Structure-function analysis of the signaling peptides. (A) Western blot detection of overnight CPB production by TGY cultures of the CN3685 and CN1795 agrB gene null mutants after activation by 100 μM concentrations of AgrD sequence-based peptides (5-R and 5-L) or variant peptides (5-RCS, 5-LCV, Ca5c, 6-L, and 6-R). A 6-mer random sequence peptide (6Ctrl) was used as a negative control. (B) CPB production by overnight TGY cultures of the CN3685 agrB null mutant and the CN1795 agrB null mutant after treatment with 100 μM concentrations of 5-R, 5-L, 5-RCS, 5-LCS, 5-LCV, Ca5c. A similar concentration of a 5-mer random sequence peptide (5Ctrl) was used as a negative control. These experiments were repeated twice.