Biological assay of prokaryotic genes in mouse cells following DNA mediated transformation

Genes coding for leucine biosynthesis in Bacillus subtilis were introduced into mouse LTK- cells by co-transformation with thymidine kinase+ (tk) DNA. Genomic DNA from the tk+ transformants was used to transform competent cultures of different B. subtilis leucine auxotrophs. Each auxotroph was transformed to prototrophy at a similar frequency and the number of leucine gene sequences per transformant genome as deduced by the B. subtilis bioassay strongly correlated with the number estimated by hybridization methods. Tk- subclones were obtained by plating the transformants in 5'-bromodeoxyuridine. One subclone still contained the non-selected leucine gene sequences and could transform auxotrophs of B. subtilis. No deletions or rearrangements in the linkage relationships of the leucine genes occurred in the LTK- cells that inhibited transformation of B. subtilis.