School of Life Sciences, University of Nevada Las Vegas, Las Vegas, NV, 89154, USA.
State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-Sen University, 510275, Guangzhou, People's Republic of China.
ISME J. 2023 Jul;17(7):952-966. doi: 10.1038/s41396-023-01405-0. Epub 2023 Apr 11.
Although the phylum Chloroflexota is ubiquitous, its biology and evolution are poorly understood due to limited cultivability. Here, we isolated two motile, thermophilic bacteria from hot spring sediments belonging to the genus Tepidiforma and class Dehalococcoidia within the phylum Chloroflexota. A combination of cryo-electron tomography, exometabolomics, and cultivation experiments using stable isotopes of carbon revealed three unusual traits: flagellar motility, a peptidoglycan-containing cell envelope, and heterotrophic activity on aromatics and plant-associated compounds. Outside of this genus, flagellar motility has not been observed in Chloroflexota, and peptidoglycan-containing cell envelopes have not been described in Dehalococcoidia. Although these traits are unusual among cultivated Chloroflexota and Dehalococcoidia, ancestral character state reconstructions showed flagellar motility and peptidoglycan-containing cell envelopes were ancestral within the Dehalococcoidia, and subsequently lost prior to a major adaptive radiation of Dehalococcoidia into marine environments. However, despite the predominantly vertical evolutionary histories of flagellar motility and peptidoglycan biosynthesis, the evolution of enzymes for degradation of aromatics and plant-associated compounds was predominantly horizontal and complex. Together, the presence of these unusual traits in Dehalococcoidia and their evolutionary histories raise new questions about the timing and selective forces driving their successful niche expansion into global oceans.
尽管绿弯菌门无处不在，但由于其可培养性有限，其生物学和进化仍知之甚少。在这里，我们从属于绿弯菌门的热泉沉积物中分离出了两种运动的嗜热细菌，它们属于 Tepidiforma 属和 Dehalococcoidia 类。结合低温电子断层扫描、外代谢组学和使用碳稳定同位素的培养实验，揭示了三个不寻常的特征：鞭毛运动、含有肽聚糖的细胞壁和对芳烃和植物相关化合物的异养活性。在该属之外，绿弯菌门中尚未观察到鞭毛运动，而 Dehalococcoidia 中也未描述含有肽聚糖的细胞壁。尽管这些特征在培养的绿弯菌门和 Dehalococcoidia 中不常见，但祖先特征状态重建表明鞭毛运动和含有肽聚糖的细胞壁在 Dehalococcoidia 中是祖先的，随后在 Dehalococcoidia 向海洋环境的主要适应性辐射之前丢失。然而，尽管鞭毛运动和肽聚糖生物合成的进化历史主要是垂直的，但降解芳烃和植物相关化合物的酶的进化主要是水平和复杂的。总之，这些不寻常特征在 Dehalococcoidia 中的存在及其进化历史提出了关于推动它们成功扩展到全球海洋的时机和选择压力的新问题。
