Genetics and Photophysiology of Novel Anoxyphototrophs

最近发现的非硫紫色光合细菌centenum红螺旋菌表现出一些以前在光合真细菌中未知的生理特性。其中一个特征是存在一个生命周期，涉及形成耐热和耐干燥的囊肿。Rsp的萌发。centum囊肿导致细胞分化，其特征是在固体培养基上的群体细胞行为。在固体琼脂培养基上生长的群细胞有许多侧鞭毛，与具有单极鞭毛的非群细胞不同。群体细胞分化似乎是生命周期的一个阶段，是对介质粘度增加的一种特殊反应。Rsp的第二个不同寻常的特性。百聚体是指蜂群细胞群体具有快速迁移的能力，要么向光移动，要么远离光；观测到的速率高达45毫米/小时。作用谱表明585 nm的光排斥，而800-880 nm的光吸引。本研究的主要目标包括群体细胞的生理特征以及Rsp的趋光行为分析。centenum。此外，将对群体细胞形成和趋光性进行遗传分析，以确定参与这些过程的遗传位点的数量和性质。这些研究也将通过所涉及的光感受器的生化和分子遗传学特征来增强。预计该研究将为原核细胞分化提供重要信息，并首次对真细菌的趋光性机制进行分子分析。我们还建议将细菌光合作用的遗传分析扩展到进化上不同种类的真细菌光养生物。本研究领域的目的是获得从温绿绿杆菌、绿黑杆菌、绿红假单胞菌和蓝藻中获得的细菌叶绿素生物合成基因的克隆，以确定光合作用基因簇在不同属和种的光合原核生物中的保守程度。获得的克隆还将用于对细菌和植物叶绿素生物合成途径共有的遗传位点进行序列分析，用于植物系统中叶绿素生物合成的后续研究。＊＊＊

9303836 Bauer The recently described nonsulfur purple photosynthetic bacterium Rhodospirillum centenum exhibits several physiological traits previously unknown among photosynthetic eubacteria. One feature is the existence of a life cycle involving the formation of heat and desiccation resistant cysts. Germination of Rsp. centenum cysts leads to cell differentiation characterized by swarm cell behavior on solid media. Swarm cells grown on solid agar medium have numerous lateral flagella and are distinct from non-swarm cells which bear a single polar flagellum. Swarm cell differentiation appears to be a stage of a life cycle and to be a specific response to an increase in medium viscosity. A second unusual feature of Rsp. centenum is that swarm cell colonies have the capacity to migrate rapidly either towards or away from light; rates as high as 45 mm/hour have been observed. An action spectrum has demonstrated that 585 nm light repels whereas light over the region 800-880 nm attracts. Major goals of this proposal include the physiological characterization of swarm cells as well as an analysis of phototactic behavior of Rsp. centenum. In addition, genetic analyses of swarm cell formation as well as phototaxis will be undertaken to determine the number and nature of the genetic loci involved in these processes. These studies will also be augmented by biochemical and molecular genetic characterization of the photoreceptor(s) involved. It is anticipated that the proposed research will provide significant information on prokaryotic cell differentiation and in addition, should provide the first molecular analysis of the mechanism of phototaxis in eubacteria. We also propose to extend genetic analysis of bacterial photosynthesis to evolutionarily divers species of eubacterial phototrophs. The aim of this area of research is to obtain clones of bacteriochlorophyll biosynthesis genes from Chlorobium tepidum, Heliobacterium gestii, Rhodopseudomonas viridis and cyanobacteria for the purpose of determining the extent to which a Photosynthesis Gene Cluster is conserved among various genera and species of phototrophic prokaryotes. The clones obtained will also be used to generate sequence analyses of genetic loci common to bacterial and plant chlorophyll biosynthetic pathways for use in subsequent studies of chlorophyll biosynthesis in plant systems. ***