Microbial biodegradation of microcystin-RR by bacterium Sphingopyxis sp. USTB-05

摘要

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 NH 2 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.