THE AGGREGATION-MEDIATED CONJUGATION SYSTEM OF BACILLUS-THURINGIENSISSUBSP. ISRAELENSIS - HOST-RANGE AND KINETICS OF TRANSFER

The aggregation-mediated conjugation system in Bacillus thuringiensis subsp. israelensis encoded on the plasmid pXO16 is characterized by th e formation of aggregates when Agr(+) and Agr(-) cells are socialized in exponential growth. Using the aggregation phenotypes, we have ident ified potential recipients of the aggregation-plasmid pXO16 among Baci llus cereus, Bacillus subtilis, Bacillus megaterium Bacillus sphaericu s, and 24 subspecies of B. thuringiensis. We found 14 Agr(-) strains, i.e., potential recipients of the aggregation system encoded by plasmi d pXO16. Five strains contained a conjugative apparatus of their own a nd were excluded from further examinations. To monitor the transfer of plasmid pXO16, we constructed a transposon insertion of the plasmid w ith Tn5401. The study of the plasmid transfer of pX016::Tn5401 indicat ed the secretion of bacteriocins from both donor strain and recipient strains. Only one out of the nine strains examined was unable to recei ve the aggregation-plasmid pXO16 and express the aggregation phenotype and the conjugative abilities. It was found that the transfer of plas mid pX016 to Bacillus thuringiensis subsp. israelensis Agr(-) strains was 100%. All recipients had acquired the aggregation-plasmid pXO16 an d converted to the Agr(+) phenotype.