FIG. 6.

Two-hybrid analysis of interactions between PBPs and the cytokinetic proteins FtsQ, FtsW, and ZipN. The occurrence of interaction between the tested proteins coproduced in E. coli DHM1 cells of the BACTH system was ascertained by the production of the β-galactosidase reporter enzyme whose activity (i) turned the corresponding cells (indicated by the gray rectangles in panel A) blue on X-Gal-containing medium and (ii) reached a high value (B; beta-gal). Each bar represents the mean value of two measurements performed on the cellular extracts of three reporter clones originating from independent transformations, and the error bars represent the standard deviation. Cells producing the two interacting ZipN-fusion proteins were used as the positive control (5,900 ± 750 β-Gal units), while those producing a single or no reporter protein served as the negative controls (65 ± 50 U of background β-Gal activity).