FIG. 4.

The cell fate determinants SinR and RapA are responsible for the inhibition of spore morphogenesis under alcohol stress. Levels of Spo0A∼P-dependent β-galactosidase activity from different JH16304-derived isogenic strains harboring rapA and/or sinR mutations in the presence or absence of ethanol (black and white bars, respectively). Cultures of JH16304 (wild type) and the isogenic derivatives RG1400 (ΔrapA::ery), RG1401 (ΔsinR::cat), and RG1402 (ΔrapA::ery ΔsinR::cat) were grown in SSM until the late exponential phase (T_−1.5), when ethanol (0.7 M) was added to one-half of each culture. Growth of the eight cultures was continued for several hours, and samples were collected and assayed for β-galactosidase activity. The reported Miller units (M.U.) represent the sum of β-galactosidase activities determined every 30 min from T₀ to T_2.5 for each culture. Data are the averages from three independent experiments done in triplicate. The activity of the Spo0A reporter lacZ fusion and the efficiency of spore formation (+/− ethanol) were essentially the same for strains RG19 (rapA::mini-Tn10-Spc^r)/RG1401 (ΔrapA::Ery^r) and RG23 (ΔsinR::mini-Tn10-Spc^r)/RG1400 (ΔsinR::Cat^r), respectively (data not shown).