Semiconductor Sequencing Reveals the Diversity of Bacterial Communities in an Amazonian Reservoir

Abstract

The reservoir of the Tucuruí hydropower plant has been reported to be a source of methane by several studies. These results question the Brazilian energy policy that plans to establish many other plants similar to Tucuruí in the Amazon region. In this study, we used a next-generation sequencing platform, the Ion Torrent Personal Genome Machine, and employed a barcode library to investigate the bacterial diversity along a 70-m deep water column in the proximity of the dam. One-litre water samples were taken at each 10 m from the surface to extract total DNA. A total of 1,505,461 reads were generated. The alpha diversity analyses showed 2,733, 2,280, 1,354, 1,338, 2,726, 2,134, 2,017, 1,885 operational taxonomic units (OTUs; 3% cutoff) at depths of 0, 10, 20,30, 40, 50, 60 and 70 m, respectively. Taxonomic inference analyses identified the most abundant phyla as being Proteobacteria, Cyanobacteria, Bacteroidetes, Acidobacteria and Actinobacteria, but others phyla were also found. This water column seems to produce oxygen in the upper layers due to abundance of Cyanobacteria. In the deeper layers, most of Proteobacterial sequences were assigned to Methanotrophic bacteria, showing that a significant amount of methane is consumed by these communities.

Insights Into Limnothrix sp. Metabolism Based on Comparative Genomics

“…Although the Brazilian Amazon is known to harbor vast biodiversity, cyanobacterial genomic data are scarce for this biome ( Rigonato et al, 2017 ). Previous metagenomic analysis conducted in Tucuruí Hydroelectric Reservoir (3°49′55″S, 49°38′50″W), which has an area of 1,783 km 2 of flooded primary Amazonian forest ( Fearnside, 2001 ) (Figure 1 ), revealed a high diversity of cyanobacteria ( Baraúna et al, 2013 ; Das Graças et al, 2015 ). The reservoir has little human interference in its water quality ( Curtarelli et al, 2016 ), and rainfall is the main source of nutrients when it is full, during the wet period from January to April; from March to December (the dry period) the nutrients are released from the lake bottom ( Pettersson and Pozdnyakov, 2013 ).…”