INTERSPECIFIC TRANSFORMATION OF BACILLUS-SUBTILIS BY CLAY-BOUND DNA IN NONSTERILE SOIL

The interspecific transformation of Bacillus subtilis by both free and clay (montmorillonite)-bound DNA, isolated from B. amyloliquefaciens, B. cereus, B. licheniformis, B. polymyxa, B, pumilus and B. thuringie nsis, and from intergenotes obtained in the heterologous exchanges, wa s investigated in non-sterile soil conditions. Transformation by free heterologous DNA from all the species occurred at a very low frequency , with the exception of DNA from B. amyloliquefaciens. Intergenotic DN A was capable of transforming with a higher efficiency than heterologo us DNA, similar to that of the homologous DNA. Heterologous transforma tion by clay-DNA complexes was obtained only with DNA from B. amyloliq uefaciens, while intergenotic DNA bound on clay transformed at a frequ ency about one-two orders of magnitude lower than homologous DNA. Tran sformation frequency in non-sterile soil was similar to that obtained in the absence of nonsterile soil. The genetic distances among the Bac illus species and the intergenotes were determined by the random ampli fied polymorphic DNA (RAPD) fingerprinting technique. The results show that B. subtilis is very similar to the intergenotes and B. amyloliqu efaciens and more distant from the other Bacillus species.