Rhizosphere Processes Group, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland.
Functional Genomics Center Zurich, ETH Zurich/University of Zurich, Zurich, Switzerland.
Glob Chang Biol. 2021 Apr;27(7):1365-1386. doi: 10.1111/gcb.15492. Epub 2021 Feb 3.
Climate change is strongly affecting high-mountain soils and warming in particular is associated with pronounced changes in microbe-mediated C and N cycling, affecting plant-soil interactions and greenhouse gas balances and therefore feedbacks to global warming. We used shotgun metagenomics to assess changes in microbial community structures, as well as changes in microbial C- and N-cycling potential and stress response genes and we linked these data with changes in soil C and N pools and temperature-dependent measurements of bacterial growth rates. We did so by incubating high-elevation soil from the Swiss Alps at 4°C, 15°C, 25°C, or 35°C for 1 month. We found no shift with increasing temperature in the C-substrate-degrader community towards taxa more capable of degrading recalcitrant organic matter. Conversely, at 35°C, we found an increase in genes associated with the degradation and modification of microbial cell walls, together with high bacterial growth rates. Together, these findings suggest that the rapidly growing high-temperature community is fueled by necromass from heat-sensitive taxa. This interpretation was further supported by a shift in the microbial N-cycling potential towards N mineralization and assimilation under higher temperatures, along with reduced potential for conversions among inorganic N forms. Microbial stress-response genes reacted inconsistently to increasing temperature, suggesting that the high-temperature community was not severely stressed by these conditions. Rather, soil microbes were able to acclimate by changing the thermal properties of membranes and cell walls as indicated by an increase in genes involved in membrane and cell wall modifications as well as a shift in the optimum temperature for bacterial growth towards the treatment temperature. Overall, our results suggest that high temperatures, as they may occur with heat waves under global warming, promote a highly active microbial community capable of rapid mineralization of microbial necromass, which may transiently amplify warming effects.
气候变化强烈影响高山土壤，特别是变暖与微生物介导的 C 和 N 循环的显著变化有关，影响植物-土壤相互作用和温室气体平衡，从而对全球变暖产生反馈。我们使用鸟枪法宏基因组学来评估微生物群落结构的变化，以及微生物 C 和 N 循环潜力和应激反应基因的变化，我们将这些数据与土壤 C 和 N 库的变化以及与温度相关的细菌生长速率测量结果联系起来。我们通过在 4°C、15°C、25°C 或 35°C 下孵育来自瑞士阿尔卑斯山的高海拔土壤 1 个月来实现这一点。我们没有发现随着温度升高，C 底物降解物群落向更能降解难降解有机物的类群转移。相反，在 35°C 时，我们发现与降解和修饰微生物细胞壁相关的基因增加，同时细菌生长速率很高。这些发现表明，快速增长的高温群落是由热敏类群的腐殖质提供燃料的。这一解释得到了进一步支持，即随着温度升高，微生物 N 循环潜力向 N 矿化和同化转变，同时无机 N 形态之间的转化潜力降低。微生物应激反应基因对温度升高的反应不一致，这表明高温群落没有受到这些条件的严重压力。相反，土壤微生物能够通过改变膜和细胞壁的热特性来适应，这表现在参与膜和细胞壁修饰的基因增加，以及细菌生长的最适温度向处理温度的转变。总的来说，我们的研究结果表明，高温，如全球变暖下热浪可能出现的情况，促进了一个高度活跃的微生物群落，能够快速矿化微生物腐殖质，这可能暂时放大变暖效应。
