Plasmid transfer between introduced and indigenous bacteria in leaf litter, soil and vermicompost as affected by soil invertebrates

Abstract

Plasmid transfer between introduced strains of Pseudomonas stutzeri JM302 (pLV1013), Pseudomonas putida PAW340 (pLV1017), Pseudomonas aeruginosa PAO5 (RP4), and Enterobacter cloacae MF10 (RP4), all of them harbouring genetically modified or naturally occurring plasmids and bacteria indigenous to oak leaf litter, soddy-podzolic soil or vermicompost was monitored using non-sterile laboratory microcosms inhabited by the millipede Pachyiulus flavipes, the woodlouse Armadillidium vulgare, or the earthworms Aporrectodea caliginosa and Eisenia fetida, respectively. Plasmid transfer from genetically modified Streptococcus faecalis JH2-2 (pAMβ1) to Bacillus thuringiensis var. israelensis 1-5 under similar conditions was also followed. A recombinant conjugative plasmid (pLV1017) encoding resistance to antibiotics and expressing catechol 2,3-dioxygenase was transferred into two facultatively anaerobic gram-negative bacteria, isolated from the excrement of A. vulgare. Presumed transconjugants of the facultatively anerobic gram-negative bacteria given above were isolated from the leaves and soil (four strains) and the excrement of the invertebrates (11 strains). They carried the same plasmids and exhibited the same enzymatic activity as the respective inoculant strains; for most of them, however, DNA fingerprints were slightly different. Transfer from S. faecalis JH2-2 to B. thuringiensis var. israelensis of a naturally occurring plasmid, pAMb1, encoding resistance to erythromycin was observed in vermicompost.