Studies on the Plasmid of Photosynthetic Bacterium Rhodospirillum rubrum

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Photosynthetic bacterium Rhodospirillum rubum is a kind of purple non-sulfur bacteria. In the conditions of anaerobic lighting, they can photosynthesize, whreas in the aerobic conditions they can not do photo synthesis but can grow only heterotrophically. Further,in the conditions of anaerobic darkness, they can grow with a supply of ATP from fermentation. That is, the R, rubrum can survive adaptively under various environments and thus it is useful for studies on the metabolic evolution in the biological world.It bas found in the course of the present strdies that when the R. rubrum cells, which show purple color in the colony, was treated with acriflavine, a kind of acridine dyes, various types of pigmentations appear on a broth agar medium; White, pink,weak orange, and flesh. The white(colony) variants was demonstrated to show that they have no a plasmid although the wild type strain carry the plasmid and could not photosyhtesize even under any conditions because they have no bacterio chlorophyll and carotenoid as photosynthetic pigments and no chromatophores, which have to contain photosynthetic machineries, in the cell.Plasmid isolated was digested by various types of restriction enzymes to make the restriciton enzyme map and to estimate the size. The data showed that the plasmid size is about 50 kilobase pais. When the white mutants were transformed by plasmid dna isolated, the transformants restored abilities of syntheses of the photosynthetic pigments and of formation of chloromato phore. It is of course that the transfermants are able to photosynthesize.