Chemotaxis of Salmonella typhimurium to Amino Acids and Some Sugars

Abstract

Patterns of chemotaxis by Salmonella typhimurium strain LT-2 to l -amino acids and to several sugars were quantitated by the Adler capillary procedure. Competition experiments indicated that LT-2 possesses three predominant receptors, or interacting sets of receptors, for amino acids. These were termed the aspartate, serine, and alanine classes, respectively. Studies with strains carrying point and deletion mutations affecting components of the phosphoenolpyruvate: glycose phosphotransferase system (PTS) made unlikely a role in primary reception of d -glucose by the three soluble PTS components, namely HPr, enzyme I, and factor III. A ptsG mutant defective in membrane-bound enzyme IIB′ of the high-affinity glucose transport system was shown to exhibit normal chemotaxis providing pleiotropic effects of the mutation were eliminated by its genotypic combination with other pts mutations or, phenotypically, by addition of cyclic AMP and substrate. A correlation was demonstrated between chemotaxis to glucose and activity of the low-affinity glucose transport complex, membrane-bound enzymes IIB:IIA, and an enzyme IIB:IIA mutant was shown to have a preponderant defect in chemotaxis to glucose and mannose. Of four systems capable of galactose transport, only the β-methylgalactoside transport system was implicated in chemotaxis to galactose. Some properties of a mutant possibly defective in processing of signals for chemotaxis to sugars is described.