Analysis of microcystins and microcystin genes in 60–170-year-old dried herbarium specimens of cyanobacteria

• Published in: Harmful algae 2012-03, Vol.15, p.47-52
• Main Authors: Metcalf, J.S., Beattie, K.A., Purdie, E.L., Bryant, J.A., Irvine, L.M., Codd, G.A.
• Format: Article
• Language: English
• Subjects: Algae; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; biosynthesis; case studies; Cyanobacteria; desorption; ELISA; Fundamental and applied biological sciences. Psychology; genes; Herbarium; high performance liquid chromatography; HPLC; immunoassays; ionization; ions; MALDI-TOF; mass spectrometry; mica; Microcystins; natural history; PCR; phylogeny; Plant cytology, morphology, systematics, chorology and evolution; Plants and fungi; polymerase chain reaction; retrospective studies; Thallophyta
• ISSN: 1568-9883; 1878-1470
• DOI: 10.1016/j.hal.2011.11.004

► Microcystins were detected in century-old dried herbarium specimens. ► DNA associated with microcystin synthetases was detected in century-old herbarium specimens. ► Microcystins were more readily detected than microcystin synthetase DNA. ► Dried herbarium specimens may be invaluable to understand long-term changes at sites with a history of cyanobacterial blooms. Subsamples of cyanobacteria which had been stored as herbarium specimens at the Natural History Museum, London (BM), were analysed for the presence of microcystins and for genes involved in their biosynthesis using PCR. The samples had been collected worldwide between 1839 and 1950 and stored as dried specimens on paper, or between thin sheets of mica, under ambient conditions in the dark. Specimens for analysis were selected on the assumption that the chosen genera or species identified at the time of collection would have had a high potential for microcystin production based on current knowledge of the phylogeny of microcystin biosynthesis among the cyanobacteria. Of the 30 specimens analysed, 46% were positive for microcystins by high performance liquid chromatography with photodiode array detection and 83% were positive for the toxins according to microcystin immunoassay. Ninety seven percent of the specimens had ions which corresponded with known microcystins according to matrix-assisted laser desorption ionization time of flight mass spectrometry and 17% of the samples showed positive PCR bands for the mcyD gene for microcystin synthetase. These results demonstrate the potential for long-term survival of microcystins, and to a lesser extent of microcystin synthetase genes in herbarium specimens of dried cyanobacteria. They also offer the possibility for comparative studies on cyanotoxin occurrence at identifiable sites then and now, and of the use of archived cyanobacterial specimens in retrospective studies in the case of ecotoxicological investigations at the sampling locations.