Isolation and characterisation of a linked cluster of genes from Agrobacterium tumefaciens encoding proteins involved in flagellar basal-body structure

We report the DNA sequence of 7205 bp of the Agrobacterium tumefaciens chromosome. This contains a putative operon encoding homologues of the flagellar rod and associated proteins FlgBCG and FliE, the L and P ring proteins (FlgHI) a possible flagellum-specific export protein Flip, and two proteins of unknown function, FIgA and FliL. Several of these genes have overlapping stop and start codons. Three non-flagellate Tn5-induced mutations map to this operon: fla-11 to the first gene, encoding the rod protein FlgB; fla-15 to flgA; and fla-12 to fliL. A site-specific mutation introduced into the final gene in this cluster, fliP, also resulted in a non-flagellate phenotype. This indicates that the operon is expressed, and that at least FlgB, FIgA, FliL and FliP are required for flagellar assembly in A. tumefaciens. The bulk of this operon is conserved in the same order in Rhizobium meliloti.