NC10 bacteria promoted methane oxidation coupled to chlorate reduction
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ORIGINAL PAPER
NC10 bacteria promoted methane oxidation coupled to chlorate reduction Zi-Yan Li . Xin Li . Bin Tan . Pan-Long Lv . He-Ping Zhao
Received: 31 July 2020 / Accepted: 5 September 2020 Ó Springer Nature B.V. 2020
Abstract The strictly anaerobic serum bottles were applied to investigate methane oxidation coupled to chlorate (ClO3-) reduction (MO-CR) without exogenous oxygen. 0.35 mM ClO3- was consumed within 20 days at the reduction rate of 17.50 lM/d, over three times than that of ClO4-. Chlorite (ClO2-) was not detected throughout the experiment and the mass recovery of Cl- was over 89%. Isotope tracing results showed most of 13CH4 was oxided to CO2, and the electrons recovery reached to 77.6%. Small amounts of 13CH4 was consumed for DOC production probably through aerobic methane oxidation process, with oxygen generated from disproportionation reaction. In pMMO (key enzyme in aerobic oxidation of
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10532-020-09912-z) contains supplementary material, which is available to authorized users. Z.-Y. Li P.-L. Lv H.-P. Zhao (&) Department of Environmental Engineering, College of Environmental and Resource Science, Zhejiang University, Hangzhou, China e-mail: [email protected] Z.-Y. Li P.-L. Lv H.-P. Zhao Key Lab Water Pollut Control & Environm Secur Tec, Zhejiang University, Hangzhou 310058, Zhejiang, China X. Li B. Tan Hangzhou Shangtuo Environmental Technology Co., Ltd, Hangzhou, China
methane) inhibition tests, ClO3- reduction rate was slowed to 7. 0 lmol/d by 2 mM C2H2, real-time quantitative PCR also showed the transcript abundance of pMMO and Cld were significantly dropped at the later period of experiment, indicating that the O2 disproportionated from ClO2- was utilized to active CH4. NC10 bacteria Candidatus Methylomirabilis, related closely to oxygenic denitrifiers M. oxyfera, was detected in the system, and got enriched along with chlorate reduction. Several pieces of evidence supported that NC10 bacteria promoted CH4 oxidation coupled to ClO3- reduction, these oxygenic denitrifiers may perform ClO2- disproportionation to produce O2, and then oxidized methane intracellularly. Keywords Chlorate reduction Methane oxidation NC10 Chlorite disproportionation
Introduction Denitrifying anaerobic methane oxidation (DAMO) is an important biochemical process in global nutrient cycles of carbon and nitrogen (Hinrichs et al. 1999; Raghoebarsing et al. 2006; Zhou et al. 2017). It is also regarded as an economical and environmental friendly wastewater treatment process, since microorganisms can use methane produced by anaerobic digestion to remove nitrogen in situ (Knittel and Boetius 2009).
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Biodegradation
DAMO process is performed through two different pathways: in ‘‘reverse methanogenesis’’ pathway, anaerobic methanotrophic archaea (ANME) utilizes CH4 to generate electrons via reverse methanogenesis, and then reduces nitrate (NO3-) to nitrite (NO
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