Acts as an anti-CsrA protein, binds CsrA and prevents it from repressing translation of its target genes, one of which is flagellin. Binds to flagellin and participates in the assembly of the flagellum (Probable). Antagonizes CsrA-mediated translational repression of flaA in a promoter-independent manner, leading to expression of FlaA and probably other flagellar genes. Binds to FlaA, which releases CsrA to repress translation of flaA mRNA. Also has a negative effect on flaA transcription, and influences the localization of flaA mRNA to the poles of short, probably elongating, cells. Interacts with translational regulator CsrA and flagellin A (flaA) (PubMed:27229370). No longer autoagglutinates, loss of motility and decreased ability to invade human cell line (PubMed:11895937). Significantly decreased translation of flagellin A, 2-fold increase in flaA mRNA levels. Has 1 short flagella, the average swimming distance decreases about 30%. The mRNA for flaA is no longer localized to the cell poles in short, probably elongating, cells. A double csrA-fliW deletion expresses the same amount of flagellin A as the csrA deletion, has 2 wild-type length flagella, a wild-type swimming distance and restored localization of flaA mRNA to the poles of short, probably elongating, cells. Belongs to the FliW family.