title: Unique fluorescence properties of a cyanobacterium Gloeobacter violaceus PCC 7421: reasons for absence of the long-wavelength PSI Chl a fluorescence at -196 degrees C.
abstract: We investigated the reason for the absence of the long-wavelength PSI Chl a fluorescence at -196 degrees C in the cyanobacterium Gloeobacter violaceus using two methods: p-nitrothiophenol (p-NTP) treatment and time-resolved fluorescence spectra. The p-NTP treatment showed that PSII Chl a fluorescence was specifically affected in a manner similar to that for Synechocystis sp. PCC 6803 and spinach chloroplasts, although there were no components modified by the p-NTP treatment, indicating an absence of the long-wavelength PSI Chl a fluorescence. The time-resolved fluorescence spectra with a time resolution of 1.3 ps and spectral resolution of 1.0 nm gave no indication of the presence of the long-wavelength PSI fluorescence in the wavelength region between 700 nm and 760 nm, indicating that a very fast energy transfer among Chl a molecules could not account for the absence of the long-wavelength PSI fluorescence. From these data, it seems that the absence of the long-wavelength PSI fluorescence is due to a lack of the formation of a component responsible for the fluorescence at -196 degrees C, which may originate from a difference in the amino acid sequence. We discuss the significance of this phenomenon and interpret our findings in terms of the evolution of cyanobacteria.
authors.affiliation: Department of Physics, Biology and Informatics, Faculty of Science, Yamaguchi University, Yoshida, Yamaguchi, 753-8512 Japan. mamo_mi@bio.h.kyoto-u.ac.jp
authors.forename: Mamoru
authors.initials: M
authors.lastname: Mimuro
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ookubo
authors.forename: Daisuke
authors.initials: D
authors.lastname: Takahashi
authors.forename: Takahiro
authors.initials: T
authors.lastname: Sakawa
authors.forename: Seiji
authors.initials: S
authors.lastname: Akimoto
authors.forename: Iwao
authors.initials: I
authors.lastname: Yamazaki
authors.forename: Hideaki
authors.initials: H
authors.lastname: Miyashita
mesh_terms: D002734:Chlorophyll / Q000378:metabolism* / Q000528:radiation effects; D000077194:Chlorophyll A; D003080:Cold Temperature; D000458:Cyanobacteria / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D009596:Nitrophenols / Q000494:pharmacology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D013050:Spectrometry, Fluorescence / Q000379:methods; D013997:Time Factors
chemical_list: D009596:Nitrophenols; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll; C024836:4-nitrophenol; D000077194:Chlorophyll A