Evolutionary Diversification of Photosynthesis and the Anoxygenic to Oxygenic Transition

Drs。J. Touchman（亚利桑那州立大学），R. Blankenship（华盛顿州立大学）和M. Madigan（南伊利诺伊大学）正在进行5种光合作用原核生物的基因组测序和代谢分析。该项目选择的生物体提供了比现在更广泛的光养分类群基因组覆盖范围。该项目的总体目标是利用基因组数据来了解光合作用的起源和进化，并探索无氧向含氧过渡的机制。被测序的生物包括生活在低温（嗜冷）、高温（嗜热）、高pH值（嗜碱）、周期性干燥环境和高硫化物环境下的物种。选择的微生物包括两种日光细菌，即卷曲日光杆菌和筋膜日光杆菌；4种变形菌，分别是南极红铁菌、全球红藻、绿芽绿藻和温染菌；和一种蓝藻，双胞菌（又名振荡菌）。变形菌包括来自β和γ分裂的成员，其中一个包含细菌叶绿素b作为其主要的光色素。完成的、带注释的基因组序列被用来填补光合作用原核生物基因组数据的巨大空白。这些生物的代谢能力也正在使用途径分析软件工具进行分析。每一种生物都有其独特的特征，包括进化关系、农业应用和环境方面，这些特征都证明了将其纳入基因组测序计划的合理性。塔奇曼参与了亚利桑那州立大学的“成为生物学家”项目。所有的研究者都让本科生和高中生在他们的实验室里进行序列分析和注释活动。

Drs. J. Touchman (Arizona State Univ), R. Blankenship (Washinton State Univ) and M. Madigan (Southern Illinois Univ.) are carrying out the genome sequencing and metabolic analysis of five photosynthetic prokaryotes. Organisms for this project were chosen to provide significantly wider coverage of genomes of phototrophic taxa than is now available. The broad goals of the project are to use the genomic data to understand the origin and evolution of photosynthesis and to explore mechanisms of the anoxygenic to oxygenic transition. The organisms being sequenced include species that live at low temperature (psychrophilic), high temperature (thermophilic), high pH (alkaliphilic), in environments subject to periodic drying, and environments high in sulfide. The organisms chosen include two heliobacteria, Heliorestis convoluta and Heliophilum fasciatum; four proteobacteria, Rhodoferax antarcticus, Rhodopila globiformis, Blastochloris viridis, and Thermochromatium tepidum; and one cyanobacterium, Leptolyngbya (a.k.a. Oscillatoria) amphigranulata. The proteobacteria include members from the beta and gamma divisions and one that contains bacteriochlorophyll b as its principal photopigment. The finished, annotated genome sequences are being used to fill large gaps in the available genomic data for photosynthetic prokaryotes. The metabolic capabilities of these organisms are also being analyzed using pathway analysis software tools. Each organism has individual characteristics that justify its inclusion in a genome-sequencing project, including evolutionary relationships, agricultural applications and environmental aspects.Dr. Touchman is involved in the Be a Biologist program at ASU. All of the investigators are involving undergraduate and high school students in sequence analysis and annotation activities in their labs.