Oxygen-Dependent Production and Arrangements of the Photosynthetic Pigments in Intact Cells of Rhodobacter Sphaeroides

Abstract

The development and re-arrangement of photosynthetic membrane of Rhodobacter sphaeroides were studied by absorption spectroscopy and fast induction of bacteriochlorophyll fluorescence when the cells grown under semiaerobic conditions were inoculated to aerobic medium and, after accommodation to aerobiosis, transferred to anaerobic conditions during constant illumination. After sudden transition from semiaerobic to aerobic cultures, the photochemical yield characterized by the relative variable fluorescence F_v/F_max decreased from 0.70 gradually to 0.30, the photochemical rate constant dropped from 5·10⁴ s⁻¹ to 1·10⁴ s⁻¹ and the contribution of the peripheral antenna (LH2) to the RC-LH1 core complex became less significant. The aerobic growth is characterized by bleaching of the pigment system. The transfer to anaerobiosis resulted in photosynthetic growth with opposite tendency of the parameters and the initial values were restored after a couple of cell cycling periods of doubling time of ∼4 h. The LH2 to LH1 ratio increased by a factor of 5. It was demonstrated that the fast fluorescence induction is a sensitive and non-invasing method to monitor the physiological state of the photosynthetic apparatus upon variation of the oxygen concentration of the culture.