Inoculation with Stutzerimonas stutzeri strains decreases N_2O emissions from vegetable soil by altering microbial community composition and diversity

Inoculation with plant growth-promoting rhizobacteria (PGPR) strains has promoted plant growth and decreased nitrous oxide (N_2O) emissions from agricultural soils simultaneously. However, limited PGPR strains can mitigate N_2O emissions from agricultural soils, and the microbial ecological mechanisms underlying N_2O mitigation after inoculation are poorly understood. In greenhouse pot experiments, the effects of inoculation with Stutzerimonas stutzeri NRCB010 and NRCB025 on tomato growth and N_2O emissions were investigated in two vegetable agricultural soils with contrasting textures. Inoculation with NRCB010 and NRCB025 significantly promoted tomato growth in both soils. Moreover, inoculation with NRCB010 decreased the N_2O emissions from the fine- and coarse-textured soils by 38.7% and 52.2%, respectively, and inoculation with NRCB025 decreased the N_2O emissions from the coarse-textured soil by 76.6%. Inoculation with NRCB010 and NRCB025 decreased N_2O emissions mainly by altering soil microbial community composition and the abundance of nitrogen-cycle functional genes. The N_{2O-mitigating} effect might be partially explained by a decrease in the (amoA + amoB)/(nosZI + nosZII) and (nirS + nirK)/(nosZI + nosZII) ratios, respectively. Soil pH and organic matter were key variables that explain the variation in abundance of N-cycle functional genes and subsequent N_2O emission. Moreover, the N_{2O-mitigating} effect varied depending on soil textures and individual strain after inoculation. This study provides insights into developing biofertilizers with plant growth-promoting and N_{2O-mitigating} effects. IMPORTANCE Plant growth-promoting rhizobacteria (PGPR) have been applied to mitigate nitrous oxide (N_2O) emissions from agricultural soils, but the microbial ecological mechanisms underlying N_2O mitigation are poorly understood. That is why only limited PGPR strains can mitigate N_2O emissions from agricultural soils. Therefore, it is of substantial significance to reveal soil ecological mechanisms of PGPR strains to achieve efficient and reliable N_{2O-mitigating} effect after inoculation. Inoculation with Stutzerimonas stutzeri strains decreased N_2O emissions from two soils with contrasting textures probably by altering soil microbial community composition and gene abundance involved in nitrification and denitrification. Our findings provide detailed insight into soil ecological mechanisms of PGPR strains to mitigate N_2O emissions from vegetable agricultural soils.