摘要
深地(地下深部)微生物是指陆地以及海底表面以下、不以光合作用为主要能量来源、生活在黑暗世界的微生物.深地微生物生活在岩石与沉积物空隙或者流体中,从岩石摄取营养,从水-岩反应中获取能量.深地微生物的总量可与地表生物量相媲美,但是其分布不均匀,代谢速率极低,地质条件是影响其分布和代谢的主要因素.总体来讲,随着深度的增加,由地表带入的有机质含量与能量都降低,因此微生物的丰度、多样性与活性也随之降低.在深部环境,深地微生物的代谢主要由水-岩反应产生的底物与能量维持.深地的极端环境造就了特殊的深地微生物(厌氧、化能自养、嗜热、嗜压、耐寡营养、耐辐射、耐干旱等),但是这些生物的生存边界目前还没有统一定论.尽管深地微生物个体小、生长慢,但是数量庞大,物种多样且功能丰富,在一系列地质过程中起着至关重要的作用,也与人类活动息息相关.因为获取深地样品难度大、费用高,因此深地微生物的研究尚不够深入,许多问题有待解决,包括深地微生物的起源、生存、与代谢功能,生物地理分布,由深地微生物参与调控的元素地球化学循环,以及深地微生物资源的开发利用.
The deep biosphere consists of microorganisms that thrive in continental and oceanic subsurface, and are independent of photosynthesis. Subsurface microorganisms live in rock fractures and subsurface fluids, and extract nutrients and energy from water-rock reactions. Globally, subsurface microbial biomass is comparable to total surface biomass, but its distribution is extremely heterogeneous, and metabolic rate is very slow, depending on specific geological conditions. Overall, with increased depth, microbial biomass, diversity, and activity decrease, likely because of more extreme environmental conditions in the subsurface(increased temperature and pressure, but decreased nutrients and pore space). Surface and shallow subsurface processes are driven by photosynthesis, and surface-derived H2O, O2, 14C, and 37Cl diffuse downward. Deep subsurface processes are driven by "geogas"(H2, CH4, CO2, and He). Temperature is the most important environmental condition that ultimately limits the depth of the biosphere, but this limit can be influenced by other conditions, such as nutrient levels and pressure. Limited data have shown that deep subsurface environment is dominated by bacteria( >50%) but archaea, eukaryotes and viruses are all present. Proteobacteria and Firmicutes are two dominant bacterial phyla and their relative proportions change with depth. In shallow and young sediments/rocks with relatively low temperature, Proteobacteria are dominant, but in deeper and older rocks with higher temperatures, Firmicutes become more important. Archaea are also widespread in the subsurface, and often consist of Euryarchaeota(dominantly Methanomicrobia) and Thaumarchaeota. Unlike sediments and sedimentary rocks at shallow depths where surface-derived organic matter is present, microbes in the deep subsurface usually depend on H2 as a major source of energy. H2 can be derived from several pathways including radiolysis of water, serpentinization of ultramafic and mafic rocks, and water splitting by highly oxidizing radicals. In
作者
董海良
Hailiang Dong(State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences,Beijing 100083,China)
出处
《科学通报》
EI
CAS
CSCD
北大核心
2018年第36期3885-3901,共17页
Chinese Science Bulletin
基金
国家自然科学基金(41572328
41630103)资助
关键词
深地微生物
极端环境
生存边界
能量
生物量
多样性
deep subsurface microbes
extreme environments
surviving boundary conditions
energy
biomass
diversity
