Department of Forest Mycology and Plant Pathology, Swedish University of Agricultural Sciences, Box 7026, 75007 Uppsala, Sweden.
Department of Plant Biology, Swedish University of Agricultural Science, Box 7080, 75007 Uppsala, Sweden.
FEMS Microbiol Ecol. 2022 Aug 23;98(9). doi: 10.1093/femsec/fiac092.
The rhizosphere is a hotspot for denitrification. The nitrous oxide (N2O) reductase among denitrifiers and nondenitrifying N2O reducers is the only known N2O sink in the biosphere. We hypothesized that the composition of root-associated N2O-reducing communities when establishing on annual crops depend on soil type and plant species, but that assembly processes are independent of these factors and differ between nosZ clades I and II. Using a pot experiment with barley and sunflower and two soils, we analyzed the abundance, composition, and diversity of soil and root-associated N2O reducing communities by qPCR and amplicon sequencing of nosZ. Clade I was more abundant on roots compared to soil, while clade II showed the opposite. In barley, this pattern coincided with N2O availability, determined as potential N2O production rates, but for sunflower no N2O production was detected in the root compartment. Root and soil nosZ communities differed in composition and phylogeny-based community analyses indicated that assembly of root-associated N2O reducers was driven by the interaction between plant and soil type, with inferred competition being more influential than habitat selection. Selection between clades I and II in the root/soil interface is suggested, which may have functional consequences since most clade I microorganisms can produce N2O.
根际是反硝化作用的热点区域。反硝化细菌和非反硝化的 N2O 还原酶中的亚硝酸盐还原酶是生物圈中唯一已知的 N2O 汇。我们假设，在一年生作物上定植时，与根相关的 N2O 还原群落的组成取决于土壤类型和植物物种，但组装过程不受这些因素的影响，并且在 nosZ 类群 I 和 II 之间存在差异。我们使用大麦和向日葵的盆栽实验和两种土壤，通过 qPCR 和 nosZ 扩增子测序分析了土壤和根相关 N2O 还原群落的丰度、组成和多样性。与土壤相比，类群 I 在根上更为丰富，而类群 II 则相反。在大麦中，这种模式与 N2O 的可用性一致，即潜在的 N2O 产生率，但在向日葵中，在根区未检测到 N2O 的产生。根和土壤的 nosZ 群落在组成和系统发育上存在差异，基于系统发育的群落分析表明，根相关 N2O 还原菌的组装受植物和土壤类型的相互作用驱动，推断出竞争比栖息地选择更为重要。在根/土壤界面之间存在对类群 I 和 II 的选择，这可能具有功能后果，因为大多数类群 I 的微生物可以产生 N2O。
