Department of Biology and Department of Chemistry, Campus Box 1137, Washington University in St. Louis, St. Louis, MO 63130, USA.
BMC Genomics. 2011 Jun 29;12:334. doi: 10.1186/1471-2164-12-334.
Chloroflexus aurantiacus is a thermophilic filamentous anoxygenic phototrophic (FAP) bacterium, and can grow phototrophically under anaerobic conditions or chemotrophically under aerobic and dark conditions. According to 16S rRNA analysis, Chloroflexi species are the earliest branching bacteria capable of photosynthesis, and Cfl. aurantiacus has been long regarded as a key organism to resolve the obscurity of the origin and early evolution of photosynthesis. Cfl. aurantiacus contains a chimeric photosystem that comprises some characters of green sulfur bacteria and purple photosynthetic bacteria, and also has some unique electron transport proteins compared to other photosynthetic bacteria.
The complete genomic sequence of Cfl. aurantiacus has been determined, analyzed and compared to the genomes of other photosynthetic bacteria.
Abundant genomic evidence suggests that there have been numerous gene adaptations/replacements in Cfl. aurantiacus to facilitate life under both anaerobic and aerobic conditions, including duplicate genes and gene clusters for the alternative complex III (ACIII), auracyanin and NADH:quinone oxidoreductase; and several aerobic/anaerobic enzyme pairs in central carbon metabolism and tetrapyrroles and nucleic acids biosynthesis. Overall, genomic information is consistent with a high tolerance for oxygen that has been reported in the growth of Cfl. aurantiacus. Genes for the chimeric photosystem, photosynthetic electron transport chain, the 3-hydroxypropionate autotrophic carbon fixation cycle, CO2-anaplerotic pathways, glyoxylate cycle, and sulfur reduction pathway are present. The central carbon metabolism and sulfur assimilation pathways in Cfl. aurantiacus are discussed. Some features of the Cfl. aurantiacus genome are compared with those of the Roseiflexus castenholzii genome. Roseiflexus castenholzii is a recently characterized FAP bacterium and phylogenetically closely related to Cfl. aurantiacus. According to previous reports and the genomic information, perspectives of Cfl. aurantiacus in the evolution of photosynthesis are also discussed.
The genomic analyses presented in this report, along with previous physiological, ecological and biochemical studies, indicate that the anoxygenic phototroph Cfl. aurantiacus has many interesting and certain unique features in its metabolic pathways. The complete genome may also shed light on possible evolutionary connections of photosynthesis.
黄化着色菌（Chloroflexus aurantiacus）是一种嗜热丝状厌氧型光合（FAP）细菌，能够在厌氧条件下进行光养生长，或在有氧黑暗条件下进行化能异养生长。根据 16S rRNA 分析，Chloroflexi 物种是最早能够进行光合作用的分支细菌，而 Cfl. aurantiacus 长期以来一直被认为是解决光合作用起源和早期进化之谜的关键生物。Cfl. aurantiacus 含有一种嵌合光合作用系统，包含一些绿硫细菌和紫细菌的特征，与其他光合细菌相比，它还具有一些独特的电子传递蛋白。
已经确定、分析并比较了 Cfl. aurantiacus 的完整基因组序列，以及其他光合细菌的基因组。
丰富的基因组证据表明，Cfl. aurantiacus 中发生了大量的基因适应/替换，以促进其在厌氧和有氧条件下的生存，包括用于替代复合物 III（ACIII）、auracyanin 和 NADH：醌氧化还原酶的重复基因和基因簇；以及中央碳代谢和四吡咯类和核酸生物合成中几种好氧/厌氧酶对。总的来说，基因组信息与 Cfl. aurantiacus 生长过程中报道的高耐氧性一致。嵌合光合作用系统、光合作用电子传递链、3-羟基丙酸自养碳固定循环、CO2 同化途径、乙醛酸循环和硫还原途径的基因都存在。讨论了 Cfl. aurantiacus 的中心碳代谢和硫同化途径。还将 Cfl. aurantiacus 的基因组与最近被描述的 FAP 细菌玫瑰色红杆菌（Roseiflexus castenholzii）的基因组进行了比较。Roseiflexus castenholzii 是一种最近被描述的 FAP 细菌，与 Cfl. aurantiacus 亲缘关系密切。根据之前的报道和基因组信息，还讨论了 Cfl. aurantiacus 在光合作用进化中的观点。
本报告中的基因组分析，以及之前的生理、生态和生化研究，表明厌氧型光养生物 Cfl. aurantiacus 在其代谢途径中具有许多有趣和独特的特征。完整的基因组也可能揭示光合作用可能的进化联系。
