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Applied and Environmental Microbiology, November 2009, p. 6679-6687, Vol. 75, No. 21
0099-2240/09/$08.00+0     doi:10.1128/AEM.01021-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Correlation of Methane Production and Functional Gene Transcriptional Activity in a Peat Soil {triangledown}

Thomas E. Freitag and James I. Prosser*

Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen AB24 3UU, United Kingdom

Received 5 May 2009/ Accepted 3 September 2009

The transcription dynamics of subunit A of the key gene in methanogenesis (methyl coenzyme M reductase; mcrA) was studied to evaluate the relationship between process rate (methanogenesis) and gene transcription dynamics in a peat soil ecosystem. Soil methanogen process rates were determined during incubation of peat slurries at temperatures from 4 to 37°C, and real-time quantitative PCR was applied to quantify the abundances of mcrA genes and transcripts; corresponding transcriptional dynamics were calculated from mcrA transcript/gene ratios. Internal standards suggested unbiased recovery of mRNA abundances in comparison to DNA levels. In comparison to those in pure-culture studies, mcrA transcript/gene ratios indicated underestimation by 1 order of magnitude, possibly due to high proportions of inactive or dead methanogens. Methane production rates were temperature dependent, with maxima at 25°C, but changes in abundance and transcription of the mcrA gene showed no correlation with temperature. However, mcrA transcript/gene ratios correlated weakly (regression coefficient = 0.76) with rates of methanogenesis. Methanogen process rates increased over 3 orders of magnitude, while the corresponding maximum transcript/gene ratio increase was only 18-fold. mcrA transcript dynamics suggested steady-state expression in peat soil after incubation for 24 and 48 h, similar to that in stationary-phase cultures. mcrA transcript/gene ratios are therefore potential in situ indicators of methanogen process rate changes in complex soil systems.

* Corresponding author. Mailing address: Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen, Scotland AB24 3UU, United Kingdom. Phone: 44 (0)1224 273254. Fax: 44 (0)1224 272703. E-mail: j.prosser{at}abdn.ac.uk

{triangledown} Published ahead of print on 11 September 2009.

Applied and Environmental Microbiology, November 2009, p. 6679-6687, Vol. 75, No. 21
0099-2240/09/$08.00+0     doi:10.1128/AEM.01021-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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