Biodegradation is the key factor that determines the fate of microcystin in aquatic ecosystem and its toxicological effects on aquatic organisms. This paper reviewed the studies on biodegradation of microcystin by aquatic bacteria, plants, invertebrates and fishes. Different groups of aquatic organisms showed different pathways of microcystin degradation. Aquatic bacteria Sphingomonas sp, Pseudomonas aeruginosa and Ralstonia solanacearum had the ability of biodegradation of microcystin. Degradation of microcystin-LR in Sphingomonas sp was carried out by at least three intracellular hydrolytic enzymes, one of them was termed microcystinase. While the degradation of microcystin in Pseudomonas aeruginosa was carried out by alkaline protease. The pathway of microcystin degradation in Ralstonia solanacearum was unclear. For aquatic plants, invertebrates and fishes, microcystin was mainly biotransformed into a conjugate product with GSH, which is catalyzed by glutathione S-transferases. This paper also discussed the bioremediation strategies of microcystin in aquatic environments.
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