State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
School of Life Science, Qilu Normal University, Jinan, China.
Appl Environ Microbiol. 2020 May 19;86(11). doi: 10.1128/AEM.00242-20.
The type IX secretion system (T9SS), which is involved in pathogenicity, motility, and utilization of complex biopolymers, is a novel protein secretion system confined to the phylum , a common cellulolytic soil bacterium belonging to the phylum , can rapidly digest crystalline cellulose using a novel strategy. In this study, the deletion mutant of () was obtained using PY6 medium supplemented with Stanier salts. GldN was verified to be a core component of T9SS, and is indispensable for cellulose degradation, motility, and secretion of C-terminal domain (CTD) proteins. Notably, the Δ mutant showed significant growth defects in Ca- and Mg-deficient media. These growth defects could be relieved by the addition of Ca or Mg The intracellular concentrations of Ca and Mg were markedly reduced in Δ These results demonstrated that GldN is essential for the acquisition of trace amounts of Ca and Mg, especially for Ca Moreover, an outer membrane efflux protein, CHU_2807, which was decreased in abundance on the outer membrane of Δ, is essential for normal growth in PY6 medium. The reduced intracellular accumulation of Ca and Mg in the Δ mutant indicated that CHU_2807 is involved in the uptake of trace amounts of Ca and Mg This study provides insights into the role of T9SS in metal ion assimilation in The widespread Gram-negative bacterium uses a novel but poorly understood strategy to utilize crystalline cellulose. Recent studies showed that a T9SS exists in and is involved in cellulose degradation and motility. However, the main components of the T9SS and their functions are still unclear. Our study characterized the function of GldN, which is a core component of the T9SS. GldN was proved to play vital roles in cellulose degradation and cell motility. Notably, GldN is essential for the acquisition of Ca and Mg ions under Ca- and Mg-deficient conditions, revealing a link between the T9SS and the metal ion transport system. The outer membrane abundance of CHU_2807, which is essential for Ca and Mg uptake in PY6 medium, was affected by the deletion of GldN. This study demonstrated that the T9SS has extensive functions, including cellulose degradation, motility, and metal ion assimilation, and contributes to further understanding of the function of the T9SS in the phylum .
IX 型分泌系统（T9SS）参与致病性、运动性和复杂生物聚合物的利用，是一种新型蛋白分泌系统，局限于 门，是一种常见的纤维素分解土壤细菌，属于 门，可以使用一种新策略快速消化结晶纤维素。在这项研究中，使用补充了 Stanier 盐的 PY6 培养基获得了 ()的缺失突变体。GldN 被验证为 T9SS 的核心组成部分，对于纤维素降解、运动性和 C 端结构域（CTD）蛋白的分泌是必不可少的。值得注意的是，Δ突变体在缺钙和缺镁的培养基中表现出明显的生长缺陷。这些生长缺陷可以通过添加 Ca 或 Mg 得到缓解。Δ突变体细胞内 Ca 和 Mg 的浓度明显降低。这些结果表明 GldN 对于获取痕量的 Ca 和 Mg 是必不可少的，特别是对于 Ca。此外，一种外膜外排蛋白 CHU_2807，在 Δ的外膜上丰度降低，对于在 PY6 培养基中的正常生长是必不可少的。Δ突变体中 Ca 和 Mg 的细胞内积累减少表明 CHU_2807 参与了痕量 Ca 和 Mg 的摄取。这项研究深入了解了 T9SS 在 金属离子吸收中的作用。广泛存在的革兰氏阴性菌 使用一种新颖但知之甚少的策略来利用结晶纤维素。最近的研究表明，T9SS 存在于 中，参与纤维素的降解和运动性。然而， T9SS 的主要成分及其功能仍不清楚。我们的研究描述了 GldN 的功能，GldN 是 T9SS 的核心组成部分。GldN 被证明在纤维素降解和细胞运动中起着至关重要的作用。值得注意的是，GldN 对于在缺钙和缺镁条件下获取 Ca 和 Mg 离子是必不可少的，这揭示了 T9SS 与金属离子转运系统之间的联系。CHU_2807 的外膜丰度在外膜缺失时受到影响，在 PY6 培养基中对于 Ca 和 Mg 的摄取是必不可少的。这项研究表明， T9SS 具有广泛的功能，包括纤维素降解、运动性和金属离子同化，并有助于进一步了解 T9SS 在 门中的功能。
