TY - JOUR

T1 - Quinones in chlorosomes of green sulfur bacteria and their role in the redox-dependent fluorescence studied in chlorosome-like bacteriochlorophyll c aggregates

AU - Frigaard, Niels-Ulrik

AU - Takaichi, Shinichi

AU - Hirota, Masamitsu

AU - Shimada, Keizo

AU - Matsuura, Katsumi

PY - 1997/1/1

Y1 - 1997/1/1

N2 - 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 wits 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 Chloroflexus tepdium chlorosomes, but did not contain chlorobiumquinones. This may explain the much lower redox-dependent fluorescence observed in Chloroflexus chlorosomes.

AB - 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 wits 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 Chloroflexus tepdium chlorosomes, but did not contain chlorobiumquinones. This may explain the much lower redox-dependent fluorescence observed in Chloroflexus chlorosomes.

KW - Bacteriochlorophyll c

KW - Chlorobiumquinone

KW - Chlorosome

KW - Energy transfer

KW - Fluorescence

KW - Isoprenoid quinone

KW - Quenching

U2 - 10.1007/s002030050453

DO - 10.1007/s002030050453

M3 - Journal article

AN - SCOPUS:0030978942

VL - 167

SP - 343

EP - 349

JO - Archives of Microbiology

JF - Archives of Microbiology

SN - 0302-8933

IS - 6

ER -