Blue Color Formation of Cyanobacteria with β-Cyclocitral

Abstract

Volatile compounds, such as beta-cyclocitral, geosmin, and 2-methylisoborneol, from cyanobacteria showed a lytic activity against cyanobacteria. Particularly, beta-cyclocitral caused an interesting color change in the culture broth from green to blue during the lysis process. In the present study, the lytic behavior of various cyanobacteria with beta-cyclocitral was investigated, and a mechanism for the blue color formation was developed. beta-Cyclocitral lysed both the laboratory strains of any genera and bloom samples including many species of cyanobacteria, and caused the characteristic color change from green to blue. beta-Cyclocitral provided a characteristic behavior, such that the absorption maxima of chlorophyll-a and beta-carotene disappeared, but that of phycocyanin still remained after 12 h, which indicated that beta-cyclocitral decomposed chlorophyll-a and beta-carotene rapidly, so that the inherent colors from the tolerant water-soluble pigments became observable in the cultured broth. This phenomenon was confirmed by another experiment using Phormidium (NIES-611), which showed a pink color derived from phycoerythrin. beta-Cyclocitral was more easily oxidized when compared with similar aldehyde compounds, so that the pH of the solution quickly decreased to 4.5. An oxidation product of beta-cyclocitral in water solution was isolated and identified as 2,6,6-trimethylcyclohexene-1-carboxylic acid. This study provides support that beta-cyclocitral derived from cyanobacteria plays an important role in the lysis of cyanobacteria and participates in the blue color formation under natural conditions.

Cyanobacterial Blue Color Formation during Lysis under Natural Conditions

“…The concentrations measured at the lysing point were lower than those from the laboratory experiments performed by Ozaki et al (14) and Harada et al (15). However, ␤-cyclocitral, whose pH-dependent distribution coefficient (log D) is 3.3, is hydrophobic; consequently, only 1/2,000 of the added ␤-cyclocitral dissolves in water and shows lytic activity (23).…”

“…Some of these volatile compounds from the cyanobacteria showed lytic activity against the cyanobacteria (14). In particular, ␤-cyclocitral caused an interesting color change in the culture broth from green to blue during the lysis process (14,15). When ␤-cyclocitral was added to the laboratory strains of any genera and to bloom samples, including many species of cyanobacteria, it caused the characteristic result, so that the absorption maxima of chlorophyll a and ␤-carotene disappeared but that of phycocyanin remained for 12 h. This indicated that the oxidation of ␤-cyclocitral leads to acidification, which then preferentially decomposes chlorophyll a and ␤-carotene rather than phycocyanin, so that the inherent color from the tolerant watersoluble pigments became observable.…”

“…These volatile compounds have been shown to possess lytic activity against cyanobacteria (14). Among these compounds, only ␤-cyclocitral caused the characteristic color change in the culture broth from green to blue during the lysis process (14,15). ␤-Cyclocitral was more easily oxidized than similar aldehyde compounds; therefore, the pH of the solution quickly decreased.…”

“…The inherent blue color from the tolerant water-soluble pigments thus become visible in the cultured broth. An oxidation product of ␤-cyclocitral in an aqueous solution was isolated and identified as 2,2,6-trimethylcyclohexene-1-carboxylic acid (␤-cyclocitric acid) (15).…”

Microcystis aeruginosa/Pseudomonas pseudoalcaligenes interaction effects on off-flavors in algae/bacteria co-culture system under different temperatures

“…These phenomena might account for that the death and decay of cyanobacteria blooms is often associated with high concentrations of VOSCs. β-Cyclocitral is considered to be the main off-flavor from cyanobacteria (Harada et al, 2009;Li et al, 2007;Yang et al, 2008), which is released during the growth of Microcystis and the disruption of cell integrity (Zhang et al, 2010b). It looks likely that the production of β-cyclocitral is related to metabolism of M. aeruginosa and bacterium (P. pseudoalcaligenes in our study) is not the origin of β-cyclocitral.…”