PT  - JOURNAL ARTICLE
AU  - Nicholas M. Thomson
AU  - Josie L. Ferreira
AU  - Teige R. Matthews-Palmer
AU  - Morgan Beeby
AU  - Mark J. Pallen
TI  - Giant flagellins form thick flagellar filaments in two species of marine γ-proteobacteria
AID  - 10.1101/221366
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 221366
4099  - http://biorxiv.org/content/early/2018/09/20/221366.short
4100  - http://biorxiv.org/content/early/2018/09/20/221366.full
AB  - Flagella, the primary means of motility in bacteria, are helical filaments that function as microscopic propellers composed of thousands of copies of the protein flagellin. Here, we show that many bacteria encode “giant” flagellins, greater than a thousand amino acids in length, and that two species that encode giant flagellins, the marine γ- proteobacteria Bermanella marisrubri and Oleibacter marinus, produce monopolar flagellar filaments considerably thicker than filaments composed of shorter flagellin monomers. We confirm that the flagellum from B. marisrubri is built from its giant flagellin. Phylogenetic analysis reveals that the mechanism of evolution of giant flagellins has followed a stepwise process involving an internal domain duplication followed by insertion of an additional novel insert. This work illustrates how “the” bacterial flagellum should not be seen as a single, idealised structure, but as a continuum of evolved machines adapted to a range of niches.