Three potential regulators of flagellar expression present in the genome se
quence of Campylobacter jejuni NCTC 11168, the genes rpoN,flgR, and fliA, w
hich encode the alternative sigma factor sigma (54), the sigma (54)-associa
ted transcriptional activator FlgR, and the flagellar sigma factor sigma (2
8), respectively, were investigated for their role in global regulation of
flagellar expression. The three genes were insertionally inactivated in C.
jejuni strains NCTC 11168 and NCTC 11828. Electron microscopic studies of t
he wild-type and mutant strains showed that the rpoN and flgR mutants were
nonflagellate and that the fliA mutant had truncated flagella. Immunoblotti
ng experiments with the three mutants confirmed the roles of rpoN, flgR, an
d fliA in the expression of flagellin.