我国典型森林土壤微生物驱动的氮代谢途径特征解析

微生物介导的氮代谢途径对生态系统结构和功能稳定性的维持起着重要作用，阐明微生物群落与氮代谢途径之间的关系可以从微观水平上扩展对氮代谢途径的理解.然而，微生物的基因水平转移使得基于分类学的方法并不能说明两者之间的关系.有研究表明，功能性状影响着群落构建和生态系统功能，将基于功能性状的研究方法应用于土壤微生物能更好地说明氮代谢途径的特征.因此，本文选择5种我国典型森林土壤，包括黑土（黑龙江哈尔滨）、暗棕壤（吉林长白山）、黄棕壤（湖北武汉）、红壤（福建福州）和砖红壤（海南乐东），利用可以量化微生物功能性状的宏基因组技术对不同森林土的氮代谢途径特征进行了研究，主要包括氨同化、硝酸盐异化还原、硝酸盐同化还原、反硝化、硝化、固氮和厌氧氨氧化过程.结果表明，细菌序列在宏基因组文库中占主导位置，占所有序列的98.02%，且所涉及的几种氮代谢途径在细菌中都被检测到.5种森林土有着相同的氮代谢途径特征，即氨同化是细菌中检出频率最高的氮代谢途径，每百万个带注释的细菌序列平均检测到2830个氨同化途径的功能基因，固氮和厌氧氨氧化代谢途径检出频率较低，每百万个序列分别只检测到28.3和10.7个功能基因.不同森林土壤中同一氮代谢过程可由不同的微生物参与，且负责整个氮代谢途径的微生物的群落结构不完全相同.

Analysis of the Traits of Nitrogen Metabolism Pathways for Several Forest Soils in Eastern China

Nitrogen metabolism pathways mediated by microorganisms play an important role in maintaining the structure and functional stability of soil ecosystems. Clarifying the relationships between microbial communities and nitrogen metabolism pathways can expand our understanding of nitrogen metabolism pathways at a microscopic level. However, the horizontal gene transfer of microorganisms means that taxonomy-based methods cannot be easily applied. A growing number of studies have shown that functional traits affect community construction and ecosystem functions. Using methods based on functional traits to study soil microbial communities can, therefore, better characterize nitrogen metabolism pathways. Here, five typical forest soils in China, namely black soil(Harbin, Heilongjiang), dark-brown earth(Changbaishan, Jilin), yellow-brown earth(Wuhan, Hubei), red earth(Fuzhou, Fujian), and humid-thermo ferralitic soil(Ledong, Hainan), were selected to study the traits of nitrogen metabolism pathways using metagenomic technology combined with the trait-based methods. The studied nitrogen metabolism pathways were ammonia assimilation, nitrate dissimilatory reduction, nitrate assimilatory reduction, denitrification, nitrification, nitrogen fixation, and anaerobic ammonia oxidation. The results showed that bacteria dominated the metagenomic library, accounting for 98.02% of all the sequences. Across all domains, the most common pathway was ammonia assimilation. For example, an average of 2830 ammonia assimilation pathway genes were detected for every million annotated bacterial sequences. In comparison, nitrogen fixation and anaerobic ammonia oxidation were the least detected pathways, accounting for 28.3 and 10.7 per million sequences, respectively. Different microorganisms can participate in a same nitrogen metabolism pathway, and the community structure of different soils was variable. The five typical forest soils in China show the same microbial nitrogen metabolism pathway traits; however, the community structure of the microorganisms mediating these processes was found to vary.