Angel Roey, Conrad Ralf
Max-Planck-Institute for Terrestrial Microbiology, D-35043 Marburg, Germany.
Environ Microbiol. 2009 Oct;11(10):2598-610. doi: 10.1111/j.1462-2920.2009.01984.x. Epub 2009 Jul 6.
Aerated soils are a biological sink for atmospheric methane. However, the activity of desert soils and the presence of methanotrophs in these soils have hardly been studied. We studied on-site atmospheric methane consumption rates as well as the diversity and expression of the pmoA gene, coding for a subunit of the particulate methane monooxygenase, in arid and hyperarid soils in the Negev Desert, Israel. Methane uptake was only detected in undisturbed soils in the arid region (approximately 90 mm year(-1)) and vertical methane profiles in soil showed the active layer to be at 0-20 cm depth. No methane uptake was detected in the hyperarid soils (approximately 20 mm year(-1)) as well as in disturbed soils in the arid region (i.e. agricultural field and a mini-catchment). Molecular analysis of the methanotrophic community using terminal restriction fragment length polymorphism (T-RFLP) and cloning/sequencing of the pmoA gene detected methanotrophs in the active soils, whereas the inactive ones were dominated by sequences of the homologous gene amoA, coding for a subunit of the ammonia monooxygenase. Even in the active soils, methanotrophs (as well as in situ activity) could not be detected in the soil crust, which is the biologically most important layer in desert soils. All pmoA sequences belonged to yet uncultured strains. Transcript analysis showed dominance of sequences clustering within the JR3, formerly identified in Californian grassland soils. Our results show that although active methanotrophs are prevalent in arid soils they seem to be absent or inactive in hyperarid and disturbed arid soils. Furthermore, we postulate that methanotrophs of the yet uncultured JR3 cluster are the dominant atmospheric methane oxidizers in this ecosystem.
通气良好的土壤是大气甲烷的生物汇。然而，沙漠土壤的活性以及这些土壤中甲烷氧化菌的存在情况几乎未被研究过。我们研究了以色列内盖夫沙漠干旱和超干旱土壤中现场大气甲烷消耗速率以及编码颗粒甲烷单加氧酶一个亚基的pmoA基因的多样性和表达情况。仅在干旱地区未受干扰的土壤中检测到甲烷吸收（约90毫米/年），土壤中的垂直甲烷剖面显示活性层在0 - 20厘米深度。在超干旱土壤（约20毫米/年）以及干旱地区受干扰的土壤（即农田和小型集水区）中未检测到甲烷吸收。使用末端限制性片段长度多态性（T - RFLP）对甲烷营养群落进行分子分析以及对pmoA基因进行克隆/测序，在活性土壤中检测到了甲烷氧化菌，而无活性土壤则以编码氨单加氧酶一个亚基的同源基因amoA的序列为主。即使在活性土壤中，在土壤结皮中也未检测到甲烷氧化菌（以及原位活性），而土壤结皮是沙漠土壤中生物学上最重要的层。所有pmoA序列都属于尚未培养的菌株。转录本分析表明，聚类在JR3内的序列占主导地位，JR3此前在加利福尼亚草原土壤中被鉴定出来。我们的结果表明，尽管活性甲烷氧化菌在干旱土壤中普遍存在，但在超干旱和受干扰的干旱土壤中似乎不存在或无活性。此外，我们推测尚未培养的JR3聚类的甲烷氧化菌是该生态系统中主要的大气甲烷氧化菌。
