| Abstract |
The conjugative transfer ranges of three different plasmids of the incompatibility groups IncP-1 (pBP136), P-7 (pCAR1), and P-9 (NAH7) were investigated in soil bacterial communities by culture-dependent and culture-independent methods. Pseudomonas putida, a donor of each plasmid, was mated with soi .. [more]l bacteria and a green fluorescent protein (GFP), encoded on the plasmid, was used as a reporter protein for successful transfer. GFP-expressing transconjugants were detected and separated at the single-cell level by flow cytometry. Each cell was then analyzed by PCR and sequencing its 16S rRNA gene following either whole genome amplification or cultivation. A large number of bacteria within the phylum Proteobacteria was identified as transconjugants for pBP136 by both culture-dependent and culture-independent methods. Transconjugants belonging to the phyla, Actinobacteria, Bacteroidetes, and Firmicutes, were detected only by the culture-independent method. Genus Pseudomonas (class Gammaproteobacteria) was identified as major transconjugants of pCAR1 and NAH7 by both methods, whereas Delftia species (class Betaproteobacteria) were detected only by the culture-independent method. The transconjugants represented a minority of the soil bacteria. Although pCAR1-containing Delftia strains could not be cultivated after a one-to-one filter mating assay between the donor and cultivable Delftia as recipients, fluorescence in situ hybridization detected pCAR1-containing Delftia cells, suggesting that Delftia was a ‘transient’ host of pCAR1. [less]
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FTP
