POTASSIUM TRANSPORT MUTANT OF ESCHERICHIA COLI B. ANALYSIS OF POTASSIUM MOVEMENTS.
Rept. for Jun 64-Dec 65,
SCHOOL OF AEROSPACE MEDICINE BROOKS AFB TEX
Pagination or Media Count:
A second mutant of Escherichia coli B strain RD-2 with impaired K transport was isolated with nitroguanidine as the mutagenic agent. Except for its K requirement, RD-2 manifests the same nutritional requirements as the parent strain and contrasts with RD-1, which was shown to be deficient both in K transport and in methionine biosynthesis. RD-2 will not grow in a low K media 20 micro M. K which supports growth of the parent strain. Electron microscopic examination of the two strains reveals no differences in surface layer ultrastructure to account for the transport impairment. Potassium accumulation studies demonstrate that the mutant low K growth failure is attributable to a K accumulation impairment. In contrast to the parent strain, RD-2 cannot accumulate K from the low K media. Addition of K to a nonaccumulating low K suspension of RD-2 stimulates uptake of K, thus establishing viability of the cells. Measurement of low K steady-state tracer fluxes yields flux values for RD-2, which are one-third those of the parent strain, and the calculated influx rate constants are consistent with the interpretation that RD-2s accumulation failure is due to an influx impairment. Author