The Cerrado, the largest savanna region in South America, is located in central Brazil. Cerrado physiognomies, which range from savanna grasslands to forest formations, combined with the highly weathered, acidic clay Cerrado soils form a unique ecoregion. In this study, high-throughput sequencing of ribosomal RNA genes was combined with shotgun metagenomic analysis to explore the taxonomic composition and potential functions of soil microbial communities in four different vegetation physiognomies during both dry and rainy seasons. Our results showed that changes in bacterial, archaeal, and fungal community structures in cerrado denso, cerrado sensu stricto, campo sujo, and gallery forest soils strongly correlated with seasonal patterns of soil water uptake. The relative abundance of AD3, WPS-2, Planctomycetes, Thermoprotei, and Glomeromycota typically decreased in the rainy season, whereas the relative abundance of Proteobacteria and Ascomycota increased. In addition, analysis of shotgun metagenomic data revealed a significant increase in the relative abundance of genes associated with iron acquisition and metabolism, dormancy, and sporulation during the dry season, and an increase in the relative abundance of genes related to respiration and DNA and protein metabolism during the rainy season. These gene functional categories are associated with adaptation to water stress. Our results further the understanding of how tropical savanna soil microbial communities may be influenced by vegetation covering and temporal variations in soil moisture.

Savannas can be found in North and South America, Africa, Asia, and Oceania. The Cerrado is a vast savanna located mainly in the central region of Brazil. Although, Cerrado ecosystems are similar in vegetation structure, differences in soil characteristics influence the microbiota. Throughout the world savannas are rapidly being converted to agricultural and urban uses, altering physical and chemical properties of the soil, as well as microbial diversity through changes in bacterial and fungal richness, community structure, and activity. The studies addressed in this review describe soil microbial communities present in Cerrado ecosystems, which are dominated by Acidobacteria, Proteobacteria, and Actinobacteria. We highlight the importance of microbial communities to ecosystem services such as nutrient cycling, regulation of biogeochemical processes, and contribution to net primary production. Sustainable development based on the use of natural resources requires a better understanding of the microbial processes and genetic resources in this biome.