RecO, RecU, and Ku play an important role in plasmid transformation, but are dispensable for transformation with chromosomal DNA.

Competent B. subtilis cells auxotrophic for methionine were transformed with chromosomal DNA from a met+ (SB19) strain. The yield of met+ transformants (chromosomal transformation), kanamycin-resistant transformants (plasmid pUB110 transformation), and SPP1 transfection was corrected for DNA uptake and cell viability and the values obtained normalized relative to that of the rec+ strain, taken as 100 (between parentheses, the number of transformants/transfectants obtained per 0.1 µg DNA/ml). The results are the average of at least five independent experiments and are within a 10% standard error.