Institute of Soil and Water Resources and Environmental Science, College of Environmental and Resource Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, 866 Yuhangtang Road, Hangzhou 310058, China.
Department of Environmental Science, University of Arizona, Tucson, AZ 85721, USA.
Sci Total Environ. 2024 Dec 1;954:176675. doi: 10.1016/j.scitotenv.2024.176675. Epub 2024 Oct 2.
Soil microbial life-history strategies, as indicated by rRNA operon (rrn) copy numbers, strongly influence agro-ecosystem functioning. Long-term N fertilization causes strong and lasting changes in soil properties, yet its impact on microbial strategies remains largely unexplored. Using long-term field experiments across three agro-ecosystems, we consistently found that N fertilization strongly decreased soil C: N ratio and pH, further increasing the community-level rrn copy number, including both average rrn copy number and total 16S rRNA copy number. Soil C: N stoichiometry balanced by N supplement favored the growth of N-dependent copiotrophic species containing high rrn copy numbers (an average of 2.5) and increased their network connections, predominantly contributing to community-level rrn copy number increase. Decreased soil pH caused by N fertilization also favored the growth of some species whose abundances negatively correlated with pH, partially contributing to the community-level rrn copy number increase. By examining the genomes of two dominant species, we found that microorganisms with a higher rrn copy number (6), e.g., Streptomyces scabiei, possessed more genes related to C and N transport and metabolism. In contrast, the Mycobacterium simiae with a lower rrn copy number (1) has more genes associated with secondary metabolite biosynthesis and lipid transport and metabolism. Our finding challenges the concept of microbial life-strategy regulation solely by nutrient availability, highlighting the important contributions of soil stoichiometric balance and pH to microbial strategies in agro-ecosystems under long-term N inputs.
土壤微生物的生活史策略（通过 rRNA 操纵子（rrn）的拷贝数来指示）强烈影响农业生态系统的功能。长期施氮会导致土壤性质发生强烈而持久的变化，但它对微生物策略的影响在很大程度上仍未得到探索。本研究利用三个农业生态系统的长期田间实验，一致发现氮施肥强烈降低了土壤 C:N 比和 pH 值，进一步增加了群落水平的 rrn 拷贝数，包括平均 rrn 拷贝数和总 16S rRNA 拷贝数。氮补充平衡土壤 C:N 化学计量有利于依赖氮的富营养型物种的生长，这些物种含有高 rrn 拷贝数（平均为 2.5），并增加了它们的网络连接，主要导致群落水平 rrn 拷贝数增加。氮施肥导致的土壤 pH 值降低也有利于一些丰度与 pH 值呈负相关的物种的生长，部分导致群落水平 rrn 拷贝数增加。通过研究两个优势物种的基因组，我们发现 rrn 拷贝数较高（6）的微生物，例如疮痂链霉菌，具有更多与 C 和 N 运输和代谢相关的基因。相比之下，rrn 拷贝数较低（1）的耻垢分枝杆菌具有更多与次生代谢物生物合成以及脂质运输和代谢相关的基因。我们的发现挑战了微生物生活史策略仅由养分可用性调节的概念，强调了土壤化学计量平衡和 pH 值对农业生态系统中长期氮输入下微生物策略的重要贡献。
