基于甲酰四氢叶酸合成酶基因解析厌氧消化系统中互营乙酸氧化菌群

Analysis of Syntrophic Acetate-oxidizing Bacterial Community in Anaerobic Digesters Based on Formyltetrahydrofolate Synthetase Gene

乙酸是厌氧消化产甲烷过程的重要中间代谢产物,可以通过乙酸营养型产甲烷菌分解乙酸和互营乙酸氧化菌氧化乙酸这两种途径产甲烷。一些同型产乙酸菌通过逆向acetyl-CoA途径可以进行互营乙酸氧化,甲酰四氢叶酸合成酶(formyltetrahydrofolate synthetase,FTHFS)是该途径关键酶,其编码基因甲酰四氢叶酸合成酶基因(fhs)可以用来研究环境中互营乙酸氧化菌群分布,但目前相关研究比较有限。为了了解乙酸氧化菌群的多样性和分布情况,研究采集了分别来自供给原料不同、运行温度不同的湿式和干式的厌氧反应器的消化污泥,按样品的来源特征构建3个fhs基因克隆文库并进行了解析。结果表明:3个文库的克隆分布差异大且没有共有克隆,大部分克隆与已知微生物或未培养克隆具有较低的相似性,表明厌氧消化系统中存在较高多样性的未知互营乙酸氧化菌群,运行温度对互营乙酸氧化菌群多样性具有一定影响。

Acetate is a significant intermediate during anaerobic digestion of organic wastes. There are two pathways for converting acetate to CH4 ： acetoclastic methanogenesis by acetoclastic methanogens and syntrophic acetate oxidation by syntrophy of acetate-oxidizing bacteria and hydrogenotrophic methanogens. Some homoacetogenic bacteria may reverse the direction of the acetyl-CoA pathway for syntrophie acetate oxidation. Formyltetrahydrofolate synthetase （FTHFS） is one of the key enzymes in this pathway. The gene （fhs） coding formyltetrahydrofolate synthetase can be used for studying syntrophic acetate-oxidizing bacteria （SAOB）, but the research is limited to date. In this study, sludges from both mesophilic and thermophilic wet and dry anaerobic digesters treating different wastes were collected for the study of SAOB. Threefhs gene clone libraries were constructed. The result showed that the distribution of clones in the three clone libraries was very different and no same clones were found in all the three clone libraries ; most of clones had low sequencing similarity with known bacteria or uncultured clones. The results suggested that there was a large number of unknow SAOB with high diversity in anaerobic digesters and the operation temperature might be an important factor affecting the diversity of SAOB.