IDENTIFICATION OF GENES ENCODING COMPONENTS OF THE SWARMER CELL FLAGELLAR MOTOR AND PROPELLER AND A SIGMA-FACTOR CONTROLLING DIFFERENTIATION OF VIBRIO-PARAHAEMOLYTICUS

Vibrio parahaemolyticus possesses two distinct motility systems, the p olar system used for swimming in liquid environments and the lateral s ystem used for swarming over surfaces. Growth on surfaces induces swar mer cell differentiation and expression of the lateral motility system . Mutants, created by transposon mutagenesis of a clone expressing lat eral flagellin and gene disruption in V. parahaemolyticus, were unable to swarm and failed to make lateral flagellin; therefore, unlike the case for the polar system, there is one gene (lafA) encoding lateral f lagellin. In addition to lafA, other genes required for swarming but n ot for swimming were identified by gene replacement mutagenesis. The n ucleotide sequence of the clone determined open reading frames (ORFs) and deduced amino acid sequences showed similarities to flagellar comp onents of other bacteria: flagellin, hook-associated protein (HAP2), m otor components, and flagellar sigma factor (sigma28). Many sigma28 fa ctors have been shown to recognize cognate promoters; however, express ion of lafA in Escherichia coli required LafS, and E. coli sigma28 did not substitute. Also, there were no sequences preceding genes encodin g flagellin or HAP2 resembling the sigma28 consensus promoter. The pro duct of the sigma-like gene seems to be a unique member of the sigma28 cluster. It appears the result of requiring expression for immunodete ction of flagellin clones was that the sigma locus was fortuitously cl oned, since the sigma and lafA loci were not contiguous in the chromos ome. This work initiates identification and placement of genes in a sc heme of control for swarmer cell differentiation; three levels have be en identified in the transcriptional hierarchy.