Characterization of Rhodospirillum centenum and Other Novel Anoxyphototrophs

耐热固氮菌Rhodspirillum centenum于1987年分离，在光合原核生物中是独一无二的，它能产生干燥和耐热的胞囊。百年红螺菌是目前已知的唯一一种易于进行遗传和分子生物学分析的红螺菌。目前已分离出100多个具有光合代谢缺陷的突变体，这些突变体将作为一个主要目标的一部分进行生化表征，即绘制这种生物的光合作用基因的顺序。基因序列的确定将为未来关于“光化学反应中心”的工作和评估“横向基因转移”在光合作用系统进化中的可能意义提供重要的数据。控制光合作用基因的表达也将被研究，特别是关于分子氧的影响。由于越来越多的不寻常表型的可获得性为研究一些基本问题提供了有价值的实验系统，寻找以前未知的非产氧光合细菌的生物型将继续使用各种选择性浓缩和其他程序。产氧光合细菌广泛分布于自然界，并已从各种生态位中分离出来。在某些地区，它们已被确定为有机质的初级生产者，它们是各种地球化学循环中的重要催化剂。它们还成为分析所有类型的光合作用有机体中能量转换的基本机制的杰出实验系统。破译这些生物之间的进化关系是很重要的。利用经典遗传学和分子生物学，这些关系将与最近发现的细菌--百分红螺菌--一起探索。

The thermotolerant nitrogen-fixing bacterium Rhodospirillum centenum, isolated in 1987, is unique among photosynthetic prokaryotes in that it produces desiccation- and heat- resistant cysts. R. centenum is the only Rhodospirillum species known to be amenable to facile genetic and molecular biological analysis. More than 100 mutants with defects in photosynthetic metabolism have been isolated, and these will be characterized biochemically as part of a major objective, namely, mapping the order of the photosynthesis genes of this organism. Determination of the gene order will provide data of importance for future work on "photochemical reaction centers" and for assessing the possible significance of "lateral gene transfer" in the evolution of photosynthetic systems. Control of expression of photosynthesis genes in R. centenum will also be investigated, especially in regard to effects of molecular oxygen. Because the availability of an increased range of unusual phenotypes provides experimental systems of value for study of a number of fundamental problems, searches for previously unknown biotypes of non- oxygenic photosynthetic bacteria will continue using various selective enrichment and other procedures. Anoxygenic photosynthetic bacteria are widely distributed in nature and have been isolated from a great variety of ecological niches. In certain locales they have been identified as primary producers of organic matter and they are prominent catalysts in various geochemical cycles. They have also emerged as outstanding experimental systems for analysis of the basic mechanisms of energy conversion in all types of photosynthetic organisms. It is important to decipher the evolutionary relationships between these organisms. Using both classical genetics and molecular biology, these relationships will be explored with the recently discovered bacterium, Rhodospirillum centenum.