Import systems that transport the transition metal ion across cell membranes in order to provide it for synthesis of coenzyme B12 and for incorporation into cobalt-containing enzymes.
Cobalt is a trace nutrient for prokaryotes and utilized for biosynthesis of the cobalt-containing coenzyme B12 (see also Vitamin B12), and for incorporation into noncorrin Co-containing enzymes. Animals must take up vitamin B12 with their diet or from intestinal prokaryotic producers. In higher plants, physiological roles for corrin and noncorrin cobalt enzymes have so far not been established. Nevertheless, beneficial effects of Co2+ for plant growth are known (Pilon-Smits et al. 2009). These effects may be due to stimulating growth of bacteria in the rhizosphere and of root-nodulating bacterial endosymbionts.