A “successful allele” at Campylobacter jejuni contingency locus Cj0170 regulates motility; “successful alleles” at locus Cj0045 are strongly associated with mouse colonization

► Locus Cj0170 in Campylobacter jejuni strain KanR4 plays a direct role in mouse colonization. ► Locus Cj0170 encodes a positive regulator of motility. ► Successful alleles at locus Cj0045 are strongly associated with mouse colonization.