In vitro synthesis of phase-specific flagellin of Salmonella

Chromatography of Salmonella flagellin at pH 8 on DEAE-cellulose separated at least four serologically distinct kinds of flagellin, a, enx, i and 1,2, eluting in that order with increasing concentration of sodium chloride. By this chromatographic technique, the preincubated cell-free extract of Escherichia coli given saltprecipitable RNA of Salmonella was shown to synthesize flagellin characteristic of the flagellar antigen type of the cells from which the RNA was derived. Two of the in vitro synthesized flagellins specifically reacted with their corresponding antiserum.When RNA was extracted from the cells of the diphasic strain propagated from a single colony, expressing either phase 1 or phase 2, the in vitro synthesized flagellin was predominantly the same as that produced by the original colony. Translation of messenger RNA specific for phase 1 flagellin was not inhibited by the presence of messenger RNA specific for phase 2. RNA extracted from the cells of a diphasic strain without any selection directed synthesis of both phase 1 and phase 2 flagellins in the ratio expected if the culture was at equilibrium with respect to phase variation. Experimental evidence is presented to support the hypothesis that phase variation is due to the alternative synthesis of phase-specific messenger RNA.