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Cylindrospermopsin and saxitoxin synthetase genes in Cylindrospermopsis raciborskii strains from Brazilian freshwater.

Hoff-Risseti C, Dörr FA, Schaker PD, Pinto E, Werner VR, Fiore MF - PLoS ONE (2013)

Bottom Line: Attempts to PCR amplify cyrJ gene fragments from the four strains were unsuccessful.Phylogenetic analysis grouped the nucleotide sequences together with their homologues found in known CYN synthetase clusters of C. raciborskii strains with high bootstrap support.This discovery suggests a shift in the type of cyanotoxin production over time of South American strains of C. raciborskii and contributes to the reconstruction of the evolutionary history and diversification of cyanobacterial toxins.

View Article: PubMed Central - PubMed

Affiliation: Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, São Paulo, Brazil ; Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, São Paulo, Brazil.

ABSTRACT
The Cylindrospermopsis raciborskii population from Brazilian freshwater is known to produce saxitoxin derivatives (STX), while cylindrospermopsin (CYN), which is commonly detected in isolates from Australia and Asia continents, has thus far not been detected in South American strains. However, during the investigation for the presence of cyrA, cyrB, cyrC and cyrJ CYN synthetase genes in the genomes of four laboratory-cultured C. raciborskii Brazilian strains, the almost complete cyrA gene sequences were obtained for all strains, while cyrB and cyrC gene fragments were observed in two strains. These nucleotide sequences were translated into amino acids, and the predicted protein functions and domains confirmed their identity as CYN synthetase genes. Attempts to PCR amplify cyrJ gene fragments from the four strains were unsuccessful. Phylogenetic analysis grouped the nucleotide sequences together with their homologues found in known CYN synthetase clusters of C. raciborskii strains with high bootstrap support. In addition, fragments of sxtA, sxtB and sxtI genes involved in STX production were also obtained. Extensive LC-MS analyses were unable to detect CYN in the cultured strains, whereas the production of STX and its analogues was confirmed in CENA302, CENA305 and T3. To our knowledge, this is the first study reporting the presence of cyr genes in South American strains of C. raciborskii and the presence of sxt and cyr genes in a single C. raciborskii strain. This discovery suggests a shift in the type of cyanotoxin production over time of South American strains of C. raciborskii and contributes to the reconstruction of the evolutionary history and diversification of cyanobacterial toxins.

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Related in: MedlinePlus

Maximum likelihood phylogenetic tree based on the 16S rRNA gene sequences showing the relationships of the studied cyanobacteria (in bold).Bootstrap test (1,000 resamplings) was performed and values >50% for ML and NJ analyses are shown over the nodes. Branch lengths are proportional to the number of substitutions per site (see scale bar). Taxon name in red or blue denotes STX or CYN producer strains, respectively.
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pone-0074238-g006: Maximum likelihood phylogenetic tree based on the 16S rRNA gene sequences showing the relationships of the studied cyanobacteria (in bold).Bootstrap test (1,000 resamplings) was performed and values >50% for ML and NJ analyses are shown over the nodes. Branch lengths are proportional to the number of substitutions per site (see scale bar). Taxon name in red or blue denotes STX or CYN producer strains, respectively.

Mentions: In the phylogenetic tree, the 16S rRNA gene sequences of the C. raciborskii strains fall within a highly supported (bootstrap values of 99 and 100% for ML and NJ algorithms, respectively) major clade containing sequences of planktonic members of C. raciborskii isolated from several countries and an internal separated clade with members of Raphidiopsis genus (Figure 6). Within this major clade, the Brazilian and Australian strains formed distinct clades according to their origin but with low supported bootstrap. Strains of North American, African, European and Asian origin were mixed in other internal clades. The evolutionary relatedness of the four cyanobacterial strains (C. raciborskii AWT205, C. raciborskii CS-505, Aphanizomenon sp. 10E6 and Oscillatoria sp. PCC 6506) with the cyr clusters already described can be visualized in the phylogenetic tree. The phylogeny of the polyphyletic genus Aphanizomenon that possess several CYN and STX producer strains was also given in the phylogenetic tree. After revision of several genera of cyanobacteria, new designation for some of them was adopted and it is also shown in the phylogenetic tree.


Cylindrospermopsin and saxitoxin synthetase genes in Cylindrospermopsis raciborskii strains from Brazilian freshwater.

