Acts as an anti-FlhC(2)FlhD(4) factor by binding to FlhD, decreasing its ability to bind DNA, and thus negatively regulates expression of flagellar class II operons, decreasing motility in nutrient-poor medium. Required for resistance to host phagocyte oxidase (By similarity). Interacts with FlhD in the FlhC(2)FlhD(4) heterohexamer, inhibiting its ability to activate transcription. Belongs to the YdiV family.