Flaugnatti Nicolas, Bader Loriane, Croisier-Coeytaux Mary, Blokesch Melanie
Laboratory of Molecular Microbiology, Global Health Institute, School of Life Sciences, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Bioelectron Microscopy Core Facility, School of Life Sciences, Station 19, EPFL-SV-PTBIOEM, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Elife. 2025 Jan 3;14:e101032. doi: 10.7554/eLife.101032.
The type VI secretion system (T6SS) is a sophisticated, contact-dependent nanomachine involved in interbacterial competition. To function effectively, the T6SS must penetrate the membranes of both attacker and target bacteria. Structures associated with the cell envelope, like polysaccharides chains, can therefore introduce spatial separation and steric hindrance, potentially affecting the efficacy of the T6SS. In this study, we examined how the capsular polysaccharide (CPS) of affects T6SS's antibacterial function. Our findings show that the CPS confers resistance against T6SS-mediated assaults from rival bacteria. Notably, under typical growth conditions, the presence of the surface-bound capsule also reduces the efficacy of the bacterium's own T6SS. This T6SS impairment is further enhanced when CPS is overproduced due to genetic modifications or antibiotic treatment. Furthermore, we demonstrate that the bacterium adjusts the level of the T6SS inner tube protein Hcp according to its secretion capacity, by initiating a degradation process involving the ClpXP protease. Collectively, our findings contribute to a better understanding of the dynamic relationship between T6SS and CPS and how they respond swiftly to environmental challenges.
VI型分泌系统（T6SS）是一种复杂的、依赖接触的纳米机器，参与细菌间的竞争。为了有效发挥作用，T6SS必须穿透攻击菌和靶细菌的膜。因此，与细胞壁相关的结构，如多糖链，会造成空间分离和空间位阻，可能影响T6SS的功效。在本研究中，我们研究了 的荚膜多糖（CPS）如何影响T6SS的抗菌功能。我们的研究结果表明，CPS赋予细菌抵抗来自竞争细菌的T6SS介导攻击的能力。值得注意的是，在典型的生长条件下，表面结合的荚膜的存在也会降低细菌自身T6SS的功效。当由于基因改造或抗生素处理导致CPS过量产生时，这种T6SS损伤会进一步加剧。此外，我们证明细菌通过启动一个涉及ClpXP蛋白酶的降解过程，根据其分泌能力调节T6SS内管蛋白Hcp的水平。总的来说，我们的研究结果有助于更好地理解T6SS和CPS之间的动态关系，以及它们如何迅速应对环境挑战。
