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Methane-Eating Microbes of Tibetan-Plateau Meadows
Zheng, Y., Yang, W., Sun, X., Wang, S.-P., Rui, Y.-C., Luo, C.-Y. and Guo, L.-D. 2012. Methanotrophic community structure and activity under warming and grazing of alpine meadow on the Tibetan Plateau. Applied Microbiology and Biotechnology 93: 2193-2203.

The authors write that "methane (CH4) is the second most important greenhouse gas contributing roughly 20% to observed global warming (IPCC, 2007)," while adding that "oxidation of CH4 in soil by methane-oxidizing bacteria (methanotrophs) currently removes 30 Tg annually from the atmosphere, which equals 5.4% of the global CH4 sink (IPCC, 2007)." Thus, they but state the obvious when they further say that CH4-eating bacteria "play a critical role in the mitigation of global warming."

What was done
Working at the Haibei Alpine Meadow Ecosystem Research Station of the Chinese Academy of Sciences in Qinghai Province in the northeastern corner of the Tibetan Plateau, and utilizing the infrared heating system and free-air temperature enhancement protocol developed by Kimball et al. (2008), Zheng et al. studied the effects of a 1.2°C higher daylight temperature together with a 1.7°C higher nighttime temperature, with and without continuous concomitant grazing by adult Tibetan sheep, on methanotrophic abundance, community composition, and activity.

What was learned
As indicated in the figure below, in the non-grazed treatments, the experimental warming employed by the seven scientists increased methanotrophic abundance by approximately 93%, while in the grazed treatments, warming boosted methanotrophic abundance by more than twice that amount (183%).

Methanotrophic abundance, expressed as the number of pmoA gene copies of methanotrophs in the soils of the four different treatments (NWNG no warming with no grazing, NWG no warming with grazing, WNG warming with no grazing, WG warming with grazing). Adapted from Zheng et al. (2012).

What it means
Zheng et al. conclude that their findings imply that the Tibetan Plateau "may remove more CH4 [from the atmosphere] under future climate conditions." And, by inference, it can be concluded that such will likely be the case almost everywhere, for they write that "methanotrophs are widely distributed in various environments (e.g., McDonald et al., 2008; Op den Camp et al., 2009; Semrau et al., 2010), such as in paddy soils (Bodelier et al., 2000; Zheng et al., 2008), forest soils (Mohanty et al., 2007; Kolb, 2009), landfill soils (Chen et al., 2007; Einola et al., 2007; Semrau, 2011), grassland soils (Zhou et al., 2008; Abell et al., 2009), oil field soil (Zhang et al., 2010), and extreme thermoacidophilic environments (Dunfield et al., 2007; Pol et al., 2007; Islam et al., 2008)." Thus, it can be appreciated that this particular terrestrial impact of global warming constitutes a significant biologically-induced negative feedback.

Abell, G.C.J., Stralis-Pavese, N., Sessitsch, A. and Bodrossy, L. 2009. Grazing affects methanotroph activity and diversity in an alpine meadow soil. Environmental Microbiology Reports 1: 457-465.

Bodelier, P.L.E., Roslev, P., Henckel, T. and Frenzel, P. 2000. Stimulation by ammonium-based fertilizers of methane oxidation in soil around rice roots. Nature 403: 421-424.

Chen, Y., Dumont, M.G., Cebron, A. and Murrell, J.C. 2007. Identification of active methanotrophs in a landfill cover soil through detection of expression of 16S rRNA and functional genes. Environmental Microbiology 9: 2855-2869.

Dunfield, P.F., Yuryev, A., Senin, P., Smirnova, A.V., Stott, M.B., Hou, S.B., Ly, B., Saw, J.H., Zhou, Z.M., Ren, Y., Wang, J.M., Mountain, B..W., Crowe, M.A., Weatherby, T.M., Bodelier, P.L.E., Liesack, W., Feng, L., Wang, L. and Alam, M. 2007. Methane oxidation by an extremely acidophilic bacterium of the phylum Verrucomicrobia. Nature 450: 879-882.

Einola, J.K.M., Kettunen, R.H. and Rintala, J.A. 2007. Responses of methane oxidation to temperature and water content in cover soil of a boreal landfill. Soil Biology and Biochemistry 39: 1156-1164.

IPCC. 2007. Climate Change 2007: The Physical Science Basis. Solomon, S., Qin, D., Manniing, M., Chen, Z., Marquis, M., Averyt, K.B., Tignor, M. and Miller, H.L. (Eds.), Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom, pp. 539-543.

Islam, T., Jensen, S., Reigstad, L.J., Larsen, O., Birkeland, N.K. 2008. Methane oxidation at 55C and pH 2 by a thermoacidophilic bacterium belonging to the Verrucomicrobia phylum. Proceedings of the National Academy of Sciences, USA 105: 300-304.

Kimball, B.A., Conley, M.M., Wang, S.P., Lin, X.W., Luo, C.Y., Morgan, J. and Smith, D. 2008. Infrared heater arrays for warming ecosystem field plots. Global Change Biology 14: 309-320.

Kolb, S. 2009. The quest for atmospheric methane oxidizers in forest soils. Environmental Microbiology Reports 1: 336-346.

McDonald, I.R., Bodrossy, L., Chen, Y. and Murrell, J.C. 2008. Molecular ecology techniques for the study of aerobic methanotrophs. Applied Environmental Microbiology 74: 1305-1315.

Mohanty, S.R., Bodelier, P.L.E. and Conrad, R. 2007. Effect of temperature on composition of the methanotrophic community in rice field and forest soil. FEMS Microbiology Ecology 62: 24-31.

Op den Camp, H.J.M., Islam, T., Stott, M.B., Harhangi, H.R., Hynes, A., Schouten, S., Jetten, M.S.M., Birkeland, N.K., Pol, A. and Dunfield, P.F. 2009. Environmental, genomic and taxonomic perspectives on methanotrophic Verrucomicrobia. Environmental Microbiology Reports 1: 293-306.

Pol, A., Heijmans, K., Harhangi, H.R., Tedesco, D., Jetten, M.S.M. and Op den Camp, H.J.M. 2007. Methanotrophy below pH 1 by a new Verrucomicrobia species. Nature 450: 874-878.

Semrau, J.D. 2011. Current knowledge of microbial community structures in landfills and its cover soils. Applied Microbiology and Biotechnology 89: 961-969.

Semrau, J.D., DiSpirito, A.A. and Yoon, S. 2010. Methanotrophs and copper. FEMS Microbiology Reviews 34: 496-531.

Zhang, F., She, Y.H., Zheng, Y., Zhou, Z.F., Kong, S.Q. and Hou, D.J. 2010. Molecular biologic techniques applied to the microbial prospecting of oil and gas in the Ban 876 gas and oil field in China. Applied Microbiology and Biotechnology 86: 1183-1194.

Zheng, Y., Zhang, L.M., Zheng, Y.M., Di, H.J. and He, J.Z. 2008. Abundance and community composition of methanotrophs in a Chinese paddy soil under long-term fertilization practices. Journal of Soils and Sediments 8: 406-414.

Zhou, X.Q., Wang, Y.F., Huang, X.Z., Tian, J.Q. and Hao, Y.B. 2008. Effect of grazing intensities on the activity and community structure of methane-oxidizing bacteria of grassland soil in Inner Mongolia. Nutrient Cycling in Agroecosystems 80: 145-152.

Reviewed 25 July 2012