A New Type of Light-Harvesting Complex Detected when Growing Rhodopseudomonas palustris under Low Light Intensity Conditions.

The predominance of the maximum at 800 nm for the light-harvesting complex LH4 (B800) and at 850 nm for LH2 (B800-850) from Rps. palustris is determined by the composition of αß-polypeptides and pigments. In low light (LL) for Rps. palustris, strain KM 286 (1e5), along with LH4, the LL LH2 complex was synthesized with the same absorption at 800 and 850 nm. It differed from the LH4 and LH2 complex, which is synthesized under high illumination, in the composition and content of carotenoids (Car) and bacteriochlorophyll a (BChl a). LH4 differed from LL LH2 and LH2 by an additional emission maximum at 766 nm in the BChl a fluorescence spectra. All three complexes had approximately the same level (about 45%) of the energy transfer efficiency from Car to BChl a. Isolation of LL LH2 complex from Rps. palustris confirms the hypothesis of the synthesis in these bacteria under low light conditions of other types of complexes, except LH4, which is due to the multiple biosynthesis genes of αß-polypeptides and the possibility of their various combinations.

Membrane-Bound Bacteriophytochrome-Like Complex of Phototrophic Purple Non-Sulfur Bacterium Rhodopseudomonas palustris.

A pigment-protein complex of yellow color with absorption maxima at 682 and 776 nm, characteristic for bacteriophytochromes, was isolated from the photosynthetic membranes of the purple bacterium Rhodopseudomonas palustris. Zinc-induced fluorescence of the complex indicated the presence of the biliverdin chromophore covalently bound to the protein. The parameters of low-temperature fluorescence (λ excitation at 680 nm, λ emission at 695 nm) indicated the ability of the complex to undergo photoconversion. These data, as well as the kinetics of accumulation of the red (Pr)-form on far red light, allowed the complex to be classified as a bacteriophytochrome-like complex with its localization in the photosynthetic membranes of Rps. palustris.

4-Hydroxyphenethyl alcohol--a new cytokinin-like substance from the phototrophic purple bacterium Rhodospirillum rubrum 1R.

Three compounds with cytokinin activity have been isolated from the medium of Rhodospirillum rubrum grown photosynthetically. Two N-6 aminopurine cytokinins revealed in the medium were identical with those obtained from R. rubrum cells previously. The third compound with cytokinin activity in Amaranthus caudatus bioassay proved to be a simple phenolic compound with elemental composition C8H10O2. This cytokinin-like substance according to absorption spectra, mass spectrometry and 1H NMR spectra data was identified as 4-hydroxyphenethyl alcohol.