FIG 9 .

A model of RpoQ regulation of quorum-sensing-dependent phenotypes in V. fischeri. (A) At low cell density (no quorum signaling), LitR has little effect on basal levels of motility (high) and luminescence (low). (B) At moderate cell density, LitR signaling represses motility and induces luminescence as previously described (5); LitR also activates transcription of RpoQ. However, while this level of RpoQ remains insufficient to affect motility and luminescence, it does lead to increased chitinase activity. (C) At high cell density, LitR signaling increases enough to induce RpoQ to a higher level, leading to a strong repression of both motility and luminescence, as well as an induction of chitinase activity. Lines with arrowheads indicate positive regulation, while those with a bar at the end indicate negative regulation; the lines may represent a pathway with several steps of regulation.