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Cyanobacteria blooms produce teratogenic retinoic acids
- Wu, Xiaoqin, Jiang, Jieqiong, Wan, Yi, Giesy, John P., Hu, Jianying
- Proceedings of the National Academy of Sciences of the United States of America 2012 v.109 no.24 pp. 9477-9482
- Algae, Anabaena, Aphanizomenon, Microcystis aeruginosa, Microcystis flos-aquae, algal blooms, amphibians, aquatic ecosystems, chronic exposure, developmental stages, eutrophication, freshwater, habitats, hormones, lakes, retinoic acid, risk, teratogenicity, teratogens, wildlife, China
- Deformed amphibians have been observed in eutrophic habitats, and some clues point to the retinoic acids (RAs) or RA mimics. However, RAs are generally thought of as vertebrate-specific hormones, and there was no evidence that RAs exist in cyanobacteria or algae blooms. By analyzing RAs and their analogs 4-oxo-RAs in natural cyanobacteria blooms and cultures of cyanobacteria and algae, we showed that cyanobacteria blooms could produce RAs, which were powerful animal teratogens. Intracellular RAs and 4-oxo-RAs with concentrations between 0.4 and 4.2 × 10 ² ng/L were detected in all bloom materials, and extracellular concentrations measured in water from Taihu Lake, China, were as great as 2.0 × 10 ng/L, which might pose a risk to wildlife through chronic exposure. Further examination of 39 cyanobacteria and algae species revealed that 32 species could produce RAs and 4-oxo-RAs (1.6–1.4 × 10 ³ ng/g dry weight), and the dominant cyanobacteria species in Taihu Lake, Microcystis flos-aquae and Microcystis aeruginosa , produced high amounts of RAs and 4-oxo-RAs with concentrations of 1.4 × 10 ³ and 3.7 × 10 ² ng/g dry weight, respectively. Most genera of cyanobacteria that could produce RAs and 4-oxo-RAs, such as Microcystis , Anabaena , and Aphanizomenon , often occur dominantly in blooms. Production of RAs and 4-oxo-RAs by cyanobacteria was associated with species, origin location, and growth stage. These results represent a conclusive demonstration of endogenous production of RAs in freshwater cyanobacteria blooms. The observation of teratogenic RAs in cyanobacteria is evolutionarily and ecologically significant because RAs are vertebrate-specific hormones, and cyanobacteria form extensive and highly visible blooms in many aquatic ecosystems.