Studies on the Plasmid of Photosynthetic Bacterium Rhodospirillum rubrum

光合细菌红螺旋菌是一种紫色无硫细菌。在厌氧光照条件下，它们可以进行光合作用，而在好氧光照条件下，它们不能进行光合作用，只能异养生长。此外，在厌氧黑暗的条件下，它们可以在发酵提供ATP的情况下生长。也就是说，红豆杉在各种环境下都能适应生存，这对研究生物界的代谢进化具有重要意义。在本研究的过程中发现，用吖啶黄素（一种吖啶类染料）处理集落呈紫色的红小檗细胞，在肉汤琼脂培养基上出现各种类型的色素沉着；白色，粉红色，淡橙色和肉色。白色（菌落）变异表明，它们没有质粒，而野生型菌株携带质粒，即使在任何条件下也不能进行光合作用，因为它们没有细菌、叶绿素和类胡萝卜素作为光合色素，也没有细胞中必须包含光合机制的色素团。将分离得到的质粒用各种限制性内切酶进行酶切，绘制限制性内切酶图谱并估计其大小。数据表明，质粒大小约为50千碱基对。用分离的质粒dna对白色突变体进行转化后，其光合色素合成能力和叶绿体形成能力得以恢复。当然，转移体能够进行光合作用。

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.