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Items 81 to 85 of 3044 total

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  • Production of Anatoxin-a and a Novel Biosynthetic Precursor by the CyanobacteriumAphanizomenon issatschenkoi

    Selwood, A; Holland, P; Wood, S; Smith, K; McNabb, P;
    Cawthron Institute, 98 Halifax Street E, Nelson 7010, New Zealand
    Cyanobacterial blooms in New Zealand surface water resources have been surveyed and, in response to strict new standards for drinking water, more intensive monitoring for cyanotoxins has been initiated. Aphanizomenon issatschenkoi was recently identified in a New Zealand lake and was found to produce the potent neurotoxin anatoxin-a (ATX). A strain of Aph. issatschenkoi (CAWBG02) was cultured for ATX production and a novel derivative of ATX was found to account for a high proportion of the toxin content in the Aph. issatschenkoi cells. Spectroscopic data (LC-UV, liquid chromatography with ultraviolet absorption detection; LC-MS/MS, liquid chromatography with tandem mass spectrometry; LC-HRMS, liquid chromatography with high resolution mass spectrometry) identified this derivative as 11-carboxyl anatoxin-a. Although precursors with a carboxyl group on C11 have been postulated in the biosynthetic pathway for ATX from amino acids and acetate, this is the first identification of a specific intermediate. The production of ATX and the intermediate by Aph. issatschenkoi was studied under different growth conditions. Concentrations of ATX and the intermediate increased in the aerated culture to 170 μg/L and 330 μg/L, respectively, at 21 days (18 × 109 cells/L). Cell concentrations did not markedly increase during subsequent growth to 37 days. ATX concentrations decreased, and 11-carboxyl ATX concentrations continued to increase during this period. Toxin production by Aph. issatschenkoi cells was maximal at 6 days of growth (0.08−0.09 pg/cell each; 2.3 × 108 cells/L). Other ATX analogues and metabolites were not detected in the cultures. Freeze−thawing of cultures resulted in complete conversion of the intermediate to ATX with a half-life of 5 min, and this conversion was inhibited by acidification, heating of the culture to 100 °C, or addition of methanol. The implications of the findings for mechanisms of biosynthesis of anatoxins by cyanobacteria and for monitoring of water bodies for cyanotoxins are discussed.
    10.1021/es061983o
  • Mat forming toxic benthic cyanobacteria in New Zealand: species diversity and abundance, cyanotoxin production and concentrations

    Heath, MW;
    Recent research has shown that toxic cyanobacteria are more widespread in New Zealand water bodies than previously thought. However, that work has largely focused on planktonic species. Toxin production associated with benthic cyanobacteria is less widely understood despite benthic mat-forming cyanobacteria being prevalent throughout New Zealand rivers. Little is known on species responsible for toxin production, their distribution, frequency and factors triggering toxin production. This study is divided into two phases; (1) a phylogeographic study of benthic cyanobacteria from multiple rivers across New Zealand and (2) an in-depth study of spatial and temporal variability of toxic benthic cyanobacteria in two rivers. Benthic cyanobacterial mats were collected from 22 different waterbodies around New Zealand between January 2005 and December 2008 and their anatoxin content determined using liquid chromatography-mass spectrometry. Thirty seven isolates were obtained from these samples and a polyphasic approach was used to identify them. Liquid chromatography-mass spectrometry and targeted PCR were used to determine if the isolates were producing anatoxins and microcystins. Phormidium autumnale was the dominant cyanobacterium within the isolates, although molecular and morphological data indicated the existence of multiple strains within this species. Two isolates of Ph. autumnale produced anatoxin-a and formed their own clade based on partial 16S rRNA gene sequences. These data indicate that benthic Ph. autumnale mats are composed of multiple morphospecies and anatoxin production is dependant on the presence of anatoxin-producing genotypes. Microcystin production was confirmed in a potentially novel isolate, closely related to Planktothrix spp. This species was responsible for the death of a dog in the Waitaki river (South Island, New Zealand). Cyanobacterial abundance, diversity and toxin production were monitored fortnightly in an in-depth study of the Hutt and Wainuiomata rivers (Wellington, New Zealand), over a 12 month period. Environmental parameters were correlated with cyanobacterial abundance and anatoxin production at eight locations along the rivers to elucidate possible causal factors. Cyanobacterial proliferations and associated anatoxin production were spatially and temporally variable across eight different sampling sites. Both river flow and temperature had a significant effect on cyanobacterial abundance. Multiple physicochemical factors including nutrients and periphyton growth appear to be interacting to influence cyanobacterial abundance. The presence and concentration of anatoxin-a and homoanatoxin-a and their degradation products dihydro-anatoxin-a and dihydro-homoanatoxin-a were also highly variable across all sites and over time. Anatoxin concentration did not correlate with any physicochemical parameters. The results of this study have demonstrated that the prevalence of freshwater cyanotoxin-producing benthic cyanobacteria is widespread in New Zealand and that toxin concentration is variable and unpredictable. This research will assist water managers in addressing the complex management issues associated with benthic cyanobacterial proliferations. Show full item record [/handle/10063/1102?show=full]
  • Desenvolvimento de métodos analíticos por cromatografia gasosa acoplada à espectrometria de massas para a identificação e quantificação de anatoxina-A em amostras de água e florações algais

