Kdp-like system in Salmonella typhimurium LT-2.

Salmonella typhimurium LT-2, as Escherichia coli K12, was able to grow in a potassium concentration-dependent manner, down to a very low concentration (< 5 microM). Its metabolic swelling also was [K+]-dependent. When the cells were subjected to hyperosmotic shock, this ion was uptaken rapidly, probably due to a K(+)-high affinity transport-system, similar to the E. coli Kdp system. The shrinkage in presence of 0.6 M NaCl, however, was more noticeable in S. typhimurium, which expressed a smaller level of intracellular K+ than E. coli. The genetic locus responsible for the ability of S. typhimurium to grow in low [K+], was mapped in nitrosoguanidine mutants and localized around min 18, close to the gal operon. This asseveration was confirmed by experiments of reversion, conjugation, and transduction. The mutants required considerably more [K+] to grow and to swell than the parental strain; in addition, below 1 mM [K+], they showed less internal [K+].