School of Integrative Plant Science, Cornell University, Ithaca, NY 14853.
Department of Microbiome Science, Max Planck Institute for Developmental Biology, 72076 Tübingen, Germany.
Proc Natl Acad Sci U S A. 2021 Nov 23;118(47). doi: 10.1073/pnas.2115292118.
Soil microorganisms determine the fate of soil organic matter (SOM), and their activities compose a major component of the global carbon (C) cycle. We employed a multisubstrate, DNA-stable isotope probing experiment to track bacterial assimilation of C derived from distinct sources that varied in bioavailability. This approach allowed us to measure microbial contributions to SOM processing by measuring the C assimilation dynamics of diverse microorganisms as they interacted within soil. We identified and tracked 1,286 bacterial taxa that assimilated C in an agricultural soil over a period of 48 d. Overall C-assimilation dynamics of bacterial taxa, defined by the source and timing of the C they assimilated, exhibited low phylogenetic conservation. We identified bacterial guilds composed of taxa that had similar C assimilation dynamics. We show that C-source bioavailability explained significant variation in both C mineralization dynamics and guild structure, and that the growth dynamics of bacterial guilds differed significantly in response to C addition. We also demonstrate that the guild structure explains significant variation in the biogeographical distribution of bacteria at continental and global scales. These results suggest that an understanding of in situ growth dynamics is essential for understanding microbial contributions to soil C cycling. We interpret these findings in the context of bacterial life history strategies and their relationship to terrestrial C cycling.
土壤微生物决定了土壤有机物质（SOM）的命运，它们的活动构成了全球碳（C）循环的主要组成部分。我们采用多底物、DNA 稳定同位素探测实验来追踪源自不同生物可利用性来源的 C 的细菌同化。这种方法允许我们通过测量土壤中各种微生物相互作用时的 C 同化动态，来测量微生物对 SOM 处理的贡献。我们在 48 天的时间里，在一个农业土壤中鉴定和跟踪了 1286 种能够同化 C 的细菌分类群。根据它们同化的 C 的来源和时间，细菌分类群的整体 C 同化动态表现出较低的系统发育保守性。我们确定了由具有相似 C 同化动态的分类群组成的细菌菌群。我们表明，C 源生物利用度解释了 C 矿化动态和菌群结构的显著变化，并且细菌菌群的生长动态对 C 添加的响应存在显著差异。我们还证明，菌群结构解释了细菌在大陆和全球尺度上的生物地理分布的显著变化。这些结果表明，理解原位生长动态对于理解微生物对土壤 C 循环的贡献至关重要。我们根据细菌生活史策略及其与陆地 C 循环的关系来解释这些发现。
