Mackenzie C, Choudhary M, Larimer F W, Predki P F, Stilwagen S, Armitage J P, Barber R D, Donohue T J, Hosler J P, Newman J E, Shapleigh J P, Sockett R E, Zeilstra-Ryalls J, Kaplan S
Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School, 6431 Fannin St., Houston, TX 77030, USA.
Photosynth Res. 2001;70(1):19-41. doi: 10.1023/A:1013831823701.
Rhodobacter sphaeroides 2.4.1 is an alpha-3 purple nonsulfur eubacterium with an extensive metabolic repertoire. Under anaerobic conditions, it is able to grow by photosynthesis, respiration and fermentation. Photosynthesis may be photoheterotrophic using organic compounds as both a carbon and a reducing source, or photoautotrophic using carbon dioxide as the sole carbon source and hydrogen as the source of reducing power. In addition, R. sphaeroides can grow both chemoheterotrophically and chemoautotrophically. The structural components of this metabolically diverse organism and their modes of integrated regulation are encoded by a genome of approximately 4.5 Mb in size. The genome comprises two chromosomes CI and CII (2.9 and 0.9 Mb, respectively) and five other replicons. Sequencing of the genome has been carried out by two groups, the Joint Genome Institute, which carried out shotgun-sequencing of the entire genome and The University of Texas-Houston Medical School, which carried out a targeted sequencing strategy of CII. Here we describe our current understanding of the genome when data from both of these groups are combined. Previous work had suggested that the two chromosomes are equal partners sharing responsibilities for fundamental cellular processes. This view has been reinforced by our preliminary analysis of the virtually completed genome sequence. We also have some evidence to suggest that two of the plasmids, pRS241a and pRS241b encode chromosomal type functions and their role may be more than that of accessory elements, perhaps representing replicons in a transition state.
球形红细菌2.4.1是一种α-3紫色非硫真细菌，具有广泛的代谢功能。在厌氧条件下，它能够通过光合作用、呼吸作用和发酵进行生长。光合作用可以是利用有机化合物作为碳源和还原源的光能异养型，或者利用二氧化碳作为唯一碳源、氢气作为还原力来源的光能自养型。此外，球形红细菌还能以化能异养和化能自养的方式生长。这种代谢多样的生物体的结构组成部分及其整合调控模式由一个大小约为4.5 Mb的基因组编码。该基因组由两条染色体CI和CII（分别为2.9 Mb和0.9 Mb）以及其他五个复制子组成。基因组测序工作由两个团队完成，联合基因组研究所对整个基因组进行了鸟枪法测序，德克萨斯大学休斯顿医学院则对CII进行了靶向测序策略。在此，我们结合这两个团队的数据来描述我们目前对该基因组的理解。先前的研究表明，这两条染色体是平等的伙伴，共同承担基本细胞过程的责任。我们对几乎完成的基因组序列的初步分析进一步强化了这一观点。我们也有一些证据表明，其中两个质粒pRS241a和pRS241b编码染色体类型的功能，它们的作用可能不仅仅是辅助元件，也许代表处于过渡状态的复制子。
