COLONIZATION OF CHICKS BY MOTILITY MUTANTS OF CAMPYLOBACTER-JEJUNI DEMONSTRATES THE IMPORTANCE OF FLAGELLIN-A EXPRESSION

Campylobacter jejuni strain 81116 contains two flagellin genes, flaA a nd flaB. Wild-type (WT) bacteria express flaA only, but flaB can be ex pressed under certain conditions. We have determined the importance of flagella for colonization of the avian caecum, which appears to be th e natural environment for these bacteria. Mutants in which flaA or fla B, or both had been inactivated, and motility variants, were investiga ted. Flagella are not a requisite for colonization, but mutants lackin g both flagellin genes colonized less efficiently than WT. Inactivatio n of the flaB gene, which had no effect on bacterial motility, enhance d chicken caecal colonization 1000-fold compared to WT. A variant (SF- 1) with flagella composed of flagellin A, but with poor motility, also colonized better than WT. Conversely, mutants with an inactivated fla A gene colonized 100- to 1000-fold less efficiently than WT, regardles s of their motility conferred by truncated or full-length flagellin B flagella. These results suggest that the presence of flagellin A, rath er than motility is essential for optimal bacterial colonization of ch icken caeca.