Aquatic environment

Microbial biodegradation of microcystin-RR by bacteriumSphingopyxis sp. USTB-05

Mulan Zhang , Gang Pan , Hai Yan


Received April 17, 2009,Revised August 28, 2009, Accepted , Available online

Volume 22,2010,Pages 168-175

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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 di erent from those reported for other strains, implying that MC-RR may undergo di erent transformations and di erent products were formed due to various bacteria in natural lakes and reservoirs.

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