The cell biology of Chloroflexota is poorly studied. We applied cryo-focused ion beam milling and cryo-electron tomography to study the ultrastructural organization of thermophilic Roseiflexus castenholzii and Chloroflexus aggregans, and mesophilic “Ca. Viridilinea mediisalina.” These species represent the three main lineages within a group of multicellular filamentous anoxygenic phototrophic Chloroflexota bacteria belonging to the Chloroflexales order. We found surprising structural complexity in the Chloroflexales. As with filamentous cyanobacteria, cells of C. aggregans and “Ca. Viridilinea mediisalina” share the outer membrane-like layers of their intricate multilayer cell envelope. Additionally, cells of R. castenholzii and “Ca. Viridilinea mediisalina” are connected by septal channels that resemble cyanobacterial septal junctions. All three strains possess long pili anchored close to cell-to-cell junctions, a morphological feature comparable to that observed in cyanobacteria. The cytoplasm of the Chloroflexales bacteria is crowded with intracellular organelles such as different types of storage granules, membrane vesicles, chlorosomes, gas vesicles, chemoreceptor-like arrays, and cytoplasmic filaments. We observed a higher level of complexity in the mesophilic strain compared to the thermophilic strains with regards to the composition of intracellular bodies and the organization of the cell envelope. The ultrastructural details that we describe in these Chloroflexales bacteria will motivate further cell biological studies, given that the function and evolution of the many discovered morphological traits remain enigmatic in this diverse and widespread bacterial group.

的细胞生物学 绿弯曲菌研究不多。我们应用了低温聚焦离子束铣削和低温电子断层扫描技术来研究嗜热的超微结构玫瑰蔷薇 和 绿叶绿豆和中温的“钙。Viridilinea mediisalina。” 这些物种代表一组多细胞丝状产氧光养性的三个主要谱系绿弯曲菌 属于 叶绿藻订购。我们发现令人惊讶的结构复杂性叶绿藻。与丝状蓝细菌一样，C.agregans 和“钙。Viridilinea mediisalina”共享复杂的多层细胞包膜的外膜状层。此外，R. castenholzii 和“钙。“ Viridilinea mediisalina”通过类似于蓝细菌隔膜连接处的隔膜通道连接。所有三个菌株都具有长的菌毛，锚定在细胞间连接附近，其形态特征与蓝细菌中观察到的相当。的细胞质叶绿藻细菌挤满了细胞内的细胞器，例如不同类型的储存颗粒，膜囊泡，氯脂质体，气体囊泡，化学感受器样阵列和细胞质细丝。就细胞内体的组成和细胞包膜的组织而言，我们发现与嗜热菌株相比，嗜温菌株的复杂性更高。我们在这些文章中描述的超微结构细节叶绿藻 鉴于许多已发现的形态学特征的功能和进化在这个多样而广泛的细菌群中仍然是未知的，细菌将激发进一步的细胞生物学研究。