Interspecific transformation of Bacillus subtilis by clay-bound DNA in non-sterile 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. thuringiensis, and from intergenotes obtained in the heterologous exchanges, was 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. arayloliquefaciens. Intergenotic DNA was capable of transforming with a higher efficiency than heterologous DNA, similar to that of the homologous DNA. Heterologous transformation by clay-DNA complexes was obtained only with DNA from B. amyloliquefaciens, while intergenotic DNA bound on clay transformed at a frequency about one-two orders of magnitude lower than homologous DNA. Transformation frequency in non-sterile soil was similar to that obtained in the absence of nonsterile soil. The genetic distances among the Bacillus species and the intergenotes were determined by the random amplified polymorphic DNA (RAPD) fingerprinting technique. The results show that B. subtilis is very similar to the intergenotes and B. amyloliquefaciens and more distant from the other Bacillus species.