Isolation and characterization of pigment mutants of the blue-green alga Aphanothece stagnina

Summary Nitrosoguanidine-induced pigment mutants with elevated phycocyanin content and diminished phycoerythrin have been isolated from the phycoerythrin rich wild type blue-green alga Aphanothece stagnina. The phycocyanin: chlorophyll ratio varied among the mutant strains which invariably showed an impairment in their N₂-dependent growth and accumulation of fixed nitrogen. Phycoerythrin was virtually eliminated from the mutant strains in contrast with the wild type. The observations are in consistence with the biosynthetic interconvertibility of chromophoric precursors of the two phycobilins and perhaps a greater efficiency of phycocyanin in the oxygenic part (PSII) of photosynthesis.