McBride Steven G, Osburn Ernest D, Lucas Jane M, Simpson Julia S, Brown Taylor, Barrett J E, Strickland Michael S
Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, 40546, USA.
Department of Biological Sciences, Virginia Tech, Blacksburg, VA, 24061, USA.
Microb Ecol. 2023 Feb;85(2):659-668. doi: 10.1007/s00248-022-01967-0. Epub 2022 Jan 31.
Variation in microbial use of soil carbon compounds is a major driver of biogeochemical processes and microbial community composition. Available carbon substrates in soil include both low molecular weight-dissolved organic carbon (LMW-DOC) and volatile organic compounds (VOCs). To compare the effects of LMW-DOC and VOCs on soil chemistry and microbial communities under different moisture regimes, we performed a microcosm experiment with five levels of soil water content (ranging from 25 to 70% water-holding capacity) and five levels of carbon amendment: a no carbon control, two dissolved compounds (glucose and oxalate), and two volatile compounds (methanol and α-pinene). Microbial activity was measured throughout as soil respiration; at the end of the experiment, we measured extractable soil organic carbon and total extractable nitrogen and characterized prokaryotic communities using amplicon sequencing. All C amendments increased microbial activity, and all except oxalate decreased total extractable nitrogen. Likewise, individual phyla responded to specific C amendments-e.g., Proteobacteria increased under addition of glucose, and both VOCs. Further, we observed an interaction between moisture and C amendment, where both VOC treatments had higher microbial activity than LMW-DOC treatments and controls at low moisture. Across moisture and C treatments, we identified that Chloroflexi, Nitrospirae, Proteobacteria, and Verrucomicrobia were strong predictors of microbial activity, while Actinobacteria, Bacteroidetes, and Thaumarcheota strongly predicted soil extractable nitrogen. These results indicate that the type of labile C source available to soil prokaryotes can influence both microbial diversity and ecosystem function and that VOCs may drive microbial functions and composition under low moisture conditions.
土壤碳化合物微生物利用的变化是生物地球化学过程和微生物群落组成的主要驱动因素。土壤中可利用的碳底物包括低分子量溶解有机碳（LMW-DOC）和挥发性有机化合物（VOCs）。为了比较LMW-DOC和VOCs在不同水分条件下对土壤化学和微生物群落的影响，我们进行了一项微观实验，设置了五个土壤含水量水平（田间持水量的25%至70%）和五个碳添加水平：无碳对照、两种溶解化合物（葡萄糖和草酸盐）以及两种挥发性化合物（甲醇和α-蒎烯）。在整个实验过程中，通过土壤呼吸来测量微生物活性；在实验结束时，我们测量了可提取土壤有机碳和总可提取氮，并使用扩增子测序对原核生物群落进行了表征。所有碳添加都增加了微生物活性，除草酸盐外，所有添加物都降低了总可提取氮。同样，不同的门对特定的碳添加有不同反应——例如，在添加葡萄糖和两种VOCs的情况下，变形菌门增加。此外，我们观察到水分和碳添加之间存在相互作用，在低水分条件下，两种VOC处理的微生物活性均高于LMW-DOC处理和对照。在不同水分和碳处理中，我们发现绿弯菌门、硝化螺旋菌门（Nitrospirae）、变形菌门和疣微菌门是微生物活性的有力预测指标，而放线菌门、拟杆菌门和奇古菌门（Thaumarcheota）则强烈预测土壤可提取氮。这些结果表明，土壤原核生物可利用 的不稳定碳源类型可影响微生物多样性和生态系统功能，并且VOCs可能在低水分条件下驱动微生物功能和组成。
