FIG. 7.

Western immunoblots showing ComD expression in whole-cell bacterial lysates taken from cultures of increasing cell density for (A) strain P1374 (wt) versus strain P1373 (htrA_S234A) and (B) strain P1374 versus strain P1359 (ΔcomAB). Each lane was loaded with 8 μg total protein. Samples were taken when the culture reached an OD₆₂₀ of 0.020 to 0.025 (t = 1), 0.070 to 0.074 (t = 2), 0.137 to 0.160 (t = 3), and 0.540 to 0.558 (t = 4). The cultures of P1373 and P1374 displayed spontaneous competence at the second and third time points, whereas that of P1359 did not exhibit competence (data not shown).