A BIOCHEMICAL, BASIS FOR APPARENT ABORTIVE TRANSFOfiMATION IN BACZLLUS SUBTZLZSl

mutant derivative that was reported to undergo unstable DNA transformaA tion (abortive transformation) was previously isolated from a transformable strain of Bacillus subtilis (IYER 1965). In view of the fact that such a system of abortive transformation would be a powerful and much needed tool for analyzing dominance relationships of genes in B. subtilis, we report the experimental basis of our conclusion that the behavior of the strain derives from nutritional interactions that depend upon the specific biochemical lesions carried by the mutant. The mutant strains proved to possess a previously undetected biochemical block in the histidine pathway. The latter mutation correlated with the ability of competent cells to interact with transforming DNA from wild-type donors to produce minute colony recombinants (abortive transformants). The biochemical block constitutes a trivial explanation for the apparent abortive transformation that is simulated under a limited set of nutritional conditions.