Thummes Kathrin, Kämpfer Peter, Jäckel Udo
Institut für Angewandte Mikrobiologie, Justus-Liebig-Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Syst Appl Microbiol. 2007 Jul;30(5):418-29. doi: 10.1016/j.syapm.2007.01.006. Epub 2007 Mar 2.
To date, composting has been regarded as an aerobic process but it has been shown that composting piles are often sources of atmospheric methane. In order to gain a more comprehensive view on the diversity of methanogenic Archaea in compost, gas chromatographical methods and molecular cloning were used to study relationships of thermophilic archaeal communities and changes in methane production potential during compost maturation. According to the thermophilic methane production potential, wide differences could be detected between differently aged compost materials. In material derived from 3- and 4-week-old piles, low and no thermophilic methane production potential, respectively, was observed at 50 degrees C. Material from a 6-week-old pile showed the maximum methane production. With compost maturation, the production slowly decreased again with 6 weeks, 8 weeks, and mature compost showing an optimum methane production potential at 60 degrees C. At 70 degrees C, only 6-week-old material showed a comparable high production of methane. The 16S rRNA-based phylogenetic surveys revealed an increase of archaeal diversity with compost maturation. In the 6-week-old material, 86% of the sequences in the archaeal 16S rRNA library had the highest sequence similarities to Methanothermobacter spp. and the remaining 14% of the clones were related to Methanosarcina thermophila. Quantification of methanogens in 6-week-old material, on the basis of the methane production rate, resulted in values of about 2x10(7) cells per gram fresh weight. In 8-week-old and mature compost material, the proportion of sequences similar to Methanothermobacter spp. decreased to 34% and 0%, respectively. The mature compost material showed the highest variation in identified sequences, although 33% could be assigned to as yet uncultured Archaea (e.g. Rice cluster I, III, and IV). Our results indicate that compost harbours a diverse community of thermophilic methanogens, with changing composition during the maturation process, presumably due to altered pile conditions. Likewise, compost may act as a potential carrier for thermophilic methanogens in temperate soils because it is widely used as a soil amendment.
迄今为止，堆肥一直被视为一个需氧过程，但已表明堆肥堆常常是大气甲烷的来源。为了更全面地了解堆肥中产甲烷古菌的多样性，采用气相色谱法和分子克隆技术研究了嗜热古菌群落的关系以及堆肥成熟过程中甲烷产生潜力的变化。根据嗜热甲烷产生潜力，可检测到不同陈化程度的堆肥材料之间存在很大差异。在源自3周龄和4周龄堆的材料中，在50摄氏度时分别观察到低嗜热甲烷产生潜力和无嗜热甲烷产生潜力。来自6周龄堆的材料显示出最大的甲烷产量。随着堆肥成熟，产量在6周、8周时又缓慢下降，成熟堆肥在60摄氏度时显示出最佳甲烷产生潜力。在70摄氏度时，只有6周龄的材料显示出相当高的甲烷产量。基于16S rRNA的系统发育调查显示，随着堆肥成熟，古菌多样性增加。在6周龄的材料中，古菌16S rRNA文库中86%的序列与嗜热栖热甲烷杆菌属（Methanothermobacter spp.）具有最高的序列相似性，其余14%的克隆与嗜热甲烷八叠球菌（Methanosarcina thermophila）相关。根据甲烷产生速率对6周龄材料中的产甲烷菌进行定量，结果约为每克鲜重2×10⁷个细胞。在8周龄和成熟堆肥材料中，与嗜热栖热甲烷杆菌属相似的序列比例分别降至34%和0%。成熟堆肥材料在已鉴定序列中显示出最高的变异性，尽管33%可归为尚未培养的古菌（如水稻菌群I、III和IV）。我们的结果表明，堆肥中含有多样的嗜热产甲烷菌群落，在成熟过程中其组成会发生变化，推测是由于堆肥条件改变所致。同样，堆肥可能作为温带土壤中嗜热产甲烷菌的潜在载体，因为它被广泛用作土壤改良剂。
