A promising bacterial strain for biodegradingmicrocystin-LR(MC-LR)as the sole carbon and nitrogensource was successfully isolated from Lake Dianchi,China.The strain was identified as Sphingopyxis sp.USTB-05,which was ...A promising bacterial strain for biodegradingmicrocystin-LR(MC-LR)as the sole carbon and nitrogensource was successfully isolated from Lake Dianchi,China.The strain was identified as Sphingopyxis sp.USTB-05,which was the first isolated MCs-biodegradingSphingopyxis sp.in China.The average biodegradationrate of MC-LR by Sphingopyxis sp.USTB-05 was 28.8mg·L^(-1)per day,which was apparently higher than those ofother bacteria reported so far.The optimal temperature andpH for both strain USTB-05 growth and MC-LRbiodegradation were 30℃and 7.0,respectively.Therelease of MC-LR from the cyanobacterial cells collectedfrom Lake Guishui and the biodegradation of MC-LR byboth strain and cell-free extract(CE)were investigated.The results indicated that MC-LR with the initialconcentration of 4.0 mg·L^(-1)in water was biodegraded bySphingopyxis sp.USTB-05 within 4 d,while MC-LR withthe initial concentration of 28.8 mg·L^(-1)could be completelyremoved in 3 h by CE of Sphingopyxis sp.USTB-05 containing 350 mg·L^(-1)protein.During enzymaticbiodegradation of MC-LR,two intermediate metabolitesand a dead-end product were observed on an HPLCchromatogram.Moreover,the similar scanning profiles ofMC-LR and its metabolic products indicate that the Addaside-chain of MC-LR was kept intact in all products.展开更多
Microcystin-LR (MC-LR) is the most abundant and toxic microcystin congener and has been classified as a potential human carcinogen (Group 2B) by the International Agency for Research on Cancer. However, the mechan...Microcystin-LR (MC-LR) is the most abundant and toxic microcystin congener and has been classified as a potential human carcinogen (Group 2B) by the International Agency for Research on Cancer. However, the mechanisms underlying the genotoxic effects of MC-LR during chronic exposure are still poorly understood. In the present study, human-hamster hybrid (AL) cells were exposed to MC-LR for varying lengths of time to investigate the role of nitrogen radicals in MC-LR-induced genotoxicity. The mutagenic potential at the CD59 locus was more than 2-fold higher (p 〈 0.01) in AL ceUs exposed to a cytotoxic concentration (1 μmol/L) of MC-LR for 30 days than in untreated control ceils, which was consistent with the formation of micronucleus. MC-LR caused a dose-dependent increase in nitric oxide (NO) production in treated cells. Moreover, this was blocked by concurrent treatment with the NO synthase inhibitor NC-methyl-L-arginine (L-NMMA), which suppressed MC-LR- induced mutations as well. The survival of mitochondrial DNA-depleted (pO) AL ceils was markedly decreased by MC-LR treatment compared to that in AL cells, while the CD59 mutant fraction was unaltered. These results provided clear evidence that the genotoxicity associated with chronic MC-LR exposure in mammalian cells was mediated by NO and might be considered as a basis for the development of therapeutics that prevent carcinogenesis.展开更多
基金The first and second authors did same contribution to this paper.This work was supported by the National Natural Science Foundation of China(Grant No.203777008)State Key Joint Laboratory of Environment Simulation and Pollution Control(No.09K08ESPCT),and Educational Committee of Beijing.
文摘A promising bacterial strain for biodegradingmicrocystin-LR(MC-LR)as the sole carbon and nitrogensource was successfully isolated from Lake Dianchi,China.The strain was identified as Sphingopyxis sp.USTB-05,which was the first isolated MCs-biodegradingSphingopyxis sp.in China.The average biodegradationrate of MC-LR by Sphingopyxis sp.USTB-05 was 28.8mg·L^(-1)per day,which was apparently higher than those ofother bacteria reported so far.The optimal temperature andpH for both strain USTB-05 growth and MC-LRbiodegradation were 30℃and 7.0,respectively.Therelease of MC-LR from the cyanobacterial cells collectedfrom Lake Guishui and the biodegradation of MC-LR byboth strain and cell-free extract(CE)were investigated.The results indicated that MC-LR with the initialconcentration of 4.0 mg·L^(-1)in water was biodegraded bySphingopyxis sp.USTB-05 within 4 d,while MC-LR withthe initial concentration of 28.8 mg·L^(-1)could be completelyremoved in 3 h by CE of Sphingopyxis sp.USTB-05 containing 350 mg·L^(-1)protein.During enzymaticbiodegradation of MC-LR,two intermediate metabolitesand a dead-end product were observed on an HPLCchromatogram.Moreover,the similar scanning profiles ofMC-LR and its metabolic products indicate that the Addaside-chain of MC-LR was kept intact in all products.
基金supported by the National Basic Research Program (973) of China (No. 2014CB932002)the Chinese Academy of Sciences Strategic Priority Research Program (No. XDB14030502)the National Natural Science Foundation of China (Nos. 21177133, U1232144)
文摘Microcystin-LR (MC-LR) is the most abundant and toxic microcystin congener and has been classified as a potential human carcinogen (Group 2B) by the International Agency for Research on Cancer. However, the mechanisms underlying the genotoxic effects of MC-LR during chronic exposure are still poorly understood. In the present study, human-hamster hybrid (AL) cells were exposed to MC-LR for varying lengths of time to investigate the role of nitrogen radicals in MC-LR-induced genotoxicity. The mutagenic potential at the CD59 locus was more than 2-fold higher (p 〈 0.01) in AL ceUs exposed to a cytotoxic concentration (1 μmol/L) of MC-LR for 30 days than in untreated control ceils, which was consistent with the formation of micronucleus. MC-LR caused a dose-dependent increase in nitric oxide (NO) production in treated cells. Moreover, this was blocked by concurrent treatment with the NO synthase inhibitor NC-methyl-L-arginine (L-NMMA), which suppressed MC-LR- induced mutations as well. The survival of mitochondrial DNA-depleted (pO) AL ceils was markedly decreased by MC-LR treatment compared to that in AL cells, while the CD59 mutant fraction was unaltered. These results provided clear evidence that the genotoxicity associated with chronic MC-LR exposure in mammalian cells was mediated by NO and might be considered as a basis for the development of therapeutics that prevent carcinogenesis.