Direction of DNA entry in competent cells of Bacillus subtilis

Direction of DNA entry in Bacillus subtilis competent cells was studied using molecules in which only one of the two strands was radioactively labelled. The label was either distributed homogeneously or was localized in a small region of the strand, in the centre or at one of the ends. Regardless of the distribution and the position of the label, similar amounts of radioactivity were taken up by the cells exposed to the labelled molecules. This suggests that DNA enters B. subtilis either by two different uptake systems having opposite polarities, or by a single non-polar system.