Alternative Oxidase Activity Reduces Stress in Vibrio fischeri Cells Exposed to Nitric Oxide
Alternative Oxidase Activity Reduces Stress in Vibrio fischeri Cells Exposed to Nitric Oxide
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替代氧化酶活性可减少暴露于一氧化氮的费氏弧菌细胞的压力
DOI：
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发表时间：
2018
影响因子：
3.2
通讯作者：
Anne K. Dunn
中科院分区：
文献类型：
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作者：
Anne K. Dunn
与典型的呼吸氧化酶不同，替代氧化酶（Aox）并不直接参与能量节约，其活性可能会降低呼吸效率和相关ATP的产生。已经在某些细菌中发现了Aox，其中大多数与海洋有关。这些细菌中Aox的存在提出了一个有趣的问题，即Aox的功能如何有利于细菌在海洋中的生长和生存。利用遗传上易于处理的海洋细菌费氏弧菌，我已经确定了Aox在通过有氧呼吸途径的电子通量被抑制的条件下减轻压力的作用。这些结果表明，在逆境条件下，Aox活性可能对细菌的长期适应性和生存产生积极影响。替代氧化酶（Aox）是一种在某些真核生物和细菌中发现的非节能呼吸氧化酶，其在生理学中的作用尚不完全清楚。利用遗传易感的细菌费氏弧菌作为模式生物，我已经确定了Aox在减少暴露于氧气和一氧化氮（NO）的细胞中的应激水平方面的作用。在缺乏NO解毒酶黄血红蛋白（Hmp）的费氏弧菌中，在氧气和NO存在下生长的细胞中，aox的缺失会导致转录组的改变，包括指向应激相关基因的转录本的增加。使用基于荧光的报告，我发现在缺乏aox的细胞中，细胞内活性氧种类相应增加，膜完整性降低。在这些生长条件下，Aox的活性与NADH水平的降低有关，表明Aox活性与NADH脱氢酶活性耦合。综上所述，这些结果表明，Aox的功能可以间接限制亚铁和有害羟基自由基的产生，有效地减少NO暴露时的细胞应激。与典型的呼吸氧化酶不同，替代氧化酶（Aox）并不直接参与能量节约，其活性可能会降低呼吸效率和相关ATP的产生。已经在某些细菌中发现了Aox，其中大多数与海洋有关。这些细菌中Aox的存在提出了一个有趣的问题，即Aox的功能如何有利于细菌在海洋中的生长和生存。利用遗传上易于处理的海洋细菌费氏弧菌，我已经确定了Aox在通过有氧呼吸途径的电子通量被抑制的条件下减轻压力的作用。这些结果表明，在逆境条件下，Aox活性可能对细菌的长期适应性和生存产生积极影响。
Unlike typical respiratory oxidases, alternative oxidase (Aox) does not directly contribute to energy conservation, and its activity would presumably reduce the efficiency of respiration and associated ATP production. Aox has been identified in certain bacteria, a majority of which are marine associated. The presence of Aox in these bacteria poses the interesting question of how Aox function benefits bacterial growth and survival in the ocean. Using the genetically tractable marine bacterium Vibrio fischeri, I have identified a role for Aox in reduction of stress under conditions where electron flux through the aerobic respiratory pathway is inhibited. These results suggest that Aox activity could positively impact longer-term bacterial fitness and survival under stressful environmental conditions. ABSTRACT Alternative oxidase (Aox) is a non-energy-conserving respiratory oxidase found in certain eukaryotes and bacteria, whose role in physiology is not entirely clear. Using the genetically tractable bacterium Vibrio fischeri as a model organism, I have identified a role for Aox to reduce levels of stress in cells exposed to oxygen and nitric oxide (NO). In V. fischeri lacking the NO-detoxifying enzyme flavohemoglobin (Hmp), deletion of aox in cells grown in the presence of oxygen and NO results in alterations to the transcriptome that include increases in transcripts mapping to stress-related genes. Using fluorescence-based reporters, I identified corresponding increases in intracellular reactive oxygen species and decreases in membrane integrity in cells lacking aox. Under these growth conditions, activity of Aox is linked to a decrease in NADH levels, indicating coupling of Aox activity with NADH dehydrogenase activity. Taken together, these results suggest that Aox functions to indirectly limit production of ferrous iron and damaging hydroxyl radicals, effectively reducing cellular stress during NO exposure. IMPORTANCE Unlike typical respiratory oxidases, alternative oxidase (Aox) does not directly contribute to energy conservation, and its activity would presumably reduce the efficiency of respiration and associated ATP production. Aox has been identified in certain bacteria, a majority of which are marine associated. The presence of Aox in these bacteria poses the interesting question of how Aox function benefits bacterial growth and survival in the ocean. Using the genetically tractable marine bacterium Vibrio fischeri, I have identified a role for Aox in reduction of stress under conditions where electron flux through the aerobic respiratory pathway is inhibited. These results suggest that Aox activity could positively impact longer-term bacterial fitness and survival under stressful environmental conditions.