海洋におけるビタミンB₁₂ をめぐる生物間相互作用（特集：農芸化学分野におけるビタミン・バイオファクター研究の最前線）

抄録

Vitamin B₁₂ compounds are synthesized by only certain bacteria, thaumarchaeota, and cyanobacteria in marine system. Cyanobacteria do not synthesize vitamin B₁₂ but rather produce pseudovitamin B₁₂ , which is inactive in some microalgae as well as humans. Thus, vitamin B₁₂ and pseudovitamin B₁₂ co-exist in the surface ocean (photic zone, depth 0–200 m). Thaumarchaeota is the major producer of vitamin B₁₂ in the deeper ocean (mesopelagic zone, depth 200–300 m). Pseudovitamin B₁₂ formed by cyanobacteria can be remodeled to vitamin B₁₂ by some microalgae. As almost half of the species of algae require vitamin B₁₂ , such biological interactions over vitamin B₁₂ play pivotal roles in algal growth. Vitamin B₁₂ synthesized by certain bacteria and thaumarchaeota is transferred via algae and then concentrated into fish and shellfish bodies in the marine food chain.