Serological study of bacterial flagellar hooks.

Bacterial hooks were partially purified from flagella isolated from Salmonella SJ25, by treatment with heat to depolymerize flagellar filaments and with n-butanol and calcium chloride to remove membranes. Antihook serum was obtained from a rabbit inoculated with a preparation of hooks. The serum contained antibodies directed against the flagellar filament and cell membrane. These antibodies could be removed from the serum by absorption with purified flagellar filaments and cells of a nonflagellated mutant strain. It was shown by electron microscopy that anti-SJ25-hook antibody reacts with hooks from a number of strains of Salmonella which differed from SJ25 in H and O antigens, flagellar shape, and motility. Hooks possessed by various strains of Salmonella have a common antigenicity. In addition, anti-SJ25-hook cross-reacted with hooks from Escherichia coli W3110 but did not react at all which those from strains of Serratia, Proteus, Aerobacter, and Klebsiella. It is well known that bacteria stop moving upon addition of antiflagella serum to the medium. However, the addition of purified antihook was found to have little effect on motility. At physiological ionic strength and pH, flagellin (Salmonella) can polymerize into flagellar filaments only in the presence of seeds. It was shown that a crude preparation of hooks was able to initiate in vitro polymerization of flagellin.