Bacillus thuringiensis conjugation under environmental conditions

A <it>Bacillus thuringiensis</it> plasmid carrying an insecticidal crystal protein gene (<it>cry</it>1Ac) was genetically marked with a gene conferring resistance to erythromycin. The conjugative transfer of this plasmid between <it>B. thuringiensis</it> strains was analyzed in broth culture, soil microcosms and infected larvae of the lepidopteran insect <it>Anticarsia gemmatalis</it>. Transconjugants appeared after 2 h in broth culture and after 4 h in soil systems. The lowest conjugation frequency was in soil (8.0×10−8–2.7×10−5) and the highest in infected larvae (1.0–8.4×10−1). Plasmid transfer was observed in non-supplemented soils originating from sites with and without different plant covers. Thus non-amended soil and insect larvae appear to be favorable environments for plasmid transfer by conjugation.