A novel paralogous gene family involved in phase-variable flagella-mediated motility in Campylobacter jejuni

Abstract

Flagella-mediated motility is recognized to be one of the major factors contributing to virulence in Campylobacter jejuni. Motility of this bacterium is known to be phase variable, although the mechanism of such variation remains unknown. C. jejuni genome sequencing revealed a number of genes prone to phase variation via a slipped-strand mispairing mechanism. Many of these genes are hypothetical and are clustered in the regions involved in formation of three major cell surface structures : capsular polysaccharide, lipooligosaccharide and flagella. Among the genes of unknown function, the flagellar biosynthesis and modification region contains seven hypothetical paralogous genes designated as the motility accessory factor (maf) family. Remarkably, two of these genes (maf1 and maf4) were found to be identical and both contain homopolymeric G tracts. Using insertional mutagenesis it was demonstrated that one of the genes, maf5, is involved in formation of flagella. Phase variation of the maf1 gene via slipped-strand mispairing partially restored motility of the maf5 mutant. The maf family represents a new class of bacterial genes related to flagellar biosynthesis and phase variation. Reversible expression of flagella may be advantageous for the adaptation of C. jejuni to the varied in vivo and ex vivo environments encountered during its life cycle, as well in evasion of the host immune response.

Comparative phylogenomics of the food-borne pathogen Campylobacter jejuni reveals genetic markers predictive of infection source

“…We have previously suggested a mechanism for the loss of genes in the C. jejuni flagellin glycosylation locus (including genes cj1321-cj1326) involving homologous recombination of highly similar genes in the motility accessory factor (maf ) gene family (27). This observation may provide a genetic explanation for the apparent loss of these genes in the nonlivestock clade.…”

Passage of Campylobacter jejuni through the chicken reservoir or mice promotes phase variation in contingency genes Cj0045 and Cj0170 that strongly associates with colonization and disease in a mouse model

“…Since Cj0170 does not appear to affect flagellar structure or assembly, genes involved in chemotaxis (e.g. cheY), posttranslational modification of flagella and/or flagellar rotation top our list of candidate target genes for activation by the Cj0170 Dam methyltransferase (Karlyshev et al, 2002;Yao et al, 1997). (2) Post-translational modification of flagella.…”

Reconstitution of a Functional Toll-like Receptor 5 Binding Site in Campylobacter jejuni Flagellin

“…jejuni strains 81116 (NCTC11828) (28), NCTC 11168H1 (29), and their derivatives were grown at 37°C under microaerobic conditions (5% O 2 , 10% CO 2 , and 85% N 2 ) on saponin agar medium containing 4% lysed horse blood with the appropriate antibiotics. S. enterica ssp.…”