No unique biological role for rubidium has been identified, but Rb⁺ can serve as a physiological and biochemical analog to K⁺ and NH₄⁺. In the absence of K⁺, Rb⁺ was found to restore normal or near normal growth in Streptococcus faecalis and Lactobacillus casei (MacLeod and Snell, 1948), Rhodopseudomonas capsulata (Jasper, 1978), and Oceanomonas baumannii (Brown and Cummings, 2001). Rb⁺ has been shown to effectively substitute for K⁺ in the biosynthesis of the pigment prodigiosin in Serratia marcescens (Bruce and Duff, 1968) and in the activation of aldehyde dehydrogenase in Saccharomyces cerevsiae (Black, 1951). Rb⁺ can also replace NH₄⁺ in the activation of NADP-specific glutamate dehydrogenase in the fungus Neurospora crassa (Wootton, 1983). Activation of selenophosphate synthetase in E. coli requires Mg²⁺ plus either K⁺, NH₄⁺, or Rb⁺ (Veres et al, 1994). Rb⁺ import and export can be mediated by monovalent cation/H⁺ antiport systems in bacteria (Brey et al, 1980) and yeasts (Kinclova et al, 2001; Lapathitis and Kotyk, 1998). Rb⁺ uptake via a cation uniport in Fusarium oxysporum var. lini has been proposed (Cabello-Hurtado, 2000). Rb⁺ can also induce competence for plasmid uptake in S. cerevisiae (Ito et al, 1983).

For more information:

Search Medline for rubidium metabolism AND bacteria

Black, S. Yeast aldehyde dehydrogenase. Arch Biochem Biophys. 1951;34:86-97.

MacLeod RA, Snell EE. The effect of related ions on the potassium requirements of lactic acid bacteria. J Biol Chem. 1948;176:39-52.