Decoding the fundamental taxa that decompose crop rhizodeposits (rhizo-C) and/or straw residue (straw-C) is crucial for understanding the role of plant-derived carbon (C) in driving microbial community assembly and consequent C decomposition. Here, a parallel C-labeling design, DNA-SIP, and metagenomics techniques were combined to separate maize rhizo-C utilizers from straw-C utilizers in agriculture soils containing both C sources. Also, by comparing bacterial utilizers and their C metabolisms in soils amended with a single C source (e.g., straw-C only) and two C sources (e.g., straw-C and rhizo-C), we investigated the shift of composition and metabolisms of soil bacterial utilizers responding to C sources shift (e.g., compositional and metabolic changes of straw-C utilizers from soil containing straw-C to soil containing both straw-C and rhizo-C). We revealed i) Proteobacteria predominantly utilized rhizo-C, while Firmicutes dominated the community specializing in straw-C decomposition in soil containing both straw-C and rhizo-C; ii) the planted maize (i.e. rhizo-C input) changed community composition and metabolisms of straw-C utilizers, which shifted from K-strategists characterized by an enrichment of lignin-degrading genes to r-strategists which exhibited an enrichment of genes related to polysaccharide degradation. This metabolic shift of straw-C utilizer ultimately reduced straw-C mineralization by 25.6% when maize was planted. This study identified the distinct utilizers of rhizo-C and straw-C in soils containing both C sources, and shed light on the shift of bacterial community and their metabolic activities responding to the changes of maize-derived C sources.

中文翻译：

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依赖玉米根际沉积物和秸秆碳源的微生物类群和代谢的转变


解码分解作物根际沉积物 (rhizo-C) 和/或秸秆残留物 (straw-C) 的基本分类群对于理解植物源碳 (C) 在驱动微生物群落组装和随后的碳分解中的作用至关重要。在这里，平行 C 标记设计、DNA-SIP 和宏基因组技术相结合，在含有两种碳源的农业土壤中将玉米根际碳利用者与秸秆碳利用者分开。此外，通过比较用单一碳源（例如仅秸秆碳）和两种碳源（例如秸秆碳和根茎碳）改良的土壤中的细菌利用者及其碳代谢，我们研究了组成和代谢的变化响应碳源的土壤细菌利用者的变化（例如，秸秆碳利用者的组成和代谢变化从含有秸秆碳的土壤到含有秸秆碳和根茎碳的土壤）。我们发现，i) 变形菌主要利用根际碳，而厚壁菌门则在专门从事含有秸秆碳和根际碳的土壤中分解秸秆碳的群落中占主导地位； ii) 种植的玉米（即根茎-C输入）改变了秸秆-C利用者的群落组成和代谢，从以富集木质素降解基因为特征的K-策略转变为以富集木质素降解基因为特征的r-策略。多糖降解。当种植玉米时，秸秆碳利用者的这种代谢转变最终使秸秆碳矿化减少了 25.6%。这项研究确定了含有两种碳源的土壤中根际碳和秸秆碳的不同利用者，并揭示了细菌群落的变化及其代谢活动对玉米碳源变化的响应。