Evidence of a selective and bi‐directional relationship between arbuscular mycorrhizal fungal and bacterial communities co‐inhabiting plant roots

Abstract

Arbuscular mycorrhizal fungi (AMF) provide plants with vital mineral nutrients and co‐exist inside the roots alongside a complex community of bacterial endophytes. These co‐existing AMF and bacterial root communities have been studied individually and are known to be influenced in structure by different environmental parameters. However, the extent to which they are affected by environmental parameters and by each other is completely unknown. The current study addressed this knowledge gap by characterising AMF and bacterial communities inside plant roots from a natural and an agricultural ecosystem. Using multivariate modelling, the relative contribution of environmental parameters in structuring the two communities was quantified at different spatial scales. Using this model, it was possible to then remove the contribution of environmental parameters and show that the co‐existing AMF and bacterial communities were significantly correlated with each other, explaining up to 36% of each other's variance. Notably, this was not due to the presence of know AMF endobacteria, as removal of endobacterial reads maintained the significance of correlation. These findings provide the first empirical evidence of a selective and bi‐directional relationship between AMF and bacteria co‐inhibiting plant roots and indicate that a significant fraction of this covariation is due to biological and ecological interactions between them.

Spores of arbuscular mycorrhizal fungi host surprisingly diverse communities of endobacteria

“…At Site 2 (dune), plant density was a significant driver of Ca Mg incidence in AMF spores, alongside Ca. Plant density (in the dunes) and soil P (in the agricultural grassland) were also important drivers of root endosphere AMF communities at these sites (Lastovetsky et al ., 2022); therefore, it is possible that by influencing the structure of AMF communities, the effect of plant density and P translated into Ca Mg distribution across AMF spores at these sites. It is important to note, however, that plant density in a dune environment is strongly correlated with distance from the beach, with density increasing with increasing distance, which was also the case in our study (Fig.…”

“…Detailed methods are described in Lastovetsky et al . (2022). In brief, soil pH was determined with a pH probe (WTW, Weilheim, Germany) using a 2 : 1 deionised water to soil mixture.…”

“…Soil chemistry analysis was performed at the Teagasc Soil laboratory at Johnstown Castle, Wexford, Ireland. Detailed methods are described in Lastovetsky et al (2022). In brief, soil pH was determined with a pH probe (WTW, Weilheim, Germany) using a 2 : 1 deionised water to soil mixture.…”

Phosphorus addition increases stability and complexity of co-occurrence network of soil microbes in an artificial Leymus chinensis grassland

“…The results of this study showed that phosphorus treatment increased the stability and complexity of the bacteria–fungi co-occurrence networks. We hypothesize that this difference may be attributed to the increase in and accumulation of soil nutrients, which promote cooperation between microbial communities ( Johnson, 2010 ; Trivedi et al, 2020 ; Lastovetsky et al, 2022 ). Among the keystone species in this study, Glomeromycotan is an arbuscular mycorrhizal fungus (AMF), and interactions between plants and AMF occur through the participation of many microorganisms that have positive effects on plant nutrient uptake.…”

Mycorrhizal research now: from the micro‐ to the macro‐scale

“…Spores of arbuscular mycorrhizal fungi harbor endobacteria. Based on field-collected spores, it appears that endobacterial communities inside individual fungal spores can be diverse, and a remarkable number of different bacteria can be found within Glomeromycotina spores (Lastovetsky et al, 2024(Lastovetsky et al, , in this issue pp. 1785(Lastovetsky et al, -1797.…”