Louvain Institute of Biomolecular Science and Technology, Biochemistry and Genetics of Microorganisms, Université catholique de Louvain, Louvain-La-Neuve, Belgium.
Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausannegrid.9851.5, Lausanne, Switzerland.
mSystems. 2022 Dec 20;7(6):e0073522. doi: 10.1128/msystems.00735-22. Epub 2022 Nov 7.
Competence is one of the most efficient bacterial evolutionary and adaptative strategies by synchronizing production of antibacterial compounds and integration of DNA released by dead cells. In most streptococci, this tactic is orchestrated by the ComRS system, a pheromone communication device providing a short time window of activation in which only part of the population is responsive. Understanding how this developmental process integrates multiple inputs to fine-tune the adequate response is a long-standing question. However, essential genes involved in the regulation of ComRS have been challenging to study. In this work, we built a conditional mutant library using CRISPR interference and performed three complementary screens to investigate competence genetic regulation in the human commensal Streptococcus salivarius. We show that initiation of competence increases upon cell wall impairment, suggesting a connection between cell envelope stress and competence activation. Notably, we report a key role for StkP, a serine-threonine kinase known to regulate cell wall homeostasis. We show that StkP controls competence by a mechanism that reacts to peptidoglycan fragments. Together, our data suggest a key cell wall sensing mechanism coupling competence to cell envelope integrity. Survival of human commensal streptococci in the digestive tract requires efficient strategies which must be tightly and collectively controlled for responding to competitive pressure and drastic environmental changes. In this context, the autocrine signaling system ComRS controlling competence for natural transformation and predation in salivarius streptococci could be seen as a multi-input device integrating a variety of environmental stimuli. In this work, we revealed novel positive and negative competence modulators by using a genome-wide CRISPR interference strategy. Notably, we highlighted an unexpected connection between bacterial envelope integrity and competence activation that involves several cell wall sensors. Together, these results showcase how commensal streptococci can fine-tune the pheromone-based competence system by responding to multiple inputs affecting their physiological status in order to calibrate an appropriate collective behavior.
适能是一种最有效的细菌进化和适应策略，通过协调抗菌化合物的产生和死细胞释放的 DNA 的整合。在大多数链球菌中，这种策略是由 ComRS 系统协调的，这是一种信息素通讯装置，提供了一个短暂的激活时间窗口，只有部分种群对此有反应。了解这个发育过程如何整合多个输入以微调适当的反应是一个长期存在的问题。然而，涉及 ComRS 调节的必需基因一直是研究的难点。在这项工作中，我们使用 CRISPR 干扰构建了一个条件性突变体文库，并进行了三次互补筛选，以研究人类共生链球菌唾液链球菌中的适能遗传调控。我们发现，细胞壁受损会增加适能的起始，这表明细胞包膜应激和适能激活之间存在联系。值得注意的是，我们报告了丝氨酸-苏氨酸激酶 StkP 的关键作用，StkP 已知可以调节细胞壁的稳态。我们发现，StkP 通过一种对肽聚糖片段作出反应的机制来控制适能。总的来说，我们的数据表明，一种关键的细胞壁感应机制将适能与细胞包膜完整性联系起来。
人类共生链球菌在消化道中的生存需要有效的策略，这些策略必须紧密而集体地控制，以应对竞争压力和剧烈的环境变化。在这种情况下，自分泌信号系统 ComRS 控制着唾液链球菌自然转化和捕食的适能，可以被视为一种整合了多种环境刺激的多输入装置。在这项工作中，我们使用全基因组 CRISPR 干扰策略揭示了新的正、负适能调节剂。值得注意的是，我们发现了细菌包膜完整性和适能激活之间的一个意外联系，这涉及到几种细胞壁传感器。总的来说，这些结果展示了共生链球菌如何通过响应影响其生理状态的多个输入来微调基于信息素的适能系统，从而校准适当的集体行为。
