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Gloeobacter violaceus — investigation of an unusual photosynthetic apparatus. Absence of the long wavelength emission of photosystem I in 77 K fluorescence spectra
Author(s) -
Koenig Friederike,
Schmidt Martin
Publication year - 1995
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1995.tb00976.x
Subject(s) - p700 , chemistry , fluorescence , photosystem i , photochemistry , chlorophyll , photosystem ii , excited state , chlorophyll a , photosynthesis , photosynthetic reaction centre , analytical chemistry (journal) , chromatography , atomic physics , biochemistry , electron transfer , physics , optics , organic chemistry
The deeply purple cyanobacterium Gloeobacter violaceus is subject of this investigation. It does not contain thylakoids, and the photosynthetic apparatus is located in the only membrane of the cell, the plasma membrane. Upon excitation with blue light, the 77 K fluorescence emission spectra of neither intact cells (excited with 427 nm) nor of the isolated plasma membrane (excited with 430 nm), show the expected long wavelength photosystem I emission characteristic for low energy chlorophylls. Maximal fluorescence emission was observed at 688 nm. independent on the excitation wavelength, 427 (430) nm blue light, exciting mainly chlorophyll, or 550 nm green light, exciting mainly phycoerythin. The ratio of P700 to chlorophyll was 175. O 2 ‐evolution was 160 μmol mg ‐1 chlorophyll h ‐1 in saturating white light; the compensation point was reached at 6 μmol m 2 s ‐1 in cultures grown at 25 μmol m 2 s ‐1 . Dark O 2 uptake was 50 μmol mg ‐1 chlorophyll h ‐1 . During adaptation to increasing white light intensities Gloeobacter reduces the amount of phycocyanin and chlorophyll per cell and strongly increases the concentration of carotenoids relative to chlorophyll. The carotenoid concentration per cell increases with increasing light intensity. Apparently, part of the carotenoids is not located in the plasma membrane.