β-N-methylamino-L-alanine(BMAA)is an environmental neurotoxin thought to be produced by cyanobacteria.However,the cyanobacterial origin of BMAA remains controversial.The detection method and culture conditions of cya...β-N-methylamino-L-alanine(BMAA)is an environmental neurotoxin thought to be produced by cyanobacteria.However,the cyanobacterial origin of BMAA remains controversial.The detection method and culture conditions of cyanobacteria are often cited as factors behind the discrepancy of published results.We showed previously that BMAA was highly toxic to the cyanobacterium Nostoc PCC 7120,and it is taken up via an amino acid transport system.Using a mutantΔnatAΔbgtA deficient in amino acid transport as a genetic control,we show here that BMAA taken up from the medium can be detected quantitatively at a threshold similar to,or below those reported,but was undetectable in the mutant.The BMAA isomer,2,4-diaminobutanoic acids(DAB),but not BMAA,could be detected in cell free extracts of Nostoc PCC 7120.Long-term(20 days)diazotrophic growth or nonlimiting supply of phosphate,conditions reported to enhance BMAA synthesis,did not lead to the detection of BMAA.An UPLC-MS/MS signal with a similar retention time to BMAA was found after prolonged diazotrophic incubation,but did not have fragment ions of BMAA after further analysis.When extended to 29 different cyanobacterial strains and 6 natural cyanobacterial bloom samples,none of them was found to produce BMAA.The cytotoxicity of BMAA to cyanobacteria,and the lack of a cellular protective mechanism against such toxicity,contradict the presence of a BMAA synthesis pathway in these organisms.More specific methods for BMAA detection in vivo need to be developed to clarify the cyanobacterial origin of BMAA.展开更多
Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The earl...Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">determine whether juvenile alewife switch</span></span><span style="font-family:Verdana;">es</span><span style="font-family:Verdana;"> to feeding</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">largely on cyanobacteria and whether cyanotoxins microcystin (MC) and</span><span style="font-family:;" "=""> <i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = <sub>-</sub></span><span style="font-family:;" "=""><span style="font-family:Verdana;">5.503 + (3.101 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log Length). Mean MC (0.003 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><su展开更多
基金supported by the Featured Institute Service Project from the Institute of Hydrobiology,the Chinese Academy of Sciences(Grant No.:Y85Z061601).
文摘β-N-methylamino-L-alanine(BMAA)is an environmental neurotoxin thought to be produced by cyanobacteria.However,the cyanobacterial origin of BMAA remains controversial.The detection method and culture conditions of cyanobacteria are often cited as factors behind the discrepancy of published results.We showed previously that BMAA was highly toxic to the cyanobacterium Nostoc PCC 7120,and it is taken up via an amino acid transport system.Using a mutantΔnatAΔbgtA deficient in amino acid transport as a genetic control,we show here that BMAA taken up from the medium can be detected quantitatively at a threshold similar to,or below those reported,but was undetectable in the mutant.The BMAA isomer,2,4-diaminobutanoic acids(DAB),but not BMAA,could be detected in cell free extracts of Nostoc PCC 7120.Long-term(20 days)diazotrophic growth or nonlimiting supply of phosphate,conditions reported to enhance BMAA synthesis,did not lead to the detection of BMAA.An UPLC-MS/MS signal with a similar retention time to BMAA was found after prolonged diazotrophic incubation,but did not have fragment ions of BMAA after further analysis.When extended to 29 different cyanobacterial strains and 6 natural cyanobacterial bloom samples,none of them was found to produce BMAA.The cytotoxicity of BMAA to cyanobacteria,and the lack of a cellular protective mechanism against such toxicity,contradict the presence of a BMAA synthesis pathway in these organisms.More specific methods for BMAA detection in vivo need to be developed to clarify the cyanobacterial origin of BMAA.
文摘Alosa pseudoharengus<span style="font-family:;" "=""><span style="font-family:Verdana;"> is an anadromous fish that migrates from marine to freshwaters to spawn. The early larval and juvenile forms are known to be planktivorous, where heavy feeding upon their preferred food source of large crustacean zooplankton often results in changes to composition and size structure within this trophic guild which in turn can result in shifts within the trophic spectrum and a classic trophic cascade. In this study of Lower Mill Pond, Brewster MA, we evaluated the feeding strategy of juvenile </span><i><span style="font-family:Verdana;">Alosa</span></i><span style="font-family:Verdana;"> to </span><span style="font-family:Verdana;">determine whether juvenile alewife switch</span></span><span style="font-family:Verdana;">es</span><span style="font-family:Verdana;"> to feeding</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">largely on cyanobacteria and whether cyanotoxins microcystin (MC) and</span><span style="font-family:;" "=""> <i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-methlyamino-L-alanine (BMAA) bioaccumulate in their muscle tissue. Within 15</span></span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">-</span><span style="font-family:;" "=""> </span><span style="font-family:Verdana;">30 days of their estimated spawning date, overexploitation of crustacean zooplankton resulted in a shift from planktivory to benthic detritivory for the majority of their life history, although this did not reduce their condition based on weight-length relationships (Log Wwt. = <sub>-</sub></span><span style="font-family:;" "=""><span style="font-family:Verdana;">5.503 + (3.101 </span><span style="font-family:Verdana;">×</span><span><span style="font-family:Verdana;"> Log Length). Mean MC (0.003 μg<span style="font-family:Verdana, Helvetica, Arial;white-space:normal;background-color:#FFFFFF;">·</span>g<span style="font-size:10px;"><su
