LH2 complexes (B800-850 AND B800-830) are assembled in the cells of sulfur bacterium Thiorhodospira sibirica, strain Kir 3, without any carotenoids

Abstract

It has been studied the result of assembling the light-harvesting complexes in the cells of purple sulfuric bacterium Thiorhodospira (T.) sibirica, strain Kir‑3, while suppressing biosynthesis of carotenoids by diphenylamine (DPA). LH2 complexes (B800-850 and B800-830) with different carotenoids’ composition were isolated from the cells obtained. Maximal inhibition of carotenoid biosynthesis (~90% of the control) was achieved at the inhibitor concentration of 53,25 mM (9 mg/l). It has been established that changes in qualitative and quantitative composition of carotenoids do not affect the assembling of B800-830 and B800-850 complexes. It is assumed that in the population of DPA-LH2 complexes from T. sibirica, strain Kir‑3, both carotenoidless complexes and the complexes, containing one or two carotenoid molecules, can be assembled. These results support a hypothesis that carotenoids are not required for assembling B800-850 and B800-830 complexes.