Light Intensity Adaptation and Phycobilisome Composition of Microcystis aeruginosa

• Published in: Plant physiology (Bethesda) Vol. 79; no. 4; pp. 983 - 987
• Main Authors: Shirley Raps, J. Helen Kycia, Ledbetter, Myron C., Siegelman, Harold W.
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.12.1985
• Subjects: Amino acids; Bacteriology; Biological and medical sciences; Cyanobacteria; Electron micrographs; Fundamental and applied biological sciences. Psychology; Gels; Luminous intensity; Microbiology; Monomers; Morphology, structure, chemical composition; Phycobilisome; Stoichiometry; Thylakoids; Trimers; Microcystis aeruginosa; Intensity; Light; Phycobilisome; Cyanobacteria; Bacteria; Chemical composition; Photosynthesis; Photoregulation; Adaptation
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.79.4.983

Phycobilisomes isolated from Microcystis aeruginosa grown to mid-log at high light (270 microeinsteins per square meter per second) or at low light intensities (40 microeinsteins per square meter per second) were found to be identical. Electron micrographs established that they have a triangular central core apparently consisting of three allophycocyanin trimers surrounded by six rods, each composed of two hexameric phycocyanin molecules. The apparent mass of a phycobilisome obtained by gel filtration is 2.96 × 106 daltons. The molar ratio of the phycobiliproteins per phycobilisome is 12 phycocyanin hexamers:9 allophycocyanin trimers. The electron microscopic observations combined with the phycobilisome apparent mass and the phycobiliprotein stoichiometry data indicate that M. aeruginosa phycobilisomes are composed of a triangular central core of three stacks of three allophycocyanin trimers and six rods each containing two phycocyanin hexamers. Adaptation of M. aeruginosa to high light intensity results in a decrease in the number of phycobilisomes per cell with no alteration in phycobilisome composition or structure.