Compositional Analysis of Carotenoids in a Purple Photosynthetic Bacteria, Rhodopseudomonas sp. Strain Rits, upon Irradiated Light Intensity

Abstract

Recently we isolated a purple photo- synthetic bacterium Rhodopseudomonas (Rps.) sp. strain Rits which is phylogenetically close to Rps. palustris. Under low-light conditions, this strain biosynthesized an unusual peripheral antenna (LH4) at the expense of the usual LH2. In this study, we analyzed the composition of carotenoids from the Rits strain together with Rps. palustris that were grown by irradiation of different light intensity. All seven carotenoids of spirilloxan- thin biosynthetic pathway (lycopene, rhodopin, 3,4-didehydrorhodopin, anhydrorhodovibrin, rho- dovibrin, OH-spirilloxanthin, spirilloxanthin) were clearly detected by high-resolution normal-phase HPLC. In the extract from the cells, 3,4-didehy- drorhodopin having 12 conjugated double bonds as well as one terminal hydroxy group was a major carotenoid under normal- and high-light conditions, while rhodopin having 11 conjugated double bond as well as one terminal hydroxy group was a major component under low-light conditions. 3,4-Didehydrorhodopin was found to be first accumulated at a significant amount in Rps. species including the Rits strain and Rps. palustris CGA009/DSM123.