Transforming activity of mercury-substituted DNA synthesized in vitro by permeable cells of Bacillus subtilis

Mercurated DNA was synthesized in permeable cells of Bacillus subtilis, using 5-mercurideoxycytidine triphosphate as one of the substrates, and was separated from parental unsubstituted DNA by isopycnic centrifugation in CsCl gradients. The ability of mercurated DNA to transform auxotrophic strains of B. subtilis to prototrophy was compared with that of normal DNA and was 10-20% of the latter. Mercurated and normal DNA bound with similar affinities to identical surface receptors of the recipient cells, but the efficiency of the bound mercurated DNA in promoting transformation was one-tenth to one-fifth of that of normal DNA. The transforming activity of mercury-substituted DNA synthesized in an in vitro system opens the way for the use of mercury as a probe to study the mechanism of bacterial transformation and various other kinds of genetic exchange.