Synergies between mycorrhizal fungi and soil microbial communities increase plant nitrogen acquisition     
Hestrin et al., 2019

Nitrogen availability often restricts primary productivity in terrestrial ecosystems. Arbuscular mycorrhizal (AM) fungi are ubiquitous symbionts of terrestrial plants and can improve plant nitrogen acquisition, but have a limited ability to access organic nitrogen. Although other soil biota mineralize organic nitrogen into bioavailable forms, they may simultaneously compete for nitrogen, with unknown consequences for plant nutrition. Here, we show that synergies between the mycorrhizal fungus Rhizophagus irregularis and soil microbial communities have a highly non-additive effect on nitrogen acquisition by the model grass Brachypodium distachyon. These multipartite microbial synergies result in a doubling of the nitrogen that mycorrhizal plants acquire from organic matter and a tenfold increase in nitrogen acquisition compared to non-mycorrhizal plants grown in the absence of soil microbial communities. This previously unquantified multipartite relationship may contribute to more than 70 Tg of annually assimilated plant nitrogen, thereby playing a critical role in global nutrient cycling and ecosystem function.

 

Multipartite synergies between AM fungi and soil microbial communities increase plant biomass and N acquisition from organic matter. a Mesocosm design. b Plants acquired more N from organic matter in the presence of AM fungi and soil microbial communities. c Plants grown with both AM fungi and soil microbes acquired more N than expected based on the sum of N acquired by control plants and those grown with AM fungi or soil microbes alone. d AM colonization is associated with greater plant biomass. e AM plants grown with soil microbes derived a greater proportion of their total N from organic matter than control plants and plants grown with AM fungi or soil microbial communities alone. Significance levels are indicated with the following symbols: ·p < 0.1, *p < 0.05, **p < 0.01, ***p < 0.001 and denote the results of a Tukey’s HSD test performed on log-transformed data (b, d), an unpaired t test (c), and a Tukey’s HSD test performed on untransformed data (e). Error bars represent the standard error (n = 7 biologically independent samples)

https://www.nature.com/articles/s42003-019-0481-8