Resumo

Although the mangrove ecosystems are essential for the existence of many species, they are continuously impacted by many pollutants that affect its stability. This environment is characterized as an anoxic region rich in organic matter, where sulfate acts as an important electron acceptor. It hosts a diverse and productive microbial community, which is directly related to nutrient cycling and degradation of organic matter and contaminants. In order to explore this community and the effect of contaminants on the structure, we evaluated the abundance by qPCR, the diversity by pyrosequencing and the networks by correlation analyses of Archaea, Bacteria, and Sulfate-reducing bacteria (SRB) communities in four mangroves under different stages of intervention [low content of oil contamination (BrMg01), 2 high content of oil contamination (BrMg02), 3 anthropogenic pollutants (BrMg03), 4 pristine (BrMg04)]. Higher abundances of Bacteria (log 10.4), Archaea (log 8.68) and SRB (log 5.27) were presented in BrMg02. Pyrosequencing revealed that in the domain Archaea, Euryarcheota (34-62%) and Crenarcheota (39-66%) were the most abundant phyla with no significant difference among the mangroves. In the Bacteria domain, the most abundant phyla were Proteobacteria (46-59%), Bacteriodetes (12-29%) and Acidobacterias (3-11%). Among the Proteobacteria, the dominance was observed for classes Deltaproteobacteria (48.2-65.6%) and Gammaproteobacteria (19.4-27.3%). Pyrosequencing of functional gene dsrB confirmed the dominance of Deltaproteobacteria class and Desulfobacteraceae family as the most frequent group of SRB in this niche. Network analyses showed that contamination simplifies the community structure by decreasing the interactions and the competition among microbial groups, possibly indicating the ability to use the contaminants as source of energy as the main characteristic to survive in the oil-polluted environment. Thus, the results of this study showed that the composition and interactions of microbial communities respond to the state of intervention of the mangroves, either based on taxonomical (ribosomal genes) or function-related genes(dsrB).