Earthworms are known to improve plant growth in a soil-dependent way, notably via modifications of the rhizosphere microbiota and its functions. We tested the hypothesis that earthworms influence the abundance of microbial genes involved in N cycle according to the type of soil. In three soils with contrasting texture, we quantified five N-cycling genes in different microsites (bulk, rhizosphere or earthworm casts) of microcosms containing (i) neither plants nor eathworms, (ii) plants, (iii) earthworms, (iv) both plant and earthworms. In the presence of earthworms, rhizophere was enriched in nifH (N₂ fixation) and depressed in nosZ or narG (denitrification) in sandy soil, suggesting a shift in N balance towards immobilization; rhizosphere was enriched in nifH but also nosZ and narG in loamy soil; no effect was detected in clayey soil. The pattern of gene abundance across the different soils and microsites suggests that earthworms could favor microorganisms with a potential beneficial effect on plants specifically in sandy soils.

众所周知，蚯蚓能够以依赖于土壤的方式改善植物生长，特别是通过改变根际微生物群及其功能。我们测试了蚯蚓根据土壤类型影响参与氮循环的微生物基因丰度的假设。在三种具有对比质地的土壤中，我们量化了微观世界的不同微位点（块体、根际或蚯蚓铸件）中的五个氮循环基因，这些微观世界既不包含植物也不包含蚯蚓，（ii）植物，（iii）蚯蚓，（iv）两者植物和蚯蚓。_{在有蚯蚓存在的情况下，沙土中根际的 nifH（N 2固定）}富集，nosZ 或 narG（反硝化）减少，这表明氮平衡向固定化方向转变。壤质土壤中根际富含 nifH，但也富含 nosZ 和 narG；在粘土中没有检测到任何影响。不同土壤和微场所的基因丰度模式表明，蚯蚓可能有利于微生物，对植物特别是沙土中的植物产生潜在的有益影响。