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Archives of Microbiology

, Volume 167, Issue 6, pp 343–349 | Cite as

Quinones in chlorosomes of green sulfur bacteria and their role in the redox-dependent fluorescence studied in chlorosome-like bacteriochlorophyll c aggregates

  • N.-U. Frigaard
  • Shinichi Takaichi
  • Masamitsu Hirota
  • Keizo Shimada
  • Katsumi Matsuura
Original paper

Abstract

The light-harvesting chlorosome antennae of anaerobic, photosynthetic green sulfur bacteria exhibit a highly redox-dependent fluorescence such that the fluorescence intensity decreases under oxidizing conditions. We found that chlorosomes from Chlorobium tepidum contain three isoprenoid quinone species (chlorobiumquinone, menaquinone-7, and an unidentified quinone that probably is a chlorobiumquinone derivative) at a total concentration of approximately 0.1 mol per mol bacteriochlorophyll c. Most of the cellular chlorobiumquinone was found in the chlorosomes and constituted about 70% of the total chlorosome quinone pool. When the quinones were added to artificial, chlorosome-like bacteriochlorophyll c aggregates in an aqueous solution, a high redox dependency of the fluorescence was observed. Chlorobiumquinones were most effective in this respect. A lesser redox dependency of the fluorescence was still observed in the absence of quinones, probably due to another unidentified redox-active component. These results suggest that quinones play a significant, but not exclusive role in controlling the fluorescence and in inhibiting energy transfer in chlorosomes under oxic conditions. Chlorosomes from Chloroflexus aurantiacus contained menaquinone in an amount similar to that of total quinone in Chlorobium tepdium chlorosomes, but did not contain chlorobiumquinones. This may explain the much lower redox-dependent fluorescence observed in Chloroflexus chlorosomes.

Key words Chlorobiumquinone Isoprenoid quinone Chlorosome Bacteriochlorophyll c Fluorescence Quenching Energy transfer 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • N.-U. Frigaard
    • 1
  • Shinichi Takaichi
    • 2
  • Masamitsu Hirota
    • 1
  • Keizo Shimada
    • 1
  • Katsumi Matsuura
    • 1
  1. 1.Department of Biology, Tokyo Metropolitan University, Hachioji, Tokyo 192-03, JapanJP
  2. 2.Biological Laboratory, Nippon Medical School, Kawasaki 211, JapanJP

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