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Anatoxin-a, also known as Very ..

Taste and odor problems occur worldwide in freshwater, drinking water, and in the fish industry.

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Biosynthesis of anatoxin-a(s). Origin of the carbons

The presence in the environment of cyanobacteria producing toxins represents a risk for human and animal health (). It is thus important to develop methodologies to detect these toxic microorganisms in water reservoirs, and so far, PCR-based amplification of genes responsible for the biosynthesis of these toxins is the best method (). We have been interested in the study of cyanobacteria producing the neurotoxins anatoxin-a and homoanatoxin-a (, , ). Our goals were first to identify the genes responsible for the biosynthesis of these toxins and to deepen our knowledge of this interesting group of bacteria. For that, we chose Oscillatoria sp. PCC 6506 (, , ), a filamentous benthic cyanobacterium, as our model microorganism and initiated the sequencing of its genome.

Toxins are also a risk to recreational water use and have caused number of animal poisonings.

The RFLP method was developed for simultaneous detection (amplification with anaC-gen primers []) and identification of different anatoxin producer genera present. Identification is based on the RFLP patterns produced after amplicons are digested with HhaI or HinfI. When the cyanobacterial strains were subjected to RFLP analysis, the fragmentation patterns observed were similar to those predicted by in silico analysis of the anaC sequences (; ). In addition, strains Anabaena sp. 130, Oscillatoria sp. PCC 6412, and Oscillatoria sp. PCC 9107, the anaC gene of which was not sequenced prior to RFLP analysis, produced fragmentation patterns identical to those of groups Ana, OscI, and OscII, respectively (). Due to the failure of amplification with anaC-gen primers, the method was not applied to Oscillatoria sp. PCC 10608. In accordance with the sequencing results, the Oscillatoria strains produced differing fragmentation patterns when digested with HhaI (groups OscI and OscII []). Oscillatoria strain PCC 10111 was digested with HinfI similarly to other Oscillatoria strains, but not at all with HhaI. Sequencing of the anaC-gen amplicon (GenBank accession number ) of this strain revealed a silent nucleotide substitution that abolished the only HhaI recognition site (GGC → GGC). All the characteristic fragments could also be recognized when the anaC-gen amplicons of several strains were mixed before digestion (see Fig. S1 in the supplemental material), suggesting that the RFLP method could be used to study environmental samples, where the population of potential anatoxin producers could be composed of a mixture of strains.

Anatoxin-a synthetase gene cluster of the …

PCR and qPCR detection methods were developed for anatoxin-a producing cyanobacteria.

The biosynthetic origin of the C-12 methyl group in homoanatoxin-a (1) was identified by the feeding experiment of L-[methyl-13C]-methionine in the culture of the cyanobacterium Raphidiopsis mediterranea Skuja strain LBRI 48. Remarkably high incorporation (80%) of 13C was observed at C-12. The in vivo enzymatic transformation of 1 was also examined by the prolonged culture of strain LBRI 48. The cells harvested at the stationary phase (15 days of incubation) gave higher contents of 4S-hydroxyhomoanatoxin-a (2), 4R-hydroxyhomoanatoxin-a (3), 2,3-epoxyhomoanatoxin-a (4), and 4-ketohomoanatoxin-a (5) than those from the cells collected at the late logarithmic growth phase (5 days). Compounds 2-5 would be transformed from 1 in the cells. The ratio of anatoxin-a and 1 was not significantly changed between two phases. Compound 5 was generated from 1 by air oxidation during storage even under dry and cool (-30 °C) conditions, but the oxidation was prevented in a water solution at both room temperature and -30 °C (frozen stock). Homoanatoxin-a (1) gave 2,3-dihydro-3-methoxyhomoanatoxin-a (6) during the separation procedures probably by the Michael reaction of methanol used as solvent. It should be noted that 4 was isolated for the first time from a cyanobacterium as the natural product. Compounds 3 and 5 were new members of the anatoxins.

The implications of the findings for mechanisms of biosynthesis of anatoxins by cyanobacteria and for monitoring of water bodies for cyanotoxins are discussed.

Anatoxin-a synthetase gene cluster of the cyanobacterium Anabaena sp

37; II) to develop molecular detection methods (PCR, quantitative PCR, restriction fragment length polymorphism RFLP) for the detection of potential anatoxin-a and homoanatoxin-a producers, and apply methods to environmental samples; and III) to develop a PCR-based molecular method for the detection of the producers of geosmin and MIB in cyanobacteria.

37, the gene cluster responsible for anatoxin-a biosynthesis (ana) was identified based on the comparison to the gene cluster from cyanobacteria Oscillatoria sp.

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  • Anatoxin-a Synthetase Gene Cluster of the …

    Cyanobacterial mass occurrences pose a threat to users of water due to hepatotoxic or neurotoxic strains.

  • Anatoxin-a and homoanatoxin-a are neurotoxins synthesized ..

    Anatoxin-a and homoanatoxin-a are alkaloid neurotoxins produced by strains of several cyanobacterial genera.

  • Biosynthesis of anatoxin-a(s). (2S,4S)-4 …

    Cyanobacteria also produce strong odorous metabolites that cause musty and/or earthy odor and taste in water.

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Production of anatoxin-a and a novel biosynthetic precursor ..

T1 - Biosynthesis and transformation of homoanatoxin-a in the cyanobacterium Raphidiopsis mediterranea skuja and structures of three new homologues

Lyngbyatoxin-a is a cyanotoxin produced by certain ..

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.

of the Cyanobacterium Anabaena sp

In addition, RFLP analysis of the anaC amplicons was used to simultaneously identify three anatoxin-a producer genera Anabaena, Oscillatoria, and Aphanizomenon.

BGC0000017, anatoxin biosynthetic gene cluster from [Oscillatoria] sp

With developed PCR and RFLP methods, the presence of Anabaena and Oscillatoria as potential anatoxin-a producers in Finnish freshwaters and the Baltic Sea was observed.

cyanobacteria synthesis | Biosynthesis | Natural Products

Thus, the developed method could be used for the detection of potential anatoxin-a and homoanatoxin-a producers in cyanobacterial strains and to predict the amount of anatoxin-a producers from lake water samples.

Anatoxin-a and homoanatoxin-a are neurotoxins ..

N2 - The biosynthetic origin of the C-12 methyl group in homoanatoxin-a (1) was identified by the feeding experiment of L-[methyl-13C]-methionine in the culture of the cyanobacterium Raphidiopsis mediterranea Skuja strain LBRI 48. Remarkably high incorporation (80%) of 13C was observed at C-12. The in vivo enzymatic transformation of 1 was also examined by the prolonged culture of strain LBRI 48. The cells harvested at the stationary phase (15 days of incubation) gave higher contents of 4S-hydroxyhomoanatoxin-a (2), 4R-hydroxyhomoanatoxin-a (3), 2,3-epoxyhomoanatoxin-a (4), and 4-ketohomoanatoxin-a (5) than those from the cells collected at the late logarithmic growth phase (5 days). Compounds 2-5 would be transformed from 1 in the cells. The ratio of anatoxin-a and 1 was not significantly changed between two phases. Compound 5 was generated from 1 by air oxidation during storage even under dry and cool (-30 °C) conditions, but the oxidation was prevented in a water solution at both room temperature and -30 °C (frozen stock). Homoanatoxin-a (1) gave 2,3-dihydro-3-methoxyhomoanatoxin-a (6) during the separation procedures probably by the Michael reaction of methanol used as solvent. It should be noted that 4 was isolated for the first time from a cyanobacterium as the natural product. Compounds 3 and 5 were new members of the anatoxins.

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