Identification and Subcellular Distribution of Carotenoids in the Aerobic Photosynthetic Bacterium,Pseudomonas radioraStrain MD-1

摘要

The carotenoid compositions in the aerobic methylotrophic photosynthetic bacterium,Pseudomonas radiora (Methylobacterium radiotolerans) strain MD-1, were investigated. Carotenoids bound to the BChl-protein complex were identified as spirilloxanthin, anhydrorhodovibrin and rhodovibrin, which have been generally found in purple photosynthetic bacteria. The ratio of BChlato carotenoid in the BChl-protein complex was about 2 to 1. The transfer of excitation energy from carotenoids to BChl in the BChl-protein complex was observed although its efficiency was as low as that in the purple bacterial complexes which have spirilloxanthin as the major carotenoid component. By contrast, carotenoic acids were found as major forms of carotenoids in the cells, and most of them were not bound to the BChl-protein complex. These carotenoic acids were also found as the major carotenoids in other methylotrophs that have been characterized as aerobic photosynthetic bacteria.