Upon overexpression acts as a novel anti-FlhC(2)FlhD(4) factor, decreasing its DNA-binding activity, able to negatively regulate expression of flagellar class II operons including FliC. Induced by extracellular autoinducer AI-1 (Vibrio fischeri autoinducer oxoC6), in an SdiA-dependent fashion. Repressed by glucose. Induced at pH 5.0 in an RpoS-dependent fashion. Very poorly expressed in both rich and nutrient-poor medium due to inefficient translation (at protein level). A double sdiA/ydiV deletion mutant leads to decreased cAMP levels which inhibits quorum sensing system 2. Repressed by glucose. Unlike the case in Salmonella typhimurium, disruption has no effect on motility or FliC levels. Belongs to the YdiV family.