Giannopoulos Georgios, Hartop Katherine R, Brown Bonnie L, Song Bongkeun, Elsgaard Lars, Franklin Rima B
Department of Biology, Virginia Commonwealth University, Richmond, VA, United States.
Department of Biological Sciences, University of New Hampshire, Durham, NH, United States.
Front Microbiol. 2020 Sep 30;11:560861. doi: 10.3389/fmicb.2020.560861. eCollection 2020.
We investigated the effects of trace metal additions on microbial nitrogen (N) and carbon (C) cycling using freshwater wetland sediment microcosms amended with micromolar concentrations of copper (Cu), molybdenum (Mo), iron (Fe), and all combinations thereof. In addition to monitoring inorganic N transformations (NO , NO , NO, NH ) and carbon mineralization (CO, CH), we tracked changes in functional gene abundance associated with denitrification (, , ), dissimilatory nitrate reduction to ammonium (DNRA; ), and methanogenesis (). With regards to N cycling, greater availability of Cu led to more complete denitrification (i.e., less NO accumulation) and a higher abundance of the and genes, which encode for Cu-dependent reductases. In contrast, we found sparse biochemical evidence of DNRA activity and no consistent effect of the trace metal additions on gene abundance. With regards to C mineralization, CO production was unaffected, but the amendments stimulated net CH production and Mo additions led to increased gene abundance. These findings demonstrate that trace metal effects on sediment microbial physiology can impact community-level function. We observed direct and indirect effects on both N and C biogeochemistry that resulted in increased production of greenhouse gasses, which may have been mediated through the documented changes in microbial community composition and shifts in functional group abundance. Overall, this work supports a more nuanced consideration of metal effects on environmental microbial communities that recognizes the key role that metal limitation plays in microbial physiology.
我们使用添加了微摩尔浓度铜（Cu）、钼（Mo）、铁（Fe）及其所有组合的淡水湿地沉积物微观模型，研究了痕量金属添加对微生物氮（N）和碳（C）循环的影响。除了监测无机氮转化（NO 、NO 、NO、NH ）和碳矿化（CO、CH）外，我们还追踪了与反硝化作用（ 、 、 ）、异化硝酸盐还原为铵（DNRA； ）和甲烷生成（ ）相关的功能基因丰度的变化。关于氮循环，更多的铜可用性导致更完全的反硝化作用（即更少的NO积累）以及编码铜依赖性还原酶的 和 基因的丰度更高。相比之下，我们发现DNRA活性的生化证据很少，并且痕量金属添加对 基因丰度没有一致的影响。关于碳矿化，CO产生不受影响，但添加物刺激了净CH产生，并且添加Mo导致 基因丰度增加。这些发现表明痕量金属对沉积物微生物生理学的影响会影响群落水平的功能。我们观察到对氮和碳生物地球化学的直接和间接影响，这导致温室气体产量增加，这可能是通过记录的微生物群落组成变化和功能组丰度变化介导的。总体而言，这项工作支持对金属对环境微生物群落的影响进行更细致入微的考虑，认识到金属限制在微生物生理学中所起的关键作用。
