FLAGELLAR FLHA, FLHB AND FLHE GENES, ORGANIZED IN AN OPERON, CLUSTER UPSTREAM FROM THE INV LOCUS IN YERSINIA-ENTEROCOLITICA

The inv gene of Yersinia enterocolitica codes for invasin, a member of the invasin/intimin-like protein family, which mediates the internali zation of the bacterium into cultured epithelial cells, The putative i nclusion of inv into a pathogenicity island was tested by investigatin g its flanking sequences. Indeed, the enteropathogenic Escherichia coi l (EPEC) intimin, a member of the same family of proteins, is encoded by eaeA, a gene which belongs to a pathogenicity island. An ORF locate d upstream from inv was of particular interest since it appeared homol ogous both to the flagellar flhA gene and to sepA, an EPEC gene lying inside the same pathogenicity island as eaeA, A mutant in this ORF was non-motile and non-flagellated while its invasion phenotype remained unaffected. These data indicated that the ORF corresponded to the flhA gene of Y, enterocolitica, Subsequently, the flhB and flhE genes, loc ated respectively upstream and downstream from flhA, were identified, The three flh genes appear to be transcribed from a single operon call ed flhB, according to the nomenclature used for Salmonella typhimurium . Intergenic sequence between flhE and inv includes a grey hole, with no recognizable function, Downstream from inv, we have detected the fl agellar flgM operon as already reported, Finally, the incongruous loca lization of inv amidst the flagellar cluster is discussed; while trans position could explain this phenomenon, no trace of such an event was detected.