Two different (approximately 59-kDa) flagellin subunits, FlaA and FlaB are subject to both antigenic variation and phase variation. The expression of FlaA and FlaB is controlled by different transcription factors, namely the alternative sigma28 (FlaA) and sigma54 (FlaB) transcription factors. Post-translationally modified through O-linked glycosylation. The major modification are pseudaminic acid (Pse5Ac7Ac), a nine carbon sugar that is similar to sialic acid, and an acetamidino-substituted pseudaminic acid (PseAm). There are also minor amounts of a dihydroxyproprionyl form (Pse5Pr7Pr) and an O-acetylated form (Pse5Ac7Ac8OAc). The exact role of glycosylation is unknown. The modification appears to be important for flagellar assembly and may be required for recognition by the flagellar secretion/assembly apparatus. ...
Flagella expression is associated with the cellular cycle in L. pneumophila, the bacteria are not motile while multiplying in host cells, but become motile in the later stages of the infection process. ...
Required for efficient cellular invasion. YplA, a phospholipase is secreted by this type III flagellum secretion system. YplA is required for survival of Y. enterocolitica in the Peyer's patches and for stimulation of the acute inflammatory response of the host to the infection. Contributed to the initiation of biofilm formation. ...