gut associated bacteria could serve as recipients f or mobile genetic elements, plasmid-bearing E. coli donor strains were incu bated with faeces in filter mating-like experiments and, in other experimen ts, directly fed to O. fimatus specimens. Transconjugants were obtained wit h both the conjugative self-transferable broad host range plasmid pRP4luc a nd the mobilisable (Mob(+)) broad host range plasmid pSUP104luc, the latter , however, only with a mobilising donor strain. No transfer was detected wi th the narrow host range plasmids pSUP202luc (Mob(+)), pUC18luc (Mob(-)), o r with the broad host range transposon delivery plasmid pUTluxCDABE (Mob(+) ). Transconjugants of pRP4luc were detected within one day of the beginning of a feeding experiment and then throughout the incubation period of two w eeks, with gaps of no detection after 5, 12 and 14 days, probably caused by moulting. The results of this study indicate that Feeding activities of co llembola can modify the structure of soil-inhabiting microbial communities and enhance the spread of plasmids from non-indigenous to indigenous soil b acteria. (C) 1999 Federation of European Microbiological Societies. Publish ed by Elsevier Science B.V. All rights reserved.