The flhDC genes of E.coli constitute the master operon required for the expression of the entire flagellar regulon. H-NS protein, a global regulator, is required for biogenesis of flagella, whose defect causes non-flagellation due to a reduced transcription of flhDC. In contrast to wild type, the OW1 strain produced flagella when hns mutation was introduced. Genetic tagging and mapping analyses revealed that the mutation named hcf lies in the 41min region of E.coli genome.
The ScanProm was exploited to search for a novel gene belonging to the class III flagellar regulon from the E. coli genome database. The search template includes the previously defined 4 bp (-35) and 8 bp (-10) promoter elements, presumably recognized by the flagella-specific $σ^F$, with an additional 4 bps at 3`` of the -35 consensus. Among the highly scored candidate genes obtained from the whole genome sequence, the majority was the previously identified class III genes while some of them were unknown ones. We tested ten highly scored candidates by cloning their promoter fragments into a lacZ transcriptional fusion vector. Among them, two genes, b2737 and ppdA, were found to be dependent on the presence of fliA ($σ^F$) or flhDC in their expressions.