Liu Jia-Rong, Wang Zhi-Qing, Li Fei-Fei, Li Zhen-Kun, Wang Ming-Chen, Wang Na, An Yu, Chen Xiu-Lan, Zhang Yu-Zhong, Fu Hui-Hui
MOE Key Laboratory of Evolution and Marine Biodiversity, Frontiers Science Center for Deep Ocean Multispheres and Earth System & College of Marine Life Sciences, Ocean University of China, Qingdao, China.
Laboratory for Marine Biology and Biotechnology, Qingdao Marine Science and Technology Center, Qingdao, China.
Microbiol Spectr. 2025 Jul;13(7):e0332424. doi: 10.1128/spectrum.03324-24. Epub 2025 May 16.
NADH oxidation by NADH dehydrogenases (NDHs) is crucial for feeding respiratory quinone pool and maintaining the balance of NADH/NAD. In the respiratory model organism , which possesses four NDHs, the longstanding notion had been that NDHs were not required under anoxic conditions until recent studies demonstrated their role in extracellular electron transfer. However, the role of each NDH, particularly under anoxic conditions, has not been characterized. Here, we systematically investigated the role of each NDH in aerobic and anaerobic nitrate and nitrite respiration using NDH triple mutants. We corroborated the involvement of NDHs in anaerobic nitrate/nitrite respiration, revealing different repertoires of NDHs employed by in response to electron acceptor (EA) availability. The transcript levels of two were modulated by the EA conversion from nitrate to nitrite. Furthermore, we demonstrated that the global regulators Crp and the Arc system both directly controlled the transcription of four NDHs during nitrate/nitrite respiration. This study confirms the requirement of NDHs for anaerobic nitrate and nitrite respiration and sheds light on the respiratory remodeling mechanism whereby global regulators coordinate NDH genes transcription to adapt to redox-stratified environments.IMPORTANCENADH is an important electron source for the respiratory quinone pool. Multiple NADH dehydrogenases (NDHs) are widely present in prokaryotes, indicating the flexibility in NADH oxidation. As a renowned respiratory versatile model strain, possesses four NDHs, encompassing all three types of NDHs, with varying ion-translocating efficiencies. The redundancy of NDHs may confer advantages for to survive and thrive in redox-stratified environments. However, the roles of each NDH, especially in anaerobic respiration, are less understood. Here, we evaluated the role of each NDH in aerobic and anaerobic nitrate/nitrite respiration. We found that the conversion of electron acceptor from nitrate to nitrite triggered the changes in the transcriptional levels of NDH genes, and global regulators Crp and the Arc system were involved in these processes. These findings elucidate the mechanism of the respiratory chain remodeling at the NADH oxidation step in response to different electron acceptors.
NADH脱氢酶（NDHs）催化的NADH氧化对于为呼吸醌池供料以及维持NADH/NAD平衡至关重要。在拥有四种NDHs的呼吸模式生物中，长期以来的观点一直是在缺氧条件下不需要NDHs，直到最近的研究证明了它们在细胞外电子转移中的作用。然而，每种NDH的作用，特别是在缺氧条件下的作用，尚未得到明确。在这里，我们使用NDH三突变体系统地研究了每种NDH在好氧和厌氧硝酸盐及亚硝酸盐呼吸中的作用。我们证实了NDHs参与厌氧硝酸盐/亚硝酸盐呼吸，揭示了根据电子受体（EA）可用性而采用的不同NDH组合。两种NDHs的转录水平受EA从硝酸盐向亚硝酸盐转化的调节。此外，我们证明全局调节因子Crp和Arc系统在硝酸盐/亚硝酸盐呼吸过程中都直接控制四种NDHs的转录。本研究证实了NDHs在厌氧硝酸盐和亚硝酸盐呼吸中的必要性，并揭示了全局调节因子协调NDH基因转录以适应氧化还原分层环境的呼吸重塑机制。
重要性
NADH是呼吸醌池的重要电子来源。多种NADH脱氢酶（NDHs）广泛存在于原核生物中，表明NADH氧化具有灵活性。作为著名的呼吸通用模式菌株，拥有四种NDHs，涵盖所有三种类型的NDHs，具有不同的离子转运效率。NDHs的冗余可能赋予其在氧化还原分层环境中生存和繁衍的优势。然而，每种NDH的作用，尤其是在厌氧呼吸中的作用，了解较少。在这里，我们评估了每种NDH在好氧和厌氧硝酸盐/亚硝酸盐呼吸中的作用。我们发现电子受体从硝酸盐向亚硝酸盐的转化引发了NDH基因转录水平的变化，全局调节因子Crp和Arc系统参与了这些过程。这些发现阐明了呼吸链在NADH氧化步骤响应不同电子受体的重塑机制。