Hoff-Risseti C, Dörr FA, Schaker PD, Pinto E, Werner VR, Fiore MF - PLoS ONE (2013)

Maximum likelihood phylogenetic tree based on the 16S rRNA gene sequences showing the relationships of the studied cyanobacteria (in bold).Bootstrap test (1,000 resamplings) was performed and values >50% for ML and NJ analyses are shown over the nodes. Branch lengths are proportional to the number of substitutions per site (see scale bar). Taxon name in red or blue denotes STX or CYN producer strains, respectively.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756036&req=5

pone-0074238-g006: Maximum likelihood phylogenetic tree based on the 16S rRNA gene sequences showing the relationships of the studied cyanobacteria (in bold).Bootstrap test (1,000 resamplings) was performed and values >50% for ML and NJ analyses are shown over the nodes. Branch lengths are proportional to the number of substitutions per site (see scale bar). Taxon name in red or blue denotes STX or CYN producer strains, respectively.
Mentions: In the phylogenetic tree, the 16S rRNA gene sequences of the C. raciborskii strains fall within a highly supported (bootstrap values of 99 and 100% for ML and NJ algorithms, respectively) major clade containing sequences of planktonic members of C. raciborskii isolated from several countries and an internal separated clade with members of Raphidiopsis genus (Figure 6). Within this major clade, the Brazilian and Australian strains formed distinct clades according to their origin but with low supported bootstrap. Strains of North American, African, European and Asian origin were mixed in other internal clades. The evolutionary relatedness of the four cyanobacterial strains (C. raciborskii AWT205, C. raciborskii CS-505, Aphanizomenon sp. 10E6 and Oscillatoria sp. PCC 6506) with the cyr clusters already described can be visualized in the phylogenetic tree. The phylogeny of the polyphyletic genus Aphanizomenon that possess several CYN and STX producer strains was also given in the phylogenetic tree. After revision of several genera of cyanobacteria, new designation for some of them was adopted and it is also shown in the phylogenetic tree.

Bottom Line: Attempts to PCR amplify cyrJ gene fragments from the four strains were unsuccessful.Phylogenetic analysis grouped the nucleotide sequences together with their homologues found in known CYN synthetase clusters of C. raciborskii strains with high bootstrap support.This discovery suggests a shift in the type of cyanotoxin production over time of South American strains of C. raciborskii and contributes to the reconstruction of the evolutionary history and diversification of cyanobacterial toxins.

View Article: PubMed Central - PubMed

Affiliation: Center for Nuclear Energy in Agriculture, University of São Paulo, Piracicaba, São Paulo, Brazil ; Faculty of Pharmaceutical Sciences, University of São Paulo, São Paulo, São Paulo, Brazil.

ABSTRACT
The Cylindrospermopsis raciborskii population from Brazilian freshwater is known to produce saxitoxin derivatives (STX), while cylindrospermopsin (CYN), which is commonly detected in isolates from Australia and Asia continents, has thus far not been detected in South American strains. However, during the investigation for the presence of cyrA, cyrB, cyrC and cyrJ CYN synthetase genes in the genomes of four laboratory-cultured C. raciborskii Brazilian strains, the almost complete cyrA gene sequences were obtained for all strains, while cyrB and cyrC gene fragments were observed in two strains. These nucleotide sequences were translated into amino acids, and the predicted protein functions and domains confirmed their identity as CYN synthetase genes. Attempts to PCR amplify cyrJ gene fragments from the four strains were unsuccessful. Phylogenetic analysis grouped the nucleotide sequences together with their homologues found in known CYN synthetase clusters of C. raciborskii strains with high bootstrap support. In addition, fragments of sxtA, sxtB and sxtI genes involved in STX production were also obtained. Extensive LC-MS analyses were unable to detect CYN in the cultured strains, whereas the production of STX and its analogues was confirmed in CENA302, CENA305 and T3. To our knowledge, this is the first study reporting the presence of cyr genes in South American strains of C. raciborskii and the presence of sxt and cyr genes in a single C. raciborskii strain. This discovery suggests a shift in the type of cyanotoxin production over time of South American strains of C. raciborskii and contributes to the reconstruction of the evolutionary history and diversification of cyanobacterial toxins.

Show MeSH
Related in: MedlinePlus