Favela, A. | Search bioRxiv

bioRxiv2026

Soil microbial diversity alters soil microhydrology through extracellular polymeric substance production

Soil microbial communities have a variety of mechanisms to deal with emerging drought stress. One well-documented mechanism is increased microbial production of extracellular polymeric substances (EPS), which can potentially change the soil density and water holding capacity. Yet little is known about how microbial diversity influences the functional capacity of EPS formation and the resulting outcomes in water dynamics. To understand more about communal microbiome EPS production, we set up sterile mesocosms where we examined the effects of microbial diversity (high or low treatments) and nutrient input (supplement or deficient treatments) on these processes. To capture the microhydrology of the mesocosms, we measured water holding (WH), infiltration, evaporation, and soil properties we believe microbes are altering (EPS, soil aggregation). Our hypothesis stated that if diversity was artificially manipulated, then soil-water properties will be altered via production of EPS. We predicted that low diversity systems would have lower functional diversity, leading to less EPS production, moisture storage, and minimal changes from inert soil media. As predicted, we found that the high-diversity systems had a higher water retention and lower rates of water loss over time than low-diversity systems. This trend was magnified in the nutrient-supplemented treatment, suggesting that EPS production and subsequent water-holding traits are emergent features of the microbiome. Unexpectedly, we observed a correlation between the amount of water retained and the quantity of lipid EPS produced. This suggests that EPS composition, rather than quantity, is determinative of a biofilms function. In conclusion, it appears that microbial diversity influences soil properties that are important to moisture retention within these systems. To date, the role that microbes and their diversity play in soil hydrology has been severely understudied, so this work aims to build ecological understandings of these systems. These findings are valuable, for if we learn how microbes manipulate soil moisture, we can apply these functions to advance sustainable agricultural practices and enhance ecosystem resilience to water scarcity in arid regions. Open Research StatementUpon publication data, and code will be made available through Zenodo. Sequencing data will be uploaded to NCBI SRA.

ecology↗

bioRxiv2023

Genetic variation exists within Zea mays to influence unsustainable nitrogen cycling microbiome function

Overuse of synthetic nitrogen fertilizers in agroecosystems causes environmental pollution and human harm at a global level. Nitrogenous fertilizers provide a short-lived benefit to crops in the agroecosystem, but stimulate microbially-mediated nitrification and denitrification, processes that result in N pollution, greenhouse gas (GHG) production, and reduced soil fertility. Recent advances in plant microbiome science suggest that plants can modulate the composition and activity of rhizosphere microbial communities. These rhizosphere communities act as an extended phenotype, primed by genetic variation in the plant host. Genetic variation in traits (e.g., plant secondary metabolites, root architecture, immune system, etc.) act as mechanistic selective agents on the composition of the microbiome. Here we attempted to determine whether genetic variation exists in Zea mays for the ability to influence the extended phenotype of rhizosphere soil microbiome composition and function. Specifically, we determined whether plants influence on soil nitrogen cycling activities was altered by plant genetics and thereby allowing it to be incorporated into breeding practices. To capture an extensive amount of genetic diversity within maize we sampled the rhizosphere microbiome of a germplasm chronosequence that included ex-PVP inbreds, hybrids, and teosinte (Z. mays ssp. mexicana and Z. mays ssp. parviglumis). We observed that potential N cycling processes were influenced by plant genetics. Teosinte and some hybrid genotypes supported microbial communities with lower potential nitrification and potential denitrification activity in the rhizosphere, while inbreds stimulated/did not inhibit these undesirable N-cycling activities. These potential differences translated to functional differences in N2O production, with teosinte plots producing less GHG than maize plots. Furthermore, within these Zea cultivars we found that plant genetics explained a significant amount of variation in the microbiome, particularly among different nitrification and denitrification functional genes within the community. We found that potential nitrification, potential incomplete denitrification, and overall denitrification rates, but not abundance of N-cycling genes of rhizosphere soils were influenced by growth stage and plant genetics. Taken together, these results suggest that crop selection can lead to changes in root phenotypes that could suppress unsustainable N-cycling processes. Reintroducing stress-adapted and "wild" root characteristics into modern germplasm may be a way to manipulate soil microbiomes at both a composition and functional level to improve sustainability.

ecology↗