Diversidade genética da comunidade microbiana de drenagem ácida de mina em formação

Abstract

Acid mine drainage (AMD) is characterized by an acid runoff originated by chemical weathering of metal sulfide-rich rocks together with the chemolithotroph metabolism of some specialized microorganisms inhabiting these minerals. Despite having been studied for many decades, much remains unknown about the microbial community dynamics in AMD sites, especially their composition during their early development, when the acidity is moderate. In this context, this thesis is focused on the application of “OMICs” tools (metagenomics and single cell genomics) to try to solve this issue. In summary, in the first chapter we used the sequencing of 16S rRNA gene to describe the microbiota of AMD in their early stages of formation. The AMD was sampled in two periods (april 2013 and july 2014) from a copper mine in north of Brazil. We observed that acid mine drainage is a unique ecosystem into the mine environment. The high concentration of copper in the sediment of this AMD is probably driving the microbial community to a low diversity. Some microorganisms exhibited a high abundance and persistence in the environment over the time, being part of the core microbiome of AMD samples described here: members of Archaea, candidate division TM7, Acidithiobacillus and Chitinophagaceae. Furthermore, to understand the role of Chitinophagaceae in this environment, the second chapter of this thesis aimed to analyze the draft genome assemblies from single cells that were retrieved from the same AMD described above. These cells belong to the genus Hydrotalea, and is closely related to H. flava. Some analysis suggests that all single-amplified genomes (SAGs) obtained formed two clades that may represent different strains. These cells have the genomic potential for denitrification, copper and other metal resistance. We recovered two co-existing CRISPR-cas systems across SAGs. This system is known as an adaptive and heritable immunity encoded by prokaryotes. We observed heterogeneity in the population regarding their CRISPR repertoire. Our results suggest that the Hydrotalea sp. population studied here is adjusting to a quickly changing selective pressure at the microhabitat scale, and a very likely form of this selective pressure is phage predation.