Distinct Expression of the Two NO-Forming Nitrite Reductases in Thermus antranikianii DSM 12462 T Improved Environmental
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ENVIRONMENTAL MICROBIOLOGY
Distinct Expression of the Two NO-Forming Nitrite Reductases in Thermus antranikianii DSM 12462T Improved Environmental Adaptability Rui-Rui Liu 1 & Ye Tian 1 & En-Min Zhou 2 & Meng-Jie Xiong 1 & Min Xiao 1 & Wen-Jun Li 1,3 Received: 14 November 2019 / Accepted: 14 May 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Hot spring ecosystems are analogous to some thermal environments on the early Earth and represent ideal models to understand life forms and element cycling on the early Earth. Denitrification, an important component of biogeochemical nitrogen cycle, is highly active in hot springs. Nitrite (NO2−) reduction to nitric oxide (NO) is the significant and rate-limiting pathway in denitrification and is catalyzed by two types of nitrite reductases, encoded by nirS and nirK genes. NirS and NirK were originally considered incompatible in most denitrifying organisms, although a few strains have been reported to possess both genes. Herein, we report the functional division of nirS and nirK in Thermus, a thermophilic genus widespread in thermal ecosystems. Transcriptional levels of nirS and nirK coexisting in Thermus antranikianii DSM 12462T were measured to assess the effects of nitrite, oxygen, and stimulation time. Thirty-nine Thermus strains were used to analyze the phylogeny and distribution of nirS and nirK; six representative strains were used to assess the denitrification phenotype. The results showed that both genes were actively transcribed and expressed independently in T. antranikianii DSM 12462T. Strains with both nirS and nirK had a wider range of nitrite adaptation and revealed nir-related physiological adaptations in Thermus: nirK facilitated adaptation to rapid changes and extended the adaptation range of nitrite under oxygen-limited conditions, while nirS expression was higher under oxic and relatively stable conditions. Keywords Denitrification . Hot spring . nirS . nirK
Introduction Rui-Rui Liu and Ye Tian contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00248-020-01528-3) contains supplementary material, which is available to authorized users. * Wen-Jun Li [email protected] 1
State Key Laboratory of Biocontrol, Guangdong Provincial Key Laboratory of Plant Resources and Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), School of Life Sciences, Sun Yat-Sen University, Guangzhou 510275, People’s Republic of China
2
School of Resource Environment and Earth Science, Yunnan Institute of Geography, Yunnan University, Kunming 650091, People’s Republic of China
3
State Key Laboratory of Desert and Oasis Ecology, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, People’s Republic of China
Denitrification is a crucial part of the nitrogen cycle, in which nitrate nitrogen is transformed to gaseous forms, which prevents dynamically balanced ecosystems from undergoing eutrophication [[1, 2].
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