Grossman Alex S, Lei Lei, Botting Jack M, Liu Jett, Nahar Nusrat, Souza João Gabriel S, Liu Jun, McLean Jeffrey S, He Xuesong, Bor Batbileg
Department of Microbiology, ADA Forsyth Institute, Cambridge MA, 02142, USA.
West China Hospital of Stomatology, Sichuan University, Chengdu Sichuan, 610093, China.
bioRxiv. 2024 Nov 25:2024.11.25.624915. doi: 10.1101/2024.11.25.624915.
All cultivated Patescibacteria, or CPR, exist as obligate episymbionts on other microbes. Despite being ubiquitous in mammals and environmentally, molecular mechanisms of host identification and binding amongst ultrasmall bacterial episymbionts are largely unknown. Type 4 pili (T4P) are well conserved in this group and predicted to facilitate symbiotic interactions. To test this, we targeted T4P pilin genes in Saccharibacteria strain TM7x to assess their essentiality and roles in symbiosis. Our results revealed that assembles two distinct T4P, a non-essential thin pili that has the smallest diameter of any T4P and contributes to host-binding, episymbiont growth, and competitive fitness relative to other Saccharibacteria, and an essential thick pili whose functions include twitching motility. Identification of lectin-like minor pilins and modification of host cell walls suggest glycan binding mechanisms. Collectively our findings demonstrate that Saccharibacteria encode unique extracellular pili that are vital mediators of their underexplored episymbiotic lifestyle.
所有培养的狭性杆菌（Patescibacteria），即 CPR，均作为其他微生物上的专性外共生体存在。尽管在哺乳动物和环境中普遍存在，但超小型细菌外共生体之间宿主识别和结合的分子机制在很大程度上仍不清楚。4 型菌毛（T4P）在该类群中高度保守，并被预测有助于共生相互作用。为了验证这一点，我们靶向糖杆菌属菌株 TM7x 中的 T4P 菌毛蛋白基因，以评估它们在共生中的必要性和作用。我们的结果表明，它组装了两种不同的 T4P，一种非必需的细菌毛，其直径是所有 T4P 中最小的，有助于宿主结合、外共生体生长以及相对于其他糖杆菌的竞争适应性，还有一种必需的粗菌毛，其功能包括颤动运动。凝集素样小菌毛蛋白的鉴定和宿主细胞壁的修饰表明存在聚糖结合机制。我们的研究结果共同表明，糖杆菌编码独特的细胞外菌毛，这些菌毛是其尚未充分探索的外共生生活方式的重要介质。
