Flagellar filament proteins (FlaBs) of the oral spirochete Treponema denticola are modified on multiple Ser/Thr residues with a structurally novel glycan (a C7‐acylated pseudaminic acid derivative). This modification affects a highly conserved region of bacterial flagellins that interacts with Toll‐like receptor 5, and this modification is essential for flagellar assembly and motility. For details see article by Kurniyati et al . on pp. 67–85 of this issue.