title: Microbial biodegradation of microcystin-RR by bacterium Sphingopyxis sp. USTB-05.
abstract: A strain, USTB-05, isolated from Lake Dianchi, China, degraded the cyanobacterial toxin microcystin-RR (MC-RR) at the rate of 16.7 mg/L per day. Analysis of 16S rDNA sequence showed that the strain was Sphingopyxis sp. Enzymatic degradation pathways for MC-RR by Sphingopyxis sp. USTB-05 were identified. Adda-Arg peptide bond of MC-RR was cleaved and then a hydrogen and a hydroxyl were combined onto the NH2 group of Adda and the carboxyl group of arginine to form a linear molecule as intermediate product within the first few hours. Then, through dehydration reaction, two hydrogen of amino group on arginine reacted with adjacent hydroxyl on carbon to form a linear MC-RR with two small peptide rings as the final product after 24 hr. These biodegradation pathways were different from those reported for other strains, implying that MC-RR may undergo different transformations and different products were formed due to various bacteria in natural lakes and reservoirs.
authors.affiliation: State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. zhangmulanmine@yahoo.com.cn
authors.forename: Mulan
authors.initials: M
authors.lastname: Zhang
authors.forename: Gang
authors.initials: G
authors.lastname: Pan
authors.forename: Hai
authors.initials: H
authors.lastname: Yan
mesh_terms: D001673:Biodegradation, Environmental; D005618:Fresh Water; D007700:Kinetics; D008387:Marine Toxins; D052998:Microcystins / Q000737:chemistry / Q000378:metabolism*; D015394:Molecular Structure; D010802:Phylogeny; D042301:Sphingomonadaceae / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism
chemical_list: D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; C063855:microcystin RR