Genetic diversity of Cylindrospermopsis strains (cyanobacteria) isolated from four continents.
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The genetic diversity of Cylindrospermopsis strains (cyanobacteria) was examined using mainly the 16S-23S internally transcribed spacer (ITS1) sequences. Strains were grouped in three clusters: (i) America, (ii) Europe, and (iii) Africa and Australia. These results suggested a recent spread of Cylindrospermopsis across the American and European continents from restricted warm refuge areas instead of exchanges between continents. On the other hand, they also suggested a recent colonization of Australia by African strains. (+info)
Primary irritant and delayed-contact hypersensitivity reactions to the freshwater cyanobacterium Cylindrospermopsis raciborskii and its associated toxin cylindrospermopsin.
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BACKGROUND: Freshwater cyanobacteria are common inhabitants of recreational waterbodies throughout the world; some cyanobacteria can dominate the phytoplankton and form blooms, many of which are toxic. Numerous reports in the literature describe pruritic skin rashes after recreational or occupational exposure to cyanobacteria, but there has been little research conducted on the cutaneous effects of cyanobacteria. Using the mouse ear swelling test (MEST), we sought to determine whether three toxin-producing cyanobacteria isolates and the purified cyanotoxin cylindrospermopsin produced delayed-contact hypersensitivity reactions. METHODS: Between 8 and 10 female Balb/c mice in each experiment had test material applied to depilated abdominal skin during the induction phase and 10 or 11 control mice had vehicle only applied to abdominal skin. For challenge (day 10) and rechallenge (day 17), test material was applied to a randomly-allocated test ear; vehicle was applied to the other ear as a control. Ear thickness in anaesthetised mice was measured with a micrometer gauge at 24 and 48 hours after challenge and rechallenge. Ear swelling greater than 20% in one or more test mice is considered a positive response. Histopathology examination of ear tissues was conducted by independent examiners. RESULTS: Purified cylindrospermopsin (2 of 9 test mice vs. 0 of 5 control mice; p = 0.51) and the cylindrospermopsin-producing cyanobacterium C. raciborskii (8 of 10 test mice vs. 0 of 10 control mice; p = 0.001) were both shown to produce hypersensitivity reactions. Irritant reactions were seen on abdominal skin at induction. Two other toxic cyanobacteria (Microcystis aeruginosa and Anabaena circinalis) did not generate any responses using this model. Histopathology examinations to determine positive and negative reactions in ear tissues showed excellent agreement beyond chance between both examiners (kappa = 0.83). CONCLUSION: The irritant properties and cutaneous sensitising potential of cylindrospermopsin indicate that these toxicological endpoints should be considered by public health advisors and reservoir managers when setting guidelines for recreational exposure to cyanobacteria. (+info)
Occurrence of toxin-producing cyanobacteria blooms in a Brazilian semiarid reservoir.
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We report the occurrence of cyanobacterial blooms and the presence of cyanotoxins in water samples from the Armando Ribeiro Goncalves reservoir (06 degrees 08 S and 37 degrees 07 W), located in the state of Rio Grande do Norte, in the semiarid region of northeastern Brazil. The cyanobacterial species were identified and quantified during the rainy and dry seasons in the year 2000. Cyanotoxins such as microcystins, saxitoxins and cylindrospermopsins were analyzed and quantified using HPLC and ELISA methods. The mixed toxic blooms of Cylindrospermopsis raciborskii, Microcystis spp (M. panniformis, M. protocystis, M. novacekii) and Aphanizomenon spp (Aphanizomenon gracile, A. cf. manguinii, A. cf. issastschenkoi) were persistent and represented 90-100% of the total phytoplankton species. Toxic cyanobacterial blooms from the Armando Ribeiro Goncalves reservoir were analyzed and found to have three phases in relation to the annual cycle. During the rainy season, an intense toxic bloom of Cylindrospermopsis raciborskii was recorded along with saxitoxins (3.14 microg.L(-1)). During the transition period, between the rainy and dry seasons, different species of Microscytis occurred and microcystin as high as 8.8 microg.L(-1) was recorded. In the dry season, co-dominance of Cylindrospermopsis raciborskii, Microcystis spp and Aphanizomenon spp occurred and the concentrations of saxitoxin remained very low. Our results indicate the presence of microcystins (8.8 microg.L(-1)) and saxitoxins (3.14 microg.L(-1)) into the crude water, with increasing concentrations from the second fortnight of April to late May 2000. The occurrence of toxic blooms in this reservoir points to a permanent risk of cyanotoxins in supply waters, indicating the need for the implementation of bloom control measures to improve the water quality. Exposure of the local population to cyanotoxins through their potential accumulation in fish muscle must also be considered. (+info)
Characterization of the gene cluster responsible for cylindrospermopsin biosynthesis.
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Toxic cyanobacterial blooms cause economic losses and pose significant public health threats on a global scale. Characterization of the gene cluster for the biosynthesis of the cyanobacterial toxin cylindrospermopsin (cyr) in Cylindrospermopsis raciborskii AWT205 is described, and the complete biosynthetic pathway is proposed. The cyr gene cluster spans 43 kb and is comprised of 15 open reading frames containing genes required for the biosynthesis, regulation, and export of the toxin. Biosynthesis is initiated via an amidinotransfer onto glycine followed by five polyketide extensions and subsequent reductions, and rings are formed via Michael additions in a stepwise manner. The uracil ring is formed by a novel pyrimidine biosynthesis mechanism and tailoring reactions, including sulfation and hydroxylation that complete biosynthesis. These findings enable the design of toxic strain-specific probes and allow the future study of the regulation and biological role of cylindrospermopsin. (+info)
Toxicity of cylindrospermopsin, and other apparent metabolites from Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum, to the zebrafish (Danio rerio) embryo.
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The smallest known genomes of multicellular and toxic cyanobacteria: comparison, minimal gene sets for linked traits and the evolutionary implications.
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Development of a hierarchical oligonucleotide primer extension assay for the qualitative and quantitative analysis of Cylindrospermopsis raciborskii subspecies in freshwater.
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A newly-developed molecular method, hierarchical oligonucleotide primer extension (HOPE), was used to analyze various groups within the species Cylindrospermopsis raciborskii. PCR-amplified internally transcribed spacer sequences of 16S-23S from C. raciborskii in reservoir samples of Taiwan and Kinmen were examined. One of eight sequevars in the clone libraries was closely related to strains obtained from the European continent, while the others, designated of Taiwan (TW) type, belonged to a novel group. Optimized HOPE analyses showed that C. raciborskii distributed in different reservoirs with a relative abundance of 0.5% to 76.4% in the cyanobacterial communities. They further detected the concurrence of three C. raciborskii subpopulations, in which European and TW groups were predominant. The TW sequevars accounted for greater than 87.5% of C. raciborskii in the reservoirs Taihu, Yangmin, Jinsha, and Mudan, while this decreased to 55.4-58.1%, accompanied by a proportional increase of the European group, in reservoirs Lantan and Renyi. These findings revealed the complex subspecies structure within C. raciborskii and the subspecies dynamics associated with geographic locations. (+info)