Arbuscular mycorrhizal fungi (AMF) are important symbionts of many plant species, facilitating the acquisition of soil nutrients by roots. We hypothesized that AMF root colonization is strongly influenced by the composition of the soil microbiome. Here, we evaluated mycorrhizal colonization of two plants, the grass Urochloa brizantha (Brachiaria) and the legume Crotalaria juncea (Crotalaria). These were cultivated in the same soil but hosting eight distinct microbiomes: natural soil (i); soil exposed to heat treatments for 1 h at 50 ºC (ii), 80 ºC (iii), or 100 ºC (iv); sterilized soil by autoclaving (AS) followed by re-inoculation of dilutions of the natural soil community at 10⁻¹ (v), 10⁻³ (vi), and 10⁻⁶ (vii); and AS without re-inoculation (viii). Microbial diversity (bacteria and fungi) was assessed through 16S rDNA and ITS1 metabarcoding, respectively, and the soil acid phosphatase activity (AP_ASE) was measured. Sequencing results showed the formation of distinct microbial communities according to the soil manipulations, which also correlated with the decline of AP_ASE. Subsequently, seedlings of Brachiaria and Crotalaria were grown in those soils inoculated separately with three AMF (Acaulospora colombiana, Rhizophagus clarus, and Dentiscutata heterogama) which were compared to an AMF-free control treatment. Brachiaria showed higher colonization in natural soil when compared to the microbial community manipulations, regardless of the AMF species inoculated. In contrast, two mycorrhiza species were able to colonize Crotalaria under modified microbial communities at similar rates to natural soil. Furthermore, Brachiaria showed a possible inverse relationship between AP_ASE and mycorrhization, but this trend was absent for Crotalaria. We conclude that mycorrhizal root colonization and soil acid phosphatase activity were associated with the structure of the soil microbiome, depending on the plant species evaluated.

丛枝菌根真菌 (AMF) 是许多植物物种的重要共生体，有助于根系获取土壤养分。我们假设 AMF 根的定植受土壤微生物组组成的强烈影响。在这里，我们评估了两种植物的菌根定植，这两种植物是草Urochloa brizantha ( Brachiaria ) 和豆科植物Crotalaria juncea ( Crotalaria )。它们在相同的土壤中种植，但拥有八种不同的微生物组：天然土壤 (i)；暴露于 50 ºC (ii)、80 ºC (iii) 或 100 ºC (iv) 热处理 1 小时的土壤；通过高压灭菌 (AS) 灭菌的土壤，然后在 10 ^-1 (v), 10 ^-3重新接种稀释的天然土壤群落(vi) 和 10 ^-6 (vii)；和 AS 无需重新接种 (viii)。分别通过 16S rDNA 和 ITS1 元条形码评估微生物多样性（细菌和真菌），并测量土壤酸性磷酸酶活性（AP _ASE）。测序结果显示根据土壤操作形成了不同的微生物群落，这也与 AP _ASE的下降有关。随后，将Brachiaria和Crotalaria 的幼苗在分别接种了三种 AMF（Acaulospora colombiana、Rhizophagus clarus和Dentiscutata heterogama）的那些土壤中生长，并与不含AMF 的对照处理进行比较。与微生物群落操作相比，臂菌在天然土壤中的定植率更高，无论接种的 AMF 种类如何。相比之下，两种菌根物种能够以与天然土壤相似的速率在改良的微生物群落下定植Crotalaria。此外，Brachiaria显示 AP _ASE和菌根之间可能存在负相关关系，但Crotalaria不存在这种趋势。我们得出结论，菌根根系定植和土壤酸性磷酸酶活性与土壤微生物组的结构有关，这取决于所评估的植物物种。