Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
Department of Microbiology and Immunology, The University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
mBio. 2020 Dec 22;11(6):e03190-20. doi: 10.1128/mBio.03190-20.
The accessory gene regulator 1 () locus consists of two genes, and , that presumably constitute an autoinducing peptide (AIP) system. Typically, AIP systems function through the AgrB-mediated processing of AgrD to generate a processed form of the AIP that provides a concentration-dependent extracellular signal. Here, we show that the 630 Agr1 system has multiple functions, not all of which depend on AgrB1. CRISPR-Cas9n deletion of , a, or the entire locus resulted in changes in transcription of sporulation-related factors and an overall loss in spore formation. Sporulation was recovered in the mutants by providing supernatant from stationary-phase cultures of the parental strain. In contrast, motility was reduced only when both AgrB1 and AgrD1 were disrupted. Finally, in the absence of AgrB1, the AgrD1 peptide accumulated within the cytoplasm and this correlated with increased expression of (15-fold), as well as (20-fold) and (5-fold), which encode the two major toxins. The combined deletion of / or deletion of only did not significantly alter expression of or but did show a minor effect on expression. Overall, these data indicate that the Agr1-based system in 630 carries out multiple functions, some of which are associated with prototypical AIP signaling and others of which involve previously undescribed mechanisms of action. is a spore-forming, toxigenic, anaerobic bacterium that causes severe gastrointestinal illness. Understanding the ways in which senses growth conditions to regulate toxin expression and sporulation is essential to advancing our understanding of this pathogen. The Agr1 system in has been thought to function by generating an extracellular autoinducing peptide that accumulates and exogenously activates two-component signaling. The absence of the peptide or protease should, in theory, result in similar phenotypes. However, in contrast to longstanding assumptions about Agr, we found that mutants of individual genes exhibit distinct phenotypes in These findings suggest that the Agr1 system may have other regulatory mechanisms independent of the typical Agr quorum sensing system. These data not only challenge models for Agr's mechanism of action in but also may expand our conceptions of how this system works in other Gram-positive pathogens.
辅助基因调控 1() 基因座由两个基因和组成,推测它们构成了一个自动诱导肽 (AIP) 系统。通常,AIP 系统通过 AgrB 介导的 AgrD 加工起作用,生成 AIP 的处理形式,提供浓度依赖性的细胞外信号。在这里,我们表明 630 Agr1 系统具有多种功能,并非所有功能都依赖于 AgrB1。CRISPR-Cas9n 缺失、或整个基因座导致孢子形成相关因子的转录发生变化,并且整体丧失了孢子形成。通过提供亲本菌株静止期培养物的上清液,突变体中的孢子形成得到恢复。相比之下,只有当 AgrB1 和 AgrD1 都被破坏时,运动性才会降低。最后,在没有 AgrB1 的情况下,AgrD1 肽在细胞质内积累,这与表达的增加相关(15 倍),以及编码两种主要毒素的和(20 倍)和(5 倍)。/或缺失的联合缺失并没有显著改变或的表达,但确实显示出对表达的轻微影响。总体而言,这些数据表明,630 中的 Agr1 系统执行多种功能,其中一些与典型的 AIP 信号有关,而另一些则涉及以前未知的作用机制。是一种产孢、产毒、厌氧细菌,可引起严重的胃肠道疾病。了解 感知生长条件以调节毒素表达和孢子形成的方式对于深入了解这种病原体至关重要。一直以来,人们认为中的 Agr1 系统通过生成一种积累并体外激活双组分信号的细胞外自动诱导肽来发挥作用。肽或蛋白酶的缺失按理应该导致类似的表型。然而,与长期以来关于 Agr 的假设相反,我们发现单个基因的突变体在中表现出不同的表型。这些发现表明,Agr1 系统可能具有独立于典型 Agr 群体感应系统的其他调节机制。这些数据不仅挑战了 Agr 在中的作用机制模型,而且可能扩展了我们对该系统在其他革兰氏阳性病原体中工作方式的概念。