FIG 8.

Model of RpoN-dependent regulation of vps. RpoN is a highly interconnected node that can regulate a variety of processes through its interaction with specific activator partners. In response to quorum-sensing signals, LuxO interacts with RpoN to positively regulate the small regulatory RNAs qrr1-4, which block the translation of hapR mRNA at a low cell density. HapR is the quorum-sensing master regulator and negatively regulates vps expression through both direct regulation and the repression of the master biofilm regulators VpsR and VpsT. We demonstrate that NtrC acts as a negative regulator of vps, likely through its repression of vpsR and vpsT, and this regulatory input is dependent on the presence of RpoN. Additionally, it appears that NtrC has a modest negative impact on HapR levels. Solid lines represent direct interactions, and dashed lines indicate indirect interactions.