    Salazar, VCR;
    Abstract in Portuguese A poluição dos corpos d água é de grande preocupação mundial, pois a maioria da população utiliza a água doce de reservatórios, represas ou rios como principal fonte de água potável. A presença no Brasil de florações de cianobactérias capazes de produzir anatoxina-a, revela a necessidade de métodos simples e rápidos que permitam sua detecção e monitoramento. Neste trabalho foram desenvolvidos, otimizados e validados dois métodos analíticos por GC/MS para identificação e quantificação de anatoxina-a em amostras de água e florações, respectivamente. A norcocaína foi usada como padrão interno em ambos os métodos. Os íons escolhidos para serem monitorados foram (íons quantificadores sublinhados): anatoxina-a: 191,164, 293 e norcocaína: 195, 136, 168. As curvas de calibração dos métodos mostraram-se lineares nas faixas de 2.5-200 ng.mL-1 e 13-250 ng.mg-1. Os limites de detecção obtidos foram 2 ng.mL-1 e 10 ng.mg-1. Os métodos demonstraram sensibilidade e especificidade adequada para seu uso no monitoramento ambiental da anatoxina-a. Title in English Development of analytical methods by gas chromatography/mass spectrometry for anatoxin-a identification and quantification in water and algae bloom samples Keywords in English Anatoxin-a GC/MS SPE SPME
  • Desenvolvimento de métodos analíticos por cromatografia gasosa acoplada à espectrometria de massas para a identificação e quantificação de anatoxina-A em amostras de água e florações algais

    Salazar, VCR;
    Abstract in Portuguese A poluição dos corpos d água é de grande preocupação mundial, pois a maioria da população utiliza a água doce de reservatórios, represas ou rios como principal fonte de água potável. A presença no Brasil de florações de cianobactérias capazes de produzir anatoxina-a, revela a necessidade de métodos simples e rápidos que permitam sua detecção e monitoramento. Neste trabalho foram desenvolvidos, otimizados e validados dois métodos analíticos por GC/MS para identificação e quantificação de anatoxina-a em amostras de água e florações, respectivamente. A norcocaína foi usada como padrão interno em ambos os métodos. Os íons escolhidos para serem monitorados foram (íons quantificadores sublinhados): anatoxina-a: 191,164, 293 e norcocaína: 195, 136, 168. As curvas de calibração dos métodos mostraram-se lineares nas faixas de 2.5-200 ng.mL-1 e 13-250 ng.mg-1. Os limites de detecção obtidos foram 2 ng.mL-1 e 10 ng.mg-1. Os métodos demonstraram sensibilidade e especificidade adequada para seu uso no monitoramento ambiental da anatoxina-a. Title in English Development of analytical methods by gas chromatography/mass spectrometry for anatoxin-a identification and quantification in water and algae bloom samples Keywords in English Anatoxin-a GC/MS SPE SPME

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