Study of the structural and functional diversity of microbial communities in Uruguayan soils with respect to phosphorus phytoavailability

Doctoral thesis abstract

Abstract

Phosphorus (P) is essential for plant growth; its excessive use as a fertilizer in agricultural intensification has negatively impacted the environment and the economy. Soil microorganisms play a key role in P cycling, mediating its phytoavailability through enzymatic mechanisms. In this thesis, we studied: a) the structural diversity of prokaryotic communities in five soil units with different parent materials and nutritional status; b) the functional profiles of these communities linked to P cycling and their relationship with soil physicochemical properties; c) the distribution and abundance of eight key enzymes of P cycling in grasslands of Uruguay and the world. Prokaryotic communities were studied using a metagenomic approach (16S rRNA gene and total metagenome). The main results were: a) Soil structure, nutrient content, and water retention capacity influence the composition of prokaryotic communities, composed mainly of Archaea, Firmicutes, Acidobacteria, Actinobacteria and Verrucomicrobia, with variations in their abundance according to soil type. b) Functional profiles of the communities were modeled by the same physicochemical properties as taxonomic diversity; functional diversity was lower than taxonomic diversity, suggesting functional redundancy. c) PhoD alkaline phosphatase was the most abundant and phylogenetically widely distributed enzyme, followed by Nsap-A and Nsap-C acid phosphatases. A strong association was found between the abundance and diversity of genes encoding these three enzymes and pH, maximum temperature and evapotranspiration. The results indicate that structural and functional prokaryotic diversity is influenced by soil physicochemical properties and environmental variables, making its understanding essential for the sustainable management of the P cycle in agroecosystems of the Campos biome.