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 αβ-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 αβ-polypeptides and the possibility of their various combinations.