Fig 3. Levels of ß-galactosidase from recA-lacZ with and without DNA damage during sporulation in SOS-proficient (a and b) and –deficient (c and d) B. subtilis strains.

B. subtilis strains LAS600 (parental) and LAS523 (SOS-deficient) containing a recA-lacZ fusion were grown and induced to sporulate in DSM. The optical densities of cultures were measured without (○) or after (●) DNA damaging treatment. 4 h after the onset of sporulation (T₀), the culture was divided into two subcultures; one subculture was challenged with M-C (500 ng/mL) and the other one was untreated. Cells samples from untreated (open symbols) or treated (filled symbols) were collected at the indicated times and ß-galactosidase specific activity in the mother cell (a and c, triangles) and forespore (b and d, squares) fractions was determined, all as described in Materials and Methods.