A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 ...A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 was completely degraded by USTB-05 within 36 h,which was a relatively high biodegradation rate of MC-RR.With the cell-free extract(CE)of Sphingopyxis sp.USTB-05,MC-RR was biodegraded at a more rapid biodegradation rate compared with its strain,so that initial MC-RR of 42.3 mg·L -1 was completely biodegraded within 10 h.During the bio-reaction of MC-RR catalyzed by CE,two intermediate metabolites and a dead-end product of MC-RR were observed on HPLC profiles and all of them had similar scanning profiles in the wavelength from 200 to 300 nm,indicating that the group of Adda in all products of MC-RR remained intact.展开更多
Harmful cyanobacterial blooms are a growing environmental problem worldwide in natural waters, the biodegradation is found to be the most efficient method for removing microcystins 0VICs） produced by harmful cyanobac...Harmful cyanobacterial blooms are a growing environmental problem worldwide in natural waters, the biodegradation is found to be the most efficient method for removing microcystins 0VICs） produced by harmful cyanobacteria. Based on the isolation of a promising bacterial strain of Sphingopyxis sp. USTB-05 for biodegrading MCs, we for the first time cloned and expressed a gene USTB-O5-A （HM245411） that is responsible for the first step in the biodegradation of microcystin LR （MC-LR） in E. coli DH5ct, with a cloning vector of pGEM-T easy and an expression vector of pGEX-4T-1, respectively. The cell-free extracts （CE） of recombinant E. coli DH5ct containing USTB-O5-A had high activity for biodegrading MC-LR. The initial MC-LR concentration of 40 mg/L was completely biodegraded within 1 hr in the presence of CE with a protein concentration of 0.35 mg/mL. Based on an analysis of the liquid chromatogram-mass spectrum （LC-MS）, the enzyme encoded by gene USTB-O5-A was found to be active in cleaving the target peptide bond between 3-amino-9-methoxy-2,6, 8-trimethyl-10-phenyl-deca-4,6-dienoic acid （Adda） and arginine of MC-LR, and converting cyclic MC-LR to linear MC-LR as a first product that is much less toxic than parent MC-LR, which offered direct evidence for the first step on the pathway of MC-LR biodegradation by Sphingopyxis sp. USTB-05.展开更多
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 ...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.展开更多
基金Supported by the State Key Development Program for Basic Research of China（2008CB418105） the National Natural Science Foundation of China（203777008 20621703）+1 种基金 the State Key Joint Laboratory of Environment Simulation and Pollution Control（09K08ESPCT） the Educational Committee of Beijing
文摘A promising bacterial strain for the biodegradation of Microcystins(MCs)was isolated from Dianchi lake in China and identified as Sphingopyxis sp.USTB-05 by the analysis of 16s rDNA.Initial MC-RR of 42.3 mg·L -1 was completely degraded by USTB-05 within 36 h,which was a relatively high biodegradation rate of MC-RR.With the cell-free extract(CE)of Sphingopyxis sp.USTB-05,MC-RR was biodegraded at a more rapid biodegradation rate compared with its strain,so that initial MC-RR of 42.3 mg·L -1 was completely biodegraded within 10 h.During the bio-reaction of MC-RR catalyzed by CE,two intermediate metabolites and a dead-end product of MC-RR were observed on HPLC profiles and all of them had similar scanning profiles in the wavelength from 200 to 300 nm,indicating that the group of Adda in all products of MC-RR remained intact.
基金supported by the National Natural Science Foundation of China (No. 21177009)
文摘Harmful cyanobacterial blooms are a growing environmental problem worldwide in natural waters, the biodegradation is found to be the most efficient method for removing microcystins 0VICs） produced by harmful cyanobacteria. Based on the isolation of a promising bacterial strain of Sphingopyxis sp. USTB-05 for biodegrading MCs, we for the first time cloned and expressed a gene USTB-O5-A （HM245411） that is responsible for the first step in the biodegradation of microcystin LR （MC-LR） in E. coli DH5ct, with a cloning vector of pGEM-T easy and an expression vector of pGEX-4T-1, respectively. The cell-free extracts （CE） of recombinant E. coli DH5ct containing USTB-O5-A had high activity for biodegrading MC-LR. The initial MC-LR concentration of 40 mg/L was completely biodegraded within 1 hr in the presence of CE with a protein concentration of 0.35 mg/mL. Based on an analysis of the liquid chromatogram-mass spectrum （LC-MS）, the enzyme encoded by gene USTB-O5-A was found to be active in cleaving the target peptide bond between 3-amino-9-methoxy-2,6, 8-trimethyl-10-phenyl-deca-4,6-dienoic acid （Adda） and arginine of MC-LR, and converting cyclic MC-LR to linear MC-LR as a first product that is much less toxic than parent MC-LR, which offered direct evidence for the first step on the pathway of MC-LR biodegradation by Sphingopyxis sp. USTB-05.
基金supported by the Chinese National Key Project for Basic Research (No.2008CB418105)the National Natural Science Foundation of China(No.20621703,20477050)the Important-Direction-Project funded by the Chinese Academy of Sciences
文摘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.
