Benda Martin, Schulz Lisa Maria, Stülke Jörg, Rismondo Jeanine
Department of General Microbiology, Institute of Microbiology and Genetics, Georg-August University Göttingen, Göttingen, Germany.
Front Microbiol. 2021 Apr 8;12:587035. doi: 10.3389/fmicb.2021.587035. eCollection 2021.
develops genetic competence for the uptake of foreign DNA when cells enter stationary phase and a high cell density is reached. These signals are integrated by the competence transcription factor ComK, which is subject to transcriptional, post-transcriptional and post-translational regulation. Many proteins are involved in the development of competence, both to control ComK activity and to mediate DNA uptake. However, for many proteins, the precise function they play in competence development is unknown. In this study, we assessed whether proteins required for genetic transformation play a role in the activation of ComK or rather act downstream of competence gene expression. While these possibilities could be distinguished for most of the tested factors, we assume that two proteins, PNPase and the transcription factor YtrA, are required both for full ComK activity and for the downstream processes of DNA uptake and integration. Further analyses of the role of the transcription factor YtrA for the competence development revealed that the overexpression of the YtrBCDEF ABC transporter in the mutant causes the loss of genetic competence. Moreover, overexpression of this ABC transporter also affects biofilm formation. Since the operon is naturally induced by cell wall-targeting antibiotics, we tested the cell wall properties upon overexpression of the ABC transporter and observed an increased thickness of the cell wall. The composition and properties of the cell wall are important for competence development and biofilm formation, suggesting that the observed phenotypes are the result of the increased cell wall thickness as an outcome of YtrBCDEF overexpression.
当细胞进入稳定期并达到高细胞密度时，会产生摄取外源DNA的遗传感受态。这些信号由感受态转录因子ComK整合，ComK受到转录、转录后和翻译后调控。许多蛋白质参与感受态的形成，既控制ComK的活性，又介导DNA摄取。然而，对于许多蛋白质来说，它们在感受态形成中所起的精确作用尚不清楚。在本研究中，我们评估了遗传转化所需的蛋白质是在ComK的激活中发挥作用，还是在感受态基因表达的下游起作用。虽然对于大多数测试因子来说可以区分这些可能性，但我们推测两种蛋白质，即多核苷酸磷酸化酶（PNPase）和转录因子YtrA，对于完整的ComK活性以及DNA摄取和整合的下游过程都是必需的。对转录因子YtrA在感受态形成中作用的进一步分析表明，在突变体中YtrBCDEF ABC转运蛋白的过表达导致遗传感受态丧失。此外，这种ABC转运蛋白的过表达也影响生物膜形成。由于该操纵子自然地由靶向细胞壁的抗生素诱导，我们在ABC转运蛋白过表达时测试了细胞壁特性，观察到细胞壁厚度增加。细胞壁的组成和特性对于感受态形成和生物膜形成很重要，这表明观察到的表型是YtrBCDEF过表达导致细胞壁厚度增加的结果。
