FIG. 6.

MID protein expression is shut down during phase variation. IgD binding of M. catarrhalis strains Perez112 (A and B) and RH4 (C and D) is shown before (clumping variants [A and C]) and after (nonclumping variants [B and D]) six passages. The genetic profiles of Perez112 before (9 G's) and after (8 G's) the six passages obtained by PFGE (E) and RAPD (F) were identical. M. catarrahlis strains were cultured in NB medium without shaking. A small fraction of the supernatant (without clumping bacteria) was transferred to a new tube six times in 4 weeks. IgD binding was analyzed by flow cytometry as described in the legend to Fig. 1. The numbers of G's in the poly(G) tracts were determined by DNA sequencing. Details on PFGE and RAPD are given in Materials and Methods. In panel F, the letters a and b indicate the primers A70-3 and ERIC1-R, respectively. The M. catarrhalis Bc5 strain was included as a control in panels E and F.