FIG 1.

Western blots of PilQ from spontaneously arising penicillin-resistant mutants of PR100. (A) Spontaneous mutations in PilQ were isolated by plating PR100 cells on GCB plates containing penicillin at concentrations just above the MIC. A representative Western blot with PilQ antibody is shown for 12 out of 615 nonpiliated colonies with increased penicillin resistance. The arrows indicate bands corresponding to the SDS-resistant multimer and the SDS-labile monomer. Three classes of mutations (class 1, pilQ2-like; class 2, normal PilQ; and class 3, PilQ deletion or truncation) were identified. The mutant classes of the 12 mutant strains are shown below the blot. (B) Thirteen different class 1 pilQ mutants were backcrossed into SZ3 and analyzed by Western blotting using a PilQ antibody. All but four mutants showed complete loss of the SDS-resistant PilQ multimer; these four—G668S, G441C, D472N, and P719T—had a small amount of multimer.