Padrões de diversidade microbiana em sedimentos marinhos profundos influenciados por uma exsudação de asfalto.

QUEIROZ, L. L. Microbial diversity patterns in deep-sea sediments influencied by asphalt seep. 2015. 59 p. Masters thesis (Microbiology) – Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, 2015. Deep-sea sediments are stable and homogeneous environments, however, they have a high variety of available habitats, allowing a high microbial diversity to occur. Microbial spatial distribution is determined by local and regional factors. Local factors are associated to environment structure and regional factors, to microbial dispersal limitation and historical events that may cause environmental changes. Historical events such as hydrocarbon emanation from sub-seafloor to seafloor may change the patterns of microbial spatial distribution, due to an increase of carbon, thus, selecting species capable to degrade them. These events are denominated as asphalt seep and they were found on the studied region. Considering the lack of knowledge and the importance of microorganisms on deep-sea sediments from South Atlantic ocean, this study aims to understand the patterns of microbial spatial distribution and how the oil from asphalt seep influence the microbial communities. This study was realized in São Paulo Plateau region. The plateau was divided in two regions, north and south. Microbial diversity was studied from 14 deep-sea sediment samples, nine samples from north region and five from south region. The asphalt seep was found in north region from São Paulo Plateau, directly affecting three of the nine samples. The communities were studied through denaturing gradient gel electrophoresis (DGGE), quantitative PCR (qPCR) and next generation sequencing (Ion Torrent). The spatial distribution of the communities was analyzed at different spatial scales: sediment depth ( 4 cm), local (1-34 Km) and regional (> 250 Km). Microbial communities were less similar between regions and showing relation with geographic distance to achaea and bacteria. Similarity values within regions were higher then between them, but the geographic distance was also important to both domains, despite samples being closer. Similarity values between sediment depths were high and have no relation with geographic distance. The cell number between sediment depths was different, with tendency to decrease with depth increase. The most abundant classes were Alphaproteobacteria (30%), Acidimicrobiia (18%), Gammaproteobacteria (16%), Deltaproteobacteria e Gemmatimonadetes (3%). The communities composition influenced by asphalt seep have no relation with oil presence and sediment depths. Geographic distance and asphalt seep were important factors to determine the spatial distribution of microbial communities in deep-sea sediments from São Paulo Plateau. Despite the absence of relation between oil from asphalt seep and communities composition, the high abundance of Alphaproteobacteria and the importance of distance within north region are indicative of heterogeneity increase caused by asphalt seep. More studies aiming to understand the geochemical composition from sediments and oil are necessary to explain how these factors influence the communities structure.