Table_2_Whither the genus Caldicellulosiruptor and the order Thermoanaerobacterales: phylogeny, taxonomy, ecology, and phenotype.XLSX

The order Thermoanaerobacterales currently consists of fermentative anaerobic bacteria, including the genus Caldicellulosiruptor. Caldicellulosiruptor are represented by thirteen species; all, but one, have closed genome sequences. Interest in these extreme thermophiles has been motivated not only by their high optimal growth temperatures (≥70°C), but also by their ability to hydrolyze polysaccharides including, for some species, both xylan and microcrystalline cellulose. Caldicellulosiruptor species have been isolated from geographically diverse thermal terrestrial environments located in New Zealand, China, Russia, Iceland and North America. Evidence of their presence in other terrestrial locations is apparent from metagenomic signatures, including volcanic ash in permafrost. Here, phylogeny and taxonomy of the genus Caldicellulosiruptor was re-examined in light of new genome sequences. Based on genome analysis of 15 strains, a new order, Caldicellulosiruptorales, is proposed containing the family Caldicellulosiruptoraceae, consisting of two genera, Caldicellulosiruptor and Anaerocellum. Furthermore, the order Thermoanaerobacterales also was re-assessed, using 91 genome-sequenced strains, and should now include the family Thermoanaerobacteraceae containing the genera Thermoanaerobacter, Thermoanaerobacterium, Caldanaerobacter, the family Caldanaerobiaceae containing the genus Caldanaerobius, and the family Calorimonaceae containing the genus Calorimonas. A main outcome of ANI/AAI analysis indicates the need to reclassify several previously designated species in the Thermoanaerobacterales and Caldicellulosiruptorales by condensing them into strains of single species. Comparative genomics of carbohydrate-active enzyme inventories suggested differentiating phenotypic features, even among strains of the same species, reflecting available nutrients and ecological roles in their native biotopes.

Thermoanaerobacterales这一序列目前包含发酵性厌氧细菌，其中包含Caldicellulosiruptor属。Caldicellulosiruptor属由十三种物种构成，其中除了一种之外，其余均已具有封闭的基因组序列。对这些极端嗜热微生物的兴趣不仅源于其高最适生长温度（≥70°C），还在于它们能够水解包括某些物种的木聚糖和微晶纤维素在内的多糖。Caldicellulosiruptor物种已被从新西兰、中国、俄罗斯、冰岛和北美等地地理分布广泛的陆地热环境中分离出来。从永久冻土层中的火山灰等元基因组特征中，可以明显看出它们在其他陆地位置的分布。在此，考虑到新的基因组序列，对Caldicellulosiruptor属的进化系统学和分类学进行了重新审视。基于15个菌株的基因组分析，提出一个新的序列Caldicellulosiruptorales，包含Caldicellulosiruptoraceae科，该科包括Caldicellulosiruptor和Anaerocellum两个属。此外，使用91个基因组测序菌株对Thermoanaerobacterales进行了重新评估，现在应包括Thermoanaerobacteraceae科，其中包含Thermoanaerobacter、Thermoanaerobacterium、Caldanaerobacter属；Caldanaerobiaceae科，其中包含Caldanaerobius属；以及Calorimonaceae科，其中包含Calorimonas属。ANI/AAI分析的主要结果表明，有必要将Thermoanaerobacterales和Caldicellulosiruptorales中先前指定的几个物种重新分类，将它们浓缩为单一物种的菌株。碳水化合物活性酶组比较基因组学揭示了不同表型特征，即使在同一物种的菌株之间也存在差异，反映了它们在原生生物群落中可获得的营养和生态角色。