Department of Ecological Microbiology, University of Bayreuth, 95440 Bayreuth, Germany.
Appl Environ Microbiol. 2010 Feb;76(4):1125-34. doi: 10.1128/AEM.02256-09. Epub 2009 Dec 18.
Wetlands are sources of denitrification-derived nitrous oxide (N2O). Thus, the denitrifier community of an N2O-emitting fen (pH 4.7 to 5.2) was investigated. N2O was produced and consumed to subatmospheric concentrations in unsupplemented anoxic soil microcosms. Total cell counts and most probable numbers of denitrifiers approximated 10(11) cells x g(DW)(-1) (where DW is dry weight) and 10(8) cells x g(DW)(-1), respectively, in both 0- to 10-cm and 30- to 40-cm depths. Despite this uniformity, depth-related maximum reaction rate (v(max)) values for denitrification in anoxic microcosms ranged from 1 to 24 and -19 to -105 nmol N2O h(-1) x g(DW)(-1), with maximal values occurring in the upper soil layers. Denitrification was enhanced by substrates that might be formed via fermentation in anoxic microzones of soil. N2O approximated 40% of total nitrogenous gases produced at in situ pH, which was likewise the optimal pH for denitrification. Gene libraries of narG and nosZ (encoding nitrate reductase and nitrous oxide reductase, respectively) from fen soil DNA yielded 15 and 18 species-level operational taxonomic units, respectively, many of which displayed phylogenetic novelty and were not closely related to cultured organisms. Although statistical analyses of narG and nosZ sequences indicated that the upper 20 cm of soil contained the highest denitrifier diversity and species richness, terminal restriction fragment length polymorphism analyses of narG and nosZ revealed only minor differences in denitrifier community composition from a soil depth of 0 to 40 cm. The collective data indicate that the regional fen harbors novel, highly diverse, acid-tolerant denitrifier communities capable of complete denitrification and consumption of atmospheric N2O at in situ pH.
湿地是反硝化衍生的氧化亚氮（N2O）的来源。因此，对排放 N2O 的沼泽（pH 值为 4.7 至 5.2）的反硝化生物群落进行了研究。在未补充缺氧土壤微宇宙中，N2O 以亚大气浓度产生和消耗。总细胞计数和最可能的反硝化计数分别约为 10（11）细胞 x g（DW）（-1）（其中 DW 是干重）和 10（8）细胞 x g（DW）（-1），在 0 至 10 厘米和 30 至 40 厘米的深度。尽管如此，缺氧微宇宙中反硝化的深度相关最大反应速率（v（max））值范围为 1 至 24 和-19 至-105 nmol N2O h（-1）x g（DW）（-1），最大值出现在上层土壤中。反硝化作用受到可能通过土壤缺氧微区发酵形成的基质的增强。在原位 pH 下，N2O 约占总含氮气体的 40%，这也是反硝化的最佳 pH 值。来自沼泽土壤 DNA 的 narG 和 nosZ（分别编码硝酸还原酶和氧化亚氮还原酶）的基因文库分别产生了 15 种和 18 种种水平的操作分类单位，其中许多具有系统发育新颖性，与培养的生物体没有密切关系。尽管 narG 和 nosZ 序列的统计分析表明，土壤的上层 20 厘米含有最高的反硝化生物多样性和物种丰富度，但 narG 和 nosZ 的末端限制性片段长度多态性分析仅表明从 0 到 40 厘米的土壤深度，反硝化生物群落组成存在微小差异。综合数据表明，该地区的沼泽地拥有新型、高度多样化、耐酸的反硝化生物群落，能够在原位 pH 下完成反硝化作用和消耗大气 N2O。
