Probably a connector protein for RcsB/C regulation of biofilm and acid-resistance, providing additional signal input into the two-component signaling pathway. May serve to stimulate biofilm maturation, via the Rcs phosphorelay. Regulates expression of genes involved in acid-resistance and biofilm formation, including the RcsB/C two-component system. May be a non-specific DNA-binding protein that binds genes and/or intergenic regions via a geometric recognition. Also confers resistance to H(2)O(2). Overexpression at 28 and 16 degrees Celsius increases the production of colanic acid, an exopolysaccharide and matrix component, and reduces adhesive curli fimbriae expression. Both of these effects require RcsB; AriR probably acts upstream of the RcsB/C system to stimulate the activity and not transcription of RcsB/C. 5-fluorouracil reduction in biofilm formation requires this protein. Homodimer. Induced by low temperature (23 degrees Celsius). Repressed by the autoinducer-2 (AI-2) and by indole. Induced by 5-fluorouracil. Strongly induced at 16 degrees Celsius. Expression has been shown to be independent of RpoS (PubMed:18174134) and dependent on RpoS (PubMed:19240136), repressed by YcgE. At 16 degrees Celsius with blue light irradiation expression of this operon is absolutely dependent on YcgF for relief of YcgE repression. Part of the ycgZ-ymgA-ariR-ymgC operon, it probably also has its own promoter. Deletion increases biofilm formation. Belongs to the AriR family.