Kinetic studies of the uptake of 63Ni were undertaken with two strains of Alcaligenes eutrophus, known to require nickel ions for chemolithotrophic growth. Using carbon dioxide as sole carbon source, growth is stimulated by low concentrations of nickel with optimum concentration for growth stimulation at about 0.3 micron nickel. Higher nickel concentrations were inhibitory. Heterotrophic growth on fructose was not stimulated by nickel ions.--Upon transfer into phosphate buffer freed of heavy metal ions, autotrophically grown cells exhibited rapid uptake of 63Ni which was dependent upon the presence of hydrogen, oxygen and carbon dioxide. Within 60 min nickel was accumulated from the medium, reaching 280-fold concentration in the cells. The observed uptake exhibited a temperature optimum at about 29 degrees C and was markedly inhibited by metabolic inhibitors such as arsenite, iodoacetate, methylene-blue, sodium azide and sodium cyanide. Other heavy metal ions (Zn, Co, Mn and Cu) only slightly inhibited 63Ni-uptake. The efflux of 63Ni from the cells was stimulated by 58NiCl2 and by toluene. These data indicate that nickel ions are accumulated by an energy dependent mechanism in chemolithotrophically grown cells of these strains.

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