The Influence of Temperature on the Motility of Pasteurella pseudotuberculosis

Summary: Grown at 22° Pasteurella pseudotuberculosis was motile and had flagella and H antigen; grown at 37° it was non-motile and had neither flagella nor H antigen. The change occurred over a narrow range of temperature about 30°.Cells grown at 37° when transferred to 22° developed flagella without cell division; cells grown at 22° when transferred to 37° became non-motile, due to an unexplained adverse effect indicated by a high death-rate. It appeared that different metabolic processes were used at the two temperatures; it was not necessary to postulate the selection of a naturally occurring mutant and no evidence was obtained for the existence of an extracellular enzyme which would destroy flagella at 37°. In addition to the ‘short-term’ effect there was a ‘long-term’ effect of temperature shown by a difference in degree of motility and rate of growth (at 22°)of cultures grown for several months at 22 or 37°.This may have been an extension of the ‘short-term’ effect, a period of training being required for the optimal functioning of the metabolic processes concerned. The long-term effect could be reversed by prolonged cultivation of the 22° substrain at 37° and vice versa. Preliminary experiments indicated that virulence was affected by the temperature of cultivation.