Microbial communities in the deep-sea sediments of the South São Paulo Plateau, Southwestern Atlantic Ocean.

Microbial communities play a key role in the ocean, acting as primary producers, nutrient recyclers, and energy providers. The São Paulo Plateau is a region located on the southeastern coast of Brazil within economic importance, due to its oil and gas reservoirs. With this focus, this study examined the diversity and composition of microbial communities in marine sediments located at three oceanographic stations in the southern region of São Paulo Plateau using the HOV Shinkai 6500 in 2013. The 16S rRNA gene was sequenced using the universal primers (515F and 926R) by the Illumina Miseq platform. The taxonomic compositions of samples recovered from SP3 station were markedly distinct from those obtained from SP1 and SP2. Although all three stations exhibited a high abundance of Gammaproteobacteria (> 15%), this taxon dominated more than 90% of composition of the A and C sediment layers at SP3. The highest abundance of the archaeal class Nitrososphaeria was presented at SP1, mainly at layer C (~ 21%), being absent at SP3 station. The prediction of chemoheterotrophy and fermentation as important microbial functions was supported by the data. Additionally, other metabolic pathways related to the cycles of nitrogen, carbon and sulfur were also predicted. The core microbiome analysis comprised only two ASVs. Our study contributes to a better understanding of microbial communities in an economically important little-explored region. This is the third microbiological survey in plateau sediments and the first focused on the southern region.

Bacterial diversity in deep-sea sediments under influence of asphalt seep at the São Paulo Plateau.

Here we investigated the diversity of bacterial communities from deep-sea surface sediments under influence of asphalt seeps at the Sao Paulo Plateau using next-generation sequencing method. Sampling was performed at North São Paulo Plateau using the human occupied vehicle Shinkai 6500 and her support vessel Yokosuka. The microbial diversity was studied at two surficial sediment layers (0-1 and 1-4 cm) of five samples collected in cores in water depths ranging from 2456 to 2728 m. Bacterial communities were studied through sequencing of 16S rRNA gene on the Ion Torrent platform and clustered in operational taxonomic units. We observed high diversity of bacterial sediment communities as previously described by other studies. When we considered community composition, the most abundant classes were Alphaproteobacteria (27.7%), Acidimicrobiia (20%), Gammaproteobacteria (11.3%) and Deltaproteobacteria (6.6%). Most abundant OTUs at family level were from two uncultured bacteria from Actinomarinales (5.95%) and Kiloniellaceae (3.17%). The unexpected high abundance of Alphaproteobacteria and Acidimicrobiia in our deep-sea microbial communities may be related to the presence of asphalt seep at North São Paulo Plateau, since these bacterial classes contain bacteria that possess the capability of metabolizing hydrocarbon compounds.