Fig. 1

def cannot be deleted from wt M. smegmatis. On the right, colonies after a confirmed second recombination event were checked by PCR to differentiate def-deletion (resulting in 1.2 kb product) from reversal to wt (1.8 kb fragment). 13 colonies are shown, out of 60 examined. On the left – wt control, and a true Δdef mutant (obtained as described in section 3.2)