Shewanella species are widely distributed in marine environments, from the shallow coasts to the deepest sea bottom. Most Shewanella species possess two isoforms of periplasmic nitrate reductases (NAP-α and NAP-β) and are able to generate energy through nitrate reduction. However, the contributions of the two NAP systems to bacterial deep-sea adaptation remain unclear. In this study, we found that the deep-sea denitrifier Shewanella piezotolerans WP3 was capable of performing nitrate respiration under high hydrostatic pressure (HHP) conditions. In the wild-type strain, NAP-β played a dominant role and was induced by both the substrate and an elevated pressure, whereas NAP-α was constitutively expressed at a relatively lower level. Genetic studies showed that each NAP system alone was sufficient to fully sustain nitrate-dependent growth and that both NAP systems exhibited substrate and pressure inducible expression patterns when the other set was absent. Biochemical assays further demonstrated that NAP-α had a higher tolerance to elevated pressure. Collectively, we report for the first time the distinct properties and contributions of the two NAP systems to nitrate reduction under different pressure conditions. The results will shed light on the mechanisms of bacterial HHP adaptation and nitrogen cycling in the deep-sea environment.

中文翻译：

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压力调节基因表达和酶活性的深海细菌希瓦氏菌压电细菌WP3中的两个周质硝酸还原酶。

希瓦氏菌物种广泛分布在海洋环境中，从浅海沿岸到最深的海底。大多数希瓦氏菌属具有两种亚型的周质硝酸还原酶（NAP-α和NAP-β），并能够通过硝酸盐还原产生能量。但是，两个NAP系统对细菌深海适应的贡献尚不清楚。在这项研究中，我们发现深海反硝化装置Shewanella piezotolerans WP3能够在高静水压（HHP）条件下进行硝酸盐呼吸。在野生型菌株中，NAP-β起主要作用，并被底物和升高的压力诱导，而NAP-α则以相对较低的水平组成性表达。遗传研究表明，单独使用每个NAP系统足以完全维持硝酸盐依赖的生长，并且当缺少另一组时，两个NAP系统都显示底物和压力诱导型表达模式。生化分析进一步证明NAP-α对高压具有较高的耐受性。总的来说，我们首次报告了两种NAP系统在不同压力条件下对硝酸盐还原的独特性能和贡献。该结果将阐明深海环境中细菌HHP适应和氮循环的机制。我们首次报告了两种NAP系统在不同压力条件下对硝酸盐还原的独特性质和贡献。该结果将阐明深海环境中细菌HHP适应和氮循环的机制。我们首次报告了两种NAP系统在不同压力条件下对硝酸盐还原的独特性质和贡献。该结果将阐明深海环境中细菌HHP适应和氮循环的机制。