Studies on the Plasmid of Photosynthetic Bacterium Rhodospirillum rubrum

光合作用细菌红色红螺菌是一种紫色非硫细菌。在厌氧光照条件下，它们可以进行光合作用，而在好氧条件下，它们不能进行光合作用，只能异养生长。此外，在厌氧黑暗条件下，它们可以在发酵产生的三磷酸腺苷的供应下生长。在目前的研究过程中发现，在菌落中呈紫色的红色红曲霉细胞在吖黄素处理时，在肉汤琼脂上出现了各种类型的色素：白色、粉红色、淡橙色和肉色。白色(菌落)变异体表明，虽然野生型菌株携带有质粒，但由于细胞中没有作为光合色素的细菌叶绿素和类胡萝卜素，也没有必须含有光合作用机制的生色团，所以即使在任何条件下也不能进行光合作用。数据表明，该质粒大小约为50千碱基PAI。用分离到的质粒DNA转化白色突变体后，转化子恢复了光合色素的合成和绿假单胞菌的形成。当然，转移者能够进行光合作用。

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.