Microbial Diversity in Cerrado Biome (Neotropical Savanna) Soils.

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.

Combining "omics" strategies to analyze the biotechnological potential of complex microbial environments.

It is well established in the scientific literature that only a small fraction of microorganisms can be cultured by conventional microbiology methods. The ever cheaper and faster DNA sequencing methods, together with advances in bioinformatics, have improved our understanding of the structure and functional behavior of microbial communities in many complex environments. However, the metagenomics approach alone cannot elucidate the functionality of all microorganisms, because a vast number of potentially new genes have no homologs in public databases. Metatranscriptomics and metaproteomics are approaches based on different techniques and have recently emerged as promising techniques to describe microbial activities within a given environment at the molecular level. In this review, we will discuss current developments and applications of metagenomics, metatranscriptomics and metaproteomics, and their limitations in the study of microbial communities. The combined analysis of genes, mRNA and protein in complex microbial environments will be key to identify novel biological molecules for biotechnological purposes.