Cloning and characterization of a Campylobacter jejuni iron-uptake operon

We report that C. jejuni modifies its outer membrane protein (OMP) repertoi re when cultivated under iron-limiting conditions such as during incubation with epithelial cells. To identify genes encoding de novo expressed OMPs, a C. jejuni cosmid library was screened with antisera raised against protei ns expressed in the presence of epithelial cells. A single clone was identi fied encoding an 80-kDa antigen. Sequence analysis of subclones identified an operon of three open reading frames (ORFs) encoding proteins that are ho mologous to the E. coli ferrichrome uptake system encoded by the fhu locus. Under low-iron conditions, C, jejuni expressed the 80-kDa OMP, indicating that its expression is regulated by the presence of iron. Southern blot ana lysis indicated that six of eleven isolates of C. jejuni harbor a fhuA homo log which, like all other DNA in this region sequenced thus far, is strikin gly GC-rich (65%) compared with the C. jejuni genome (35% G+C).