Unité Pathogenèse de Helicobacter, CNRS UMR 2001, Département de Microbiologie, Institut Pasteur, 75724 Paris Cedex 15, France.
Université de Paris, Sorbonne Paris Cité, 75013 Paris, France.
Proc Natl Acad Sci U S A. 2020 Dec 8;117(49):31398-31409. doi: 10.1073/pnas.2016195117. Epub 2020 Nov 23.
Toxin-antitoxin systems are found in many bacterial chromosomes and plasmids with roles ranging from plasmid stabilization to biofilm formation and persistence. In these systems, the expression/activity of the toxin is counteracted by an antitoxin, which, in type I systems, is an antisense RNA. While the regulatory mechanisms of these systems are mostly well defined, the toxins' biological activity and expression conditions are less understood. Here, these questions were investigated for a type I toxin-antitoxin system (AapA1-IsoA1) expressed from the chromosome of the human pathogen We show that expression of the AapA1 toxin in causes growth arrest associated with rapid morphological transformation from spiral-shaped bacteria to round coccoid cells. Coccoids are observed in patients and during in vitro growth as a response to different stress conditions. The AapA1 toxin, first molecular effector of coccoids to be identified, targets inner membrane without disrupting it, as visualized by cryoelectron microscopy. The peptidoglycan composition of coccoids is modified with respect to spiral bacteria. No major changes in membrane potential or adenosine 5'-triphosphate (ATP) concentration result from AapA1 expression, suggesting coccoid viability. Single-cell live microscopy tracking the shape conversion suggests a possible association of this process with cell elongation/division interference. Oxidative stress induces coccoid formation and is associated with repression of the antitoxin promoter and enhanced processing of its transcript, leading to an imbalance in favor of AapA1 toxin expression. Our data support the hypothesis of viable coccoids with characteristics of dormant bacteria that might be important in infections refractory to treatment.
毒素-抗毒素系统存在于许多细菌染色体和质粒中，其作用范围从质粒稳定到生物膜形成和持久性。在这些系统中，毒素的表达/活性受到抗毒素的拮抗，而在 I 型系统中，抗毒素是一种反义 RNA。虽然这些系统的调控机制大多已经明确，但毒素的生物学活性和表达条件了解较少。在这里，我们研究了人病原体 染色体上表达的 I 型毒素-抗毒素系统（AapA1-IsoA1）的这些问题。我们表明，AapA1 毒素在 中的表达会导致生长停滞，并伴有快速的形态转变，从螺旋形细菌转变为圆形球菌细胞。球菌在患者和体外生长中作为对不同应激条件的反应而被观察到。AapA1 毒素是鉴定出的第一个球菌的分子效应物，它靶向 内膜而不破坏它，这可以通过冷冻电子显微镜观察到。与螺旋细菌相比，球菌的肽聚糖组成发生了修饰。AapA1 表达不会导致膜电位或三磷酸腺苷 (ATP) 浓度的主要变化，这表明球菌具有活力。单细胞实时显微镜跟踪形态转换表明，这个过程可能与细胞伸长/分裂干扰有关。氧化应激诱导球菌形成，并与抗毒素启动子的抑制和其转录本的加工增强相关，导致有利于 AapA1 毒素表达的不平衡。我们的数据支持了具有休眠细菌特征的活球菌的假说，这在治疗抵抗的 感染中可能很重要。
