THE LONS GENE REGULATES SWARMER CELL-DIFFERENTIATION OF VIBRIO-PARAHAEMOLYTICUS

Vibrio parahaemolyticus differentiates from a polarly flagellated, sho rt, rod-shaped cell known as the swimmer to the elongated, hyperflagel lated, and multinucleated swarmer cell type when it is grown on a surf ace, The swarmer is adapted to movement over and colonization of surfa ces, To understand the signal transduction mechanism by which the bact erium recognizes surfaces and reprograms gene expression, we isolated a new class of mutants defective in surface sensing, These mutants wer e constitutive for swarmer cell gene expression, inappropriately expre ssing high levels of a swarmer cell gene fusion product when grown in liquid, They showed no defect in the swimming motility system, unlike all previously isolated constitutive mutants which have defects in the alternate, polar motility system, The lesions in the majority of the newly isolated mutants were found to be in a gene, lonS, which encodes a polypeptide exhibiting 81% sequence identity to the Escherichia col i Lon protein, an ATP-dependent protease, Upstream sequences preceding the lonS coding region resemble a heat shock promoter, and the homolo g extends to sequences Banking lonS. The gene order appears to be clpX lonS hupB, like the organization of the E. coli locus, V. parahaemoly ticus lonS complemented E. coli lon mutants to restore UV resistance a nd capsular polysaccharide regulation to that of the wild type, Vibrio lonS mutants were UV sensitive, In addition, when grown in liquid and examined in a light microscope, lonS mutant cells were extremely long and thus resembled swarmer cells harvested from a surface.