Gelwicks J T, Risatti J B, Hayes J M
Departments of Chemistry and Geological Sciences, Indiana University, Bloomington 47405, USA.
Appl Environ Microbiol. 1994 Feb;60(2):467-72. doi: 10.1128/aem.60.2.467-472.1994.
The carbon isotope effects associated with synthesis of methane from acetate have been determined for Methanosarcina barkeri 227 and for methanogenic archaea in sediments of Wintergreen Lake, Michigan. At 37 degrees C, the 13C isotope effect for the reaction acetate (methyl carbon) --> methane, as measured in replicate experiments with M. barkeri, was - 21.3% +/- 0.3%. The isotope effect at the carboxyl portion of acetate was essentially equal, indicating participation of both positions in the rate-determining step, as expected for reactions catalyzed by carbon monoxide dehydrogenase. A similar isotope effect, - 19.2% +/- 0.3% was found for this reaction in the natural community (temperature = 20 degrees C). Given these observations, it has been possible to model the flow of carbon to methane within lake sediment communities and to account for carbon isotope compositions of evolving methane. Extension of the model allows interpretation of seasonal fluctuations in 13C contents of methane in other systems.
已测定了巴氏甲烷八叠球菌227以及密歇根州温特格林湖沉积物中产甲烷古菌从乙酸盐合成甲烷过程中的碳同位素效应。在37摄氏度下，用巴氏甲烷八叠球菌进行重复实验测得，乙酸盐（甲基碳）→甲烷反应的13C同位素效应为-21.3%±0.3%。乙酸盐羧基部分的同位素效应基本相同，这表明两个位置都参与了速率决定步骤，这与一氧化碳脱氢酶催化的反应预期一致。在自然群落中（温度=20摄氏度），该反应也发现了类似的同位素效应，为-19.2%±0.3%。基于这些观察结果，现已能够对湖泊沉积物群落中碳向甲烷的流动进行建模，并解释不断生成的甲烷的碳同位素组成。该模型的扩展有助于解释其他系统中甲烷13C含量的季节性波动。
