BACILLUS-THURINGIENSIS CONJUGATION UNDER ENVIRONMENTAL-CONDITIONS

A Bacillus thuringiensis plasmid carrying an insecticidal crystal prot ein gene (cry1Ac) was genetically marked with a gene conferring resist ance to erythromycin. The conjugative transfer of this plasmid between B. thuringiensis strains was analyzed in broth culture. soil microcos ms and infected larvae of the lepidopteran insect Anticarsia gemmatali s. Transconjugants appeared after 2 h in broth culture and after 4 h i n soil systems. The lowest conjugation frequency was in soil (8.0 x 10 (-8)-2.7 x 10(-5)) and the highest in infected larvae (1.0-8.4 x 10(-1 )). Plasmid transfer was observed in non-supplemented soils originatin g from sites with and without different plant covers. Thus non-amended soil and insect larvae appear to be favorable environments for plasmi d transfer by conjugation. (C) 1998 Federation of European Microbiolog ical Societies. Published by Elsevier Science B.V.