Effects of the growth conditions on expression of comX and cellular levels of MecA, ClpC and ClpP. A. Luciferase reporter activities (black circles and triangles) of the competence-specific promoter, PcomX, in S. mutans strain XT-Lx1 grown in THYE (open circles) or in CDM (open triangles) in response to CSP or XIP. B. Western blot analysis of cellular levels of MecA, ClpC or ClpP in S. mutans strains GF-His2 (MecA-His), GF-His3 (ClpC-His) and GF-His4 (ClpP-His) grown in THYE (+CSP) and in CDM (+XIP). The samples were taken from the cultures of these strains during the early- (E), mid- (M) and late- (L) exponential phases to prepare the crude cell lysates. The MecA, ClpC and ClpP were detected by Western blotting using the anti-His antibody, while the protein loading controls were detected using the anti-S. mutans antibody.