Genetic organization of the region upstream from the Campylobacter jejuni flagellar gene flhA.

Campylobacter jejuni (Cj) is a Gram-bacterium that causes a diarrheal disease in humans. A Cj homolog of the LcrD/FlhA family of proteins was recently described [Miller et al., Infect. Immun. 61 (1993) 2930-2936]. This family includes proteins that are involved in flagellar biogenesis, such as the Cj FlhA protein, but also includes proteins found in invasive pathogens, such as the Yersinia pestis LcrD protein, that play a role in the regulation and/or secretion of virulence-related proteins. Hybridization studies indicated that both the flhA gene and upstream DNA are present in several bacterial species closely related to Cj, including C. fetus, C. lari, C. upsaliensis and C. hyointestinalis. The presence of a second flhA/lcrD homolog was not detected in Cj, indicating that a a separate homolog involved in secretion of virulence proteins may not be present. The 4-kb region immediately upstream from Cj flhA was analyzed. Three open reading frames (ORFs) were found: a 408-nucleotide (nt) gene encoding a homolog of proteins present in Escherichia coli and Desulfovibrio vulgaris, but of unknown function, a 266-nt rpsO gene and a 2823-nt gene encoding a homolog of the Bacillus subtilis SpoIIIE protein. The Cj SpoIIIE homolog had 53% similar or identical amino acids when compared to the B. subtilis protein, and like the B. subtilis protein contained a nt-binding domain and potential transmembrane (TM) regions. All three ORFs were expressed in E. coli minicells, apparently from their own promoters.(ABSTRACT TRUNCATED AT 250 WORDS)