Regulation of flagellin glycosylation genes in Campylobacter jejuni: influence of NssR, the nitrosative stress response regulator.

Abstract

Campylobacter jejuni is one of the leading causes of food borne illness worldwide; the main cause of infection is the consumption of undercooked, contaminated poultry. Motility, mediated by single polar flagella, is necessary for Campylobacter virulence. The flagellin proteins are extensively glycosylated in C. jejuni with pseudaminic acid and related derivatives; glycosylation is required for flagella filament formation. The flagellin glycosylation locus in C. jejuni NCTC11168 comprises 50 genes, 50% are potentially involved in glycan biosynthesis and others are hypothetical; the regulatory mechanism(s) of flagellin glycosylation remain unclear. The response to nitric oxide stress in C. jejuni is regulated by NssR, which also regulates a small number of genes in the flagellin glycosylation locus; an nssR mutant has defective motility. This work aims to elucidate the mechanisms by which NssR regulates these genes and investigate the consequences of nssR mutation. Transcriptional organisation of the affected genes was deduced and chromatin immunoprecipitation (ChIP) used to map NssR binding to six potential locations in the region. Methods to measure bacterial motility were assessed and used to document the defective motility of the nssR mutant, which was found to be due to truncated, sometimes asymmetric, flagella. Finally, mass spectrometry was used to examine flagellin glycosylation in all strains.