Binding of DNA from Bacillus subtilis on montmorillonite-humic acids-aluminum or iron hydroxypolymers:: Effects on transformation and protection against DNase

The equilibrium adsorption and binding of DNA from Bacillus subtilis on complexes of montmorillonite-humic acids Al or Fe hydroxypolymers (Al-M-HA or Fe-M-HA) at different M/HA ratios, the desorption of DNA, the capacity of bound DNA to transform competent cells of B. subtilis in vitro, and the protection of bound DNA from degradation by free and organomineral-bound DNase I are reported. Adsorption was rapid (maximal after 2 h), occurred from pH 3 to 10, and was higher on Al-M-HA than on Fe-M-HA. Saturation of the sites on the surface or between the layers of Al- or Fe-M-HA occurred with only some complexes, depending on how the complexes were prepared. Essentially no desorption under stringent conditions was observed. Bound DNA transformed auxotrophic competent cells of B. subtilis, although at a lower frequency than free DNA. Bound DNA was protected more than free DNA against degradation by DNase I, and differences in resistance to degradation between free and bound DNA were more evident when DNase was also bound on the organomineral complexes.