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.