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

Chromosomal DNA from Bacillus subtilis and different forms of plasmid pHV14 (covarently closed circular (CCC), linear monomer (M), and linea r multimer (LM)) were adsorbed and bound on the clay mineral montmoril lonite. After extensive washing of the clay-DNA complexes with DNA buf fer (pH 7.5), approx. 25% of the chromosomal DNA, and approx. 30, 90, and 5%, respectively, of the CCC, M and LM form remained bound. Chromo somal and plasmid DNA bound on clay were capable of transforming compe tent cells, with different specific activities. The clay-DNA complexes persisted in non-sterile soil and retained transforming ability up to 15 days after their addition to the soil. DNA bound on montmortilloni te was protected from the activity of EcoRI, supporting the evidence t hat DNA adsorbed on soil components was resistant to degradation by nu cleases.