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.