An Environmentally-Induced Transition from the Flagellated to the Non-flagellated State in Salmonella typhimurium: the Fate of Parental Flagella at Cell Division

Abstract

SUMMARY: Bacteria in cultures of Salmonella typhimurium LT2 were peritrichously flagellated when grown in nutrient broth at 370; but most were non-flagellated when grown for 6 mean-generation times or more at 440. When a culture growing exponentially at 370 was transferred to 440, growth continued at about the same rate; but the synthesis of new flagella was largely curtailed. The fate of the parental flagella was studied by staining and counting flagella on bacteria from samples taken during growth at 440 of cultures first grown at 370. After 3 mean-generation-times the average number of flagella/flagellated bacterium had fallen from about 8 to about 2 and the proportion of flagellated bacteria from about 100 % to about 60 %. The distribution of numbers of flagella/bacterium was at all times unimodal, with the mode decreasing from about 8 to 0. In non-growing cultures at 440 there was little or no change in the average number of flagella/bacterium, in the proportion of flagellated bacteria, or in the distribution of numbers of flagella/bacterium. It is inferred that parental flagella are neither rapidly shed at 440 nor retained entirely by one daughter cell at each division but are distributed about equally between the two daughter cells.