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Applied and Environmental Microbiology, October 2008, p. 6114-6120, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.01146-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Methanogenesis from Methanol at Low Temperatures by a Novel Psychrophilic Methanogen, "Methanolobus psychrophilus" sp. nov., Prevalent in Zoige Wetland of the Tibetan Plateau ^,

Guishan Zhang,^1,2 Na Jiang,² Xiaoli Liu,¹ and Xiuzhu Dong^1*

State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, People's Republic of China,¹ Graduate School, Chinese Academy of Sciences, Beijing 100049, People's Republic of China²

Received 21 May 2008/ Accepted 28 July 2008

The Zoige wetland of the Tibetan plateau is at permanent low temperatures and is a methane emission heartland of the plateau; however, cold-adaptive methanogens in the soil are poorly understood. In this study, a variety of methanogenic enrichments at 15°C and 30°C were obtained from the wetland soil. It was demonstrated that hydrogenotrophic methanogenesis was the most efficient type at 30°C, while methanol supported the highest methanogenesis rate at 15°C. Moreover, methanol was the only substrate to produce methane more efficiently at 15°C than at 30°C. A novel psychrophilic methanogen, strain R15, was isolated from the methanol enrichment at 15°C. Phylogenetic analysis placed strain R15 within the genus Methanolobus, loosely clustered with Methanolobus taylorii (96.7% 16S rRNA similarity). R15 produced methane from methanol, trimethylamine, and methyl sulfide and differed from other Methanolobus species by growing and producing methane optimally at 18°C (specific growth rate of 0.063 ± 0.001 h^–1) and even at 0°C. Based on these characteristics, R15 was proposed to be a new species and named "Methanolobus psychrophilus" sp. nov. The K_m and V_max of R15 for methanol conversion were determined to be 87.5 ± 0.4 µM and 0.39 ± 0.04 mM h^–1 at 18°C, respectively, indicating a high affinity and conversion efficiency for methanol. The proportion of R15 in the soil was determined by quantitative PCR, and it accounted for 17.2% ± 2.1% of the total archaea, enumerated as 10⁷ per gram of soil; the proportion was increased to 42.4% ± 2.3% in the methanol enrichment at 15°C. This study suggests that the psychrophilic methanogens in the Zoige wetland are likely to be methylotrophic and to play a role in methane emission of the wetland.

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* Corresponding author. Mailing address: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, No. 3A, Datun Road, Chaoyang District, Beijing 100101, People's Republic of China. Phone and fax: 86 10 6480 7413. E-mail: dongxz{at}sun.im.ac.cn

Published ahead of print on 1 August 2008.

Supplemental material for this article may be found at http://aem.asm.org/.

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Applied and Environmental Microbiology, October 2008, p. 6114-6120, Vol. 74, No. 19
0099-2240/08/$08.00+0     doi:10.1128/AEM.01146-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.