ACIDIC-PHOSPHOLIPID DEFICIENCY REPRESSES THE FLAGELLAR MASTER OPERON THROUGH A NOVEL REGULATORY REGION IN ESCHERICHIA-COLI

The Escherichia coli pgsA3 mutation, which causes acidic-phospholipid deficiency, was found to repress the flagellar master operon, as asses sed by the beta-galactosidase activities of flhD-lacZ fusions. This ex plained the impairment of flagellar formation and motility by the muta tion. A series of deletion analysis indicated that a 40-bp region, at the 5' end of the flhD locus examined, was responsible for the repress ion of a downstream transcription initiation that was catabolite-repre ssion sensitive. This novel regulatory region was 200 bp upstream of t he first possible translation initiation site.