Reexamination of the Carotenoid Pigments of the Unicellular Blue-green Alga Agmenellum quadruplicatum

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Abstract
A previous claim for the occurrence of antheraxanthin and the absence of typical cyanophycean xanthophylls in Agmenellum quadruplicatum has been disproven. This phycocyanin-producing prokaryote showed chlorophyll a, β-carotene, zeaxanthin, one myxoxanthophyll-like, and one myxol-like carotenoid as the major pigments. Traces of keto and other carotenoids were observed, one of which appears to be phoenicopterone or a cis-echinenone. No antheraxanthin and chlorophyll b or c were detected under all culture conditions tested. Algal chlorosis from culture aging was caused by the consecutive loss of phycocyanin and chlorophyll, but the carotenoid composition was much less affected and there was no gain of secondary or keto carotenoids. We concluded that this alga is a typical member of the Cyanophyceae in terms of pigment chemotaxonomy.