Oxidative stresses commonly exist in natural environments, and microbes have developed a variety of defensive systems to counteract such events. Although increasing evidence has shown that high hydrostatic pressure (HHP) and low temperature (LT) induce antioxidant defense responses in cells, there is no direct evidence to prove the connection between antioxidant defense mechanisms and the adaptation of bacteria to HHP and LT. In this study, using the wild-type (WT) strain of a deep-sea bacterium, Shewanella piezotolerans WP3, as an ancestor, we obtained a mutant, OE100, with an enhanced antioxidant defense capacity by experimental evolution under H2O2 stress. Notably, OE100 exhibited better tolerance not only to H2O2 stress but also to HHP and LT (20 MPa and 4°C, respectively). Whole-genome sequencing identified a deletion mutation in the oxyR gene, which encodes the transcription factor that controls the oxidative stress response. Comparative transcriptome analysis showed that the genes associated with oxidative stress defense, anaerobic respiration, DNA repair, and the synthesis of flagella and bacteriophage were differentially expressed in OE100 compared with the WT at 20 MPa and 4°C. Genetic analysis of oxyR and ccpA2 indicated that the OxyR-regulated cytochrome c peroxidase CcpA2 significantly contributed to the adaptation of WP3 to HHP and LT. Taken together, these results confirmed the inherent relationship between antioxidant defense mechanisms and the adaptation of a benthic microorganism to HHP and LT.IMPORTANCE Oxidative stress exists in various niches, including the deep-sea ecosystem, which is an extreme environment with conditions of HHP and predominantly LT. Although previous studies have shown that HHP and LT induce antioxidant defense responses in cells, direct evidence to prove the connection between antioxidant defense mechanisms and the adaptation of bacteria to HHP and LT is lacking. In this work, using the deep-sea bacterium Shewanella piezotolerans WP3 as a model, we proved that enhancement of the adaptability of WP3 to HHP and LT can benefit from its antioxidant defense mechanism, which provided useful insight into the ecological roles of antioxidant genes in a benthic microorganism and contributed to an improved understanding of microbial adaptation strategies in deep-sea environments.

中文翻译：

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通过H2O2胁迫下的实验进化，提高深海细菌希瓦氏菌希瓦氏菌WP3对高压和低温的适应性。

氧化应激通常存在于自然环境中，微生物已经开发出多种防御系统来抵抗此类事件。尽管越来越多的证据表明高静水压（HHP）和低温（LT）会诱导细胞中的抗氧化剂防御反应，但没有直接证据证明抗氧化剂防御机制与细菌对HHP和LT的适应之间存在联系。在这项研究中，使用深海细菌希瓦氏菌（Shewanella piezotolerans WP3）的野生型（WT）菌株作为祖先，我们通过在H2O2胁迫下的实验进化获得了具有增强的抗氧化防御能力的OE100突变体。值得注意的是，OE100不仅表现出对H2O2应力的耐受性，而且表现出对HHP和LT（分别为20 MPa和4°C）的耐受性。全基因组测序确定了oxyR基因的缺失突变，该基因编码控制氧化应激反应的转录因子。比较转录组分析显示，与WT在20 MPa和4°C下相比，与WT相比，与氧化应激防御，无氧呼吸，DNA修复以及鞭毛和噬菌体合成相关的基因差异表达。oxyR和ccpA2的遗传分析表明，OxyR调节的细胞色素c过氧化物酶CcpA2显着促进了WP3对HHP和LT的适应性。综上所述，这些结果证实了抗氧化防御机制与底栖微生物对HHP和LT的适应之间的内在联系。重要信息氧化应激存在于各个生态位中，包括深海生态系统，这是具有HHP和主要是LT条件的极端环境。尽管以前的研究表明HHP和LT会诱导细胞中的抗氧化剂防御反应，但缺乏直接的证据来证明抗氧化剂防御机制与细菌对HHP和LT的适应之间的联系。在这项工作中，使用深海细菌嗜热希瓦氏菌WP3作为模型，我们证明了WP3对HHP和LT的适应性增强可以受益于其抗氧化防御机制，这为了解抗氧化基因在大肠杆菌中的生态作用提供了有用的见识。底栖微生物，有助于更好地了解深海环境中的微生物适应策略。尽管以前的研究表明HHP和LT会诱导细胞中的抗氧化剂防御反应，但缺乏直接的证据来证明抗氧化剂防御机制与细菌对HHP和LT的适应之间的联系。在这项工作中，使用深海细菌嗜热希瓦氏菌WP3作为模型，我们证明了WP3对HHP和LT的适应性增强可以受益于其抗氧化防御机制，这为了解抗氧化基因在大肠杆菌中的生态作用提供了有用的见识。底栖微生物，有助于更好地了解深海环境中的微生物适应策略。尽管以前的研究表明HHP和LT会诱导细胞中的抗氧化剂防御反应，但缺乏直接的证据来证明抗氧化剂防御机制与细菌对HHP和LT的适应之间的联系。在这项工作中，使用深海细菌嗜热希瓦氏菌WP3作为模型，我们证明了WP3对HHP和LT的适应性增强可以受益于其抗氧化防御机制，这为了解抗氧化基因在大肠杆菌中的生态作用提供了有用的见识。底栖微生物，有助于更好地了解深海环境中的微生物适应策略。