Densification of cyanobacteria from a lake leading to production of β‐cyclocitral and related volatile organic compounds and species change

Abstract

The purpose of the present study was to demonstrate that the lysis with the blue color formation was caused by densification of the cyanobacteria, and related events of the species change in the cyanobacteria were induced by the resulting volatile organic compounds (VOCs), particularly β-cyclocitral. In order to obtain a high cell density of cyanobacteria in the laboratory, a concentration technique (graduated cylinder method) using the buoyancy of the gas vesicles was successfully used. The collected scum contained mainly Dolichospermum spp. and Microcystis, and the dispersed cyanobacteria were concentrated in the surface layer after several hours and the concentration ratio became approximately 10. The concentrated cyanobacteria were gradually lysed, while some of the cyanobacteria sank to the bottom, which finally died and disappeared. This method has the additional advantage that it is possible to visualize the entire lysis process. During the concentration process, β-cyclocitral and its oxidation products together with β-ionone were significantly detected. Because β-cyclocitral was easily oxidized to the corresponding carboxylic acid, the pH of the water in the graduated cylinder decreased to approximately 6. Under favorable conditions, lysis with the blue color from phycocyanin could be observed due to the acid stress. Overall, the results of the present study were consistent with the hypothesis that VOCs were produced when the cyanobacteria are highly dense, and that the lysis with the blue color formation occurs due to the higher density.

Analytical Technique Optimization on the Detection of β-cyclocitral in Microcystis Species

“…The stressed cyanobacteria finally converge on the species of Microcystis [22]. Moreover, this phenomenon was reproduced by the floating concentration of cyanobacteria [21]. These phenomena are expected to be some of the survival strategies using β-cyclocitral by Microcystis and β-cyclocitral, and related compounds are involved in the regulation of the occurrence of cyanobacteria [23].…”

“…However, the detection of β-cyclocitral and its oxidation product, β-cyclocitric acid, depended on the analytical method, solid phase micro-extraction (SPME) GC/MS or solvent extraction GC/MS [20]. Arii et al reproduced the lysis phenomenon with the blue color formation by concentrating the cyanobacteria using the cylinder method [21]. A plausive mechanism was reported for this series of phenomena.…”

Cyanobacterial Classification with the Toxicity Using MALDI Biotyper

“…Cyanobacteria have some beneficial capabilities such as oxygenic photosynthesis and nitrogen fixation, but their abnormal growth (cyanobacterial blooms) in eutrophic lakes, ponds, and reservoirs causes various environmental problems, e.g., production of moldy odors and toxic compounds. − Among the global occurrence of toxic cyanobacteria, Microcystis and its hepatotoxic cyclic heptapeptides microcystins (MCs) have been the most often reported . MCs inhibit protein serine/threonine phosphatases 1 and 2A and can cause severe liver failure. − The toxicity of MCs varies as the most common MC-LR is highly toxic but MC-RR is less. , …”