Diversidade filogenética e funcional do microbioma, com ênfase nos genes envolvidos no metabolismo do arsênio, de sedimento impactado por mineração

Abstract

The Iron Quadrangle (Minas Gerais, Brazil) is one of the worlds largest mining regions, being historically explored for over 300 years. Since then, many toxic metals and metalloids were released into the environment, leading to contamination of water bodies. Since prokaryotic community influences the bioavailability of these toxic elements and their importance in the ecological balance of various environments, we investigated the taxonomic and functional diversity in the microbiome from Mina Stream, historically metal-contaminated. Classical approache of cultivation - with emphasis on As-resistant bacteria and genes responsible for As transformation -, and metagenomic sequencing using next-generation platform were applied. One hundred and twenty-three bacterial isolates were identified as AsIII oxidizers and AsV reducers, represented by 20 genera. This study describes for the first time Thermomonas and Pannonibacter as As-transforming genera. Phenotypic characterization of isolates revealed that 72% were AsV reducers and 20% were AsIII oxidizers. In addition, the genotype characterization revealed the presence of arsC, arrA and aioA genes in the bacterial isolates: 85% of the isolates harbored arsC gene, 20% aioA gene and 7% arrA gene. Phylogenetic analysis of arsC and aioA genes obtained from the isolates and clones suggest that these isolates represent environmentally important bacteria acting on the As transformation. Moreover, taxonomic profile obtained by metagenome analysis revealed a complex community, with dominance of Proteobacteria and Parvarcheota. Bacterial and archaeal genomes were reconstructed based on SEED subsystems database, especially Candidatus Nitrospira defluvii and Nitrosopumilus maritimus. Their presence implicated them in C and N cycling in the MSS. Functional reconstruction revealed a large diverse set of genes for ammonium assimilation and ammonification. These processes have been implicated in the maintenance of N cycle of the sediment. Functional annotation unveiled a high diversity of metal resistance genes. Furthermore, a high metabolic diversity was detected in the sediment of Mina Stream, suggesting that the historical metal contamination is no longer affecting it. Finally, the results reported herein may contribute to expand the current knowledge of the microbial taxonomic and functional composition of metal-contaminated sediments.