FIG 6.
A model for how RssB might inhibit motility under high c-di-GMP conditions. The model is based on the reported inverse coordination between motility and the σS-mediated general stress response (35). In growing cells not exposed to any particular stress, levels of the general stress sigma factor σS are kept low by rapid proteolysis by ClpXP via the adaptor RssB (see the text). Motility is enabled by the activity of multiple flagellar sigmas (collectively indicated by σF) under low-stress conditions. We propose that high c-di-GMP levels are sensed as a stress signal that stabilizes σS by some active process by which RssB prevents σS degradation. The increased competition between σS and σF decreases motility by decreased transcription of the flagellar regulon.