H₂O₂ concentration-dependent kinetics of gene expression: linking the intensity of oxidative stress and mycobacterial physiological adaptation

Defence against oxidative stress is crucial for <i>Mycobacterium tuberculosis</i> to survive and replicate within macrophages. Mycobacteria have evolved multilayer antioxidant systems, including scavenging enzymes, iron homeostasis, repair pathways, and metabolic adaptation, for coping with oxidative stress. How these systems are coordinated to enable the physiological adaptation to different intensities of oxidative stress, however, remains unclear. To address this, we investigated the expression kinetics of the well-characterized antioxidant genes at bacteriostatic H₂O₂ concentrations ranging from 1 mM to 10 mM employing <i>Mycolicibacterium smegmatis</i> as a model. Our results showed that most of the selected genes were expressed in a H₂O₂ concentration-dependent manner, whereas a subset exhibited sustained induction or repression without dose–effect, reflecting H₂O₂ concentration-dependent physiological adaptations. Through analyzing the dynamics of the coordinated gene expression, we demonstrated that the expressions of the H₂O₂ scavenging enzymes, DNA damage response, and Fe–S cluster repair function were strikingly correlated to the intensity of oxidative stress. The sustained induction of <i>mbtB</i>, <i>irtA</i>, and <i>dnaE2</i> indicated that mycobacteria might deploy increased iron acquisition and error-prone lesion bypass function as fundamental strategies to counteract oxidative damages, which are distinct from the defence tactics of <i>Escherichia coli</i> characterized by shrinking the iron pool and delaying the DNA repair. Moreover, the distinct gene expression kinetics among the tricarboxylic acid cycle, glyoxylate shunt, and methylcitrate cycle suggested that mycobacteria could dynamically redirect its metabolic fluxes according to the intensity of oxidative stress. This work defines the H₂O₂ concentration-dependent gene expression kinetics and provides unique insights into mycobacterial antioxidant defence strategies.

抗氧化应激防御对于结核分枝杆菌（Mycobacterium tuberculosis）在巨噬细胞内的存活与复制至关重要。分枝杆菌已演化出多层抗氧化系统，包括抗氧化清除酶、铁稳态、修复通路以及代谢适应机制，以应对氧化应激。然而，这些系统如何协同以实现对不同强度氧化应激的生理适应，目前仍不明确。为解决这一科学问题，本研究以耻垢分枝杆菌（Mycolicibacterium smegmatis）为模型，在1 mM至10 mM的抑菌性过氧化氢（H₂O₂）浓度条件下，探究了已得到充分表征的抗氧化基因的表达动力学。研究结果显示，多数所选基因的表达呈过氧化氢浓度依赖性模式，而部分基因则表现出持续的诱导或抑制且无剂量效应，这反映了机体针对过氧化氢浓度的生理性适应。通过分析协同基因表达的动态变化，本研究证实过氧化氢清除酶、DNA损伤应答以及铁硫簇修复功能的表达，与氧化应激强度显著相关。mbtB、irtA与dnaE2的持续诱导表明，分枝杆菌可能通过增强铁摄取与易错损伤旁路功能作为对抗氧化损伤的基础策略，这与大肠杆菌（Escherichia coli）通过缩减铁池与延缓DNA修复的防御策略截然不同。此外，三羧酸循环、乙醛酸分流与甲基柠檬酸循环间迥异的基因表达动力学表明，分枝杆菌可根据氧化应激强度动态重定向其代谢流。本研究明确了过氧化氢浓度依赖性的基因表达动力学，并为分枝杆菌的抗氧化防御策略提供了独特见解。

搜集汇总

背景与挑战

背景概述

该数据集研究了不同浓度过氧化氢（H2O2）下Mycolicibacterium smegmatis中抗氧化基因的表达动力学，揭示了氧化应激强度与分枝杆菌生理适应之间的关联。研究发现基因表达呈浓度依赖性，并涉及铁获取、DNA损伤修复和代谢重定向等防御策略，为理解分枝杆菌抗氧化机制提供了独特见解。