SOS induction assay. (A) Kinetics of yneA-lacZ induction. Aliquots of the YNEAd culture treated with (closed squares) or without (open squares) mitomycin C were withdrawn 20 (lane 1), 40 (lane 2), and 60 (lane 3) min after drug treatment and assayed for β-galactosidase activity. Portions of an alternatively grown NBS218 culture, a triple-RNase H-deficient strain, were sampled (open circles) as described in Materials and Methods and assayed for β-galactosidase activity. (B) Effects of yneA deletion on B. subtilis cell morphology. Cells from exponentially growing cultures were examined under a microscope. (a) 168 (wild type). (b) Triple-RNase H-deficient strain NBS210. (c) Triple-RNase H- and yneA-deficient strain NBS218. Bar, 10 μm.