VIBRIO-PARAHAEMOLYTICUS FLAJ, A HOMOLOG OF FLIS, IS REQUIRED FOR PRODUCTION OF A FLAGELLIN

The flaA locus of Vibrio parahaemolyticus encodes one of the four pola r flagellin genes, the flagellum-capping protein HAP2, and three addit ional flagellar genes. Sequence analysis downstream of the gene encodi ng HAP2 revealed the region to be similar to the fliD (HAP2) locus of Pseudomonas aeruginosa. The deduced protein sequences for the newly id entified genes suggest that one protein belongs to the family of trans criptional regulatory proteins known to interact with sigma(54), one m ay be a rod component of the flagellum, and one resembles the FliS pro tein. fliS is an essential flagellar gene in many bacteria; however it s function is not clear. The V. parahaemolyticus polar flaC flagellin gene was poorly expressed in Escherichia coil. Production of FlaC was stimulated by provision of the flaA locus in trans. Dissection of this locus revealed that the fliS-like gene, flaJ, was required for increa sed expression of flaC. Stimulation by FlaJ occurred in E. coil mutant s defective in either the master flagellar-controlling operon or the g ene encoding the flagellar sigma(28). Therefore the effect of FlaJ was not mediated through flagellar proteins. Nor was it mediated through sigma(54), for enhanced FlaC production was observed in mutants with d efects in the gene encoding sigma(54).