BACKGROUND : Post-translational glycosylation of the flagellin protein is relatively common among Gram-negative
bacteria, and has been linked to several phenotypes, including flagellar biosynthesis and motility, biofilm formation,
host immune evasion and manipulation and virulence. However to date, despite extensive physiological and
genetic characterization, it has never been reported for the peritrichously flagellate Enterobacteriaceae.
RESULTS : Using comparative genomic approaches we analyzed 2,000 representative genomes of Enterobacteriaceae,
and show that flagellin glycosylation islands are relatively common and extremely versatile among members of this
family. Differences in the G + C content of the FGIs and the rest of the genome and the presence of mobile genetic
elements provide evidence of horizontal gene transfer occurring within the FGI loci. These loci therefore encode highly
variable flagellin glycan structures, with distinct sugar backbones, heavily substituted with formyl, methyl, acetyl, lipoyl
and amino groups. Additionally, an N-lysine methylase, FliB, previously identified only in the enterobacterial pathogen
Salmonella enterica, is relatively common among several distinct taxa within the family. These flagellin methylase island
loci (FMIs), in contrast to the FGI loci, appear to be stably maintained within these diverse lineages.
CONCLUSIONS : The prevalence and versatility of flagellin modification loci, both glycosylation and methylation loci,
suggests they play important biological roles among the Enterobacteriaceae.