Institute of Biological and Environmental Sciences, University of Aberdeen, Cruickshank Building, St. Machar Drive, Aberdeen, Scotland AB24 3UU, United Kingdom.
Appl Environ Microbiol. 2009 Nov;75(21):6679-87. doi: 10.1128/AEM.01021-09. Epub 2009 Sep 11.
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 degrees 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 degrees 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.
研究了产甲烷关键基因亚单位 A（甲基辅酶 M 还原酶；mcrA）的转录动态，以评估泥炭土壤生态系统中过程速率（产甲烷作用）与基因转录动态之间的关系。在 4 至 37 摄氏度的温度下培养泥炭泥浆时，确定了土壤产甲烷菌的过程速率，并应用实时定量 PCR 来定量 mcrA 基因和转录本的丰度；从 mcrA 转录本/基因比计算相应的转录动态。与 DNA 水平相比，内部标准表明 mRNA 丰度的无偏回收。与纯培养研究相比，mcrA 转录本/基因比表明低估了 1 个数量级，可能是由于高比例的非活性或死亡产甲烷菌所致。甲烷生成速率随温度而变化，在 25 摄氏度时达到最大值，但 mcrA 基因的丰度和转录变化与温度没有相关性。然而，mcrA 转录本/基因比与产甲烷作用的速率呈弱相关（回归系数=0.76）。产甲烷菌的过程速率增加了 3 个数量级，而相应的最大转录本/基因比增加仅为 18 倍。mcrA 转录本动力学表明在 24 和 48 小时孵育后，泥炭土壤中的表达处于稳定状态，类似于静止期培养物中的表达。因此，mcrA 转录本/基因比是复杂土壤系统中产甲烷菌过程速率变化的潜在原位指示物。
