Wittorf Lea, Bonilla-Rosso Germán, Jones Christopher M, Bäckman Ola, Hulth Stefan, Hallin Sara
Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
Environ Microbiol Rep. 2016 Aug;8(4):486-92. doi: 10.1111/1758-2229.12393. Epub 2016 Mar 21.
Denitrification is of global significance for the marine nitrogen budget and the main process for nitrogen loss in coastal sediments. This facultative anaerobic respiratory pathway is modular in nature and the final step, the reduction of nitrous oxide (N2 O), is performed by microorganisms with a complete denitrification pathway as well as those only capable of N2 O reduction. Fluctuating oxygen availability is a significant driver of denitrification in sediments, but the effects on the overall N2 O-reducing community that ultimately controls the emission of N2 O from marine sediments is not well known. To investigate the effects of different oxygen regimes on N2 O reducing communities, coastal marine surface sediment was incubated in microcosms under oxic, anoxic or oscillating oxygen conditions in the overlying water for 137 days. Quantification of the genetic potential for denitrification, anammox and respiratory ammonification indicated that denitrification supported nitrogen removal in these sediments. Furthermore, denitrifiers with a complete pathway were identified as the dominant community involved in N2 O reduction, rather than organisms that are only N2 O reducers. Specific lineages within each group were associated with different oxygen regimes suggesting that oxygen availability in the overlying water is associated with habitat partitioning of N2 O reducers in coastal marine surface sediments.
反硝化作用对海洋氮收支具有全球意义，是沿海沉积物中氮损失的主要过程。这种兼性厌氧呼吸途径本质上是模块化的，最后一步，即一氧化二氮（N2O）的还原，由具有完整反硝化途径的微生物以及仅能进行N2O还原的微生物来完成。波动的氧可利用性是沉积物中反硝化作用的一个重要驱动因素，但对最终控制海洋沉积物中N2O排放的整个N2O还原群落的影响尚不清楚。为了研究不同氧条件对N2O还原群落的影响，将沿海海洋表层沉积物在覆盖水的有氧、缺氧或振荡氧条件下的微宇宙中培养137天。对反硝化作用、厌氧氨氧化和呼吸性氨化的遗传潜力进行定量分析表明，反硝化作用有助于这些沉积物中的氮去除。此外，具有完整途径的反硝化细菌被确定为参与N2O还原的主要群落，而不是仅能进行N2O还原的生物体。每组中的特定谱系与不同的氧条件相关，这表明覆盖水中的氧可利用性与沿海海洋表层沉积物中N2O还原菌的生境划分有关。
