Resumo

Mangroves are widely distributed in tropical and subtropical regions around the world. They are coastal ecosystems with specific characteristics, positioned at the interface between terrestrial and marine environments. Located in floodplains, they show a wide variation in salinity and availability of oxygen. This combination of environmental conditions makes this environment rich in organic matter but poor in nutrients, due to the difficult decomposition of the organic compounds in the saline and prevalent anoxic conditions. In general, microbes living in mangroves have special adaptations to get nutrients in such harsh conditions, mainly by acting in the degradation of lignocellulosic biomass, by the action of extracellular enzymes. The xylanase is the enzyme responsible for transforming the hemicellulose in molecules that can be used to generate value-added products. Here, we assess the gene involved in the production of xylanase found in four mangroves areas (BrMgv01 to BrMgv04) by in silico analysis of metagenomic datasets (905.521 sequences), in combination with a functional screening of fosmidial clones that codify for this enzyme (searching in a metagenomic library with 12,960 clones). For functional screening we used the minimal medium supplemented with 0.2% xylan as the sole carbon source, and the enzyme activity was evidenced by the addition of a solution of iodine. The presence of clear zones around the colonies indicated production and secretion of xylanase, observed in three clones. The analysis in silico was accomplished through the server MG-Rast. For the abundance of the gene we used Subsystems database, revealing the occurrence of 363 reads for the BrMgv01, 181 for BrMgv02, 76 for BrMgv03, and 78 for BrMgv04. The reads found were compared with the GenBank database for the taxonomic affiliation of the sequences, revealing the dominance of the domain Bacteria, represented by the phyla Acidobacteria, Bacteroidetes, Firmicutes, Proteobacteria e Planctomycetes. These results show the existence of clones harboring xylanolytic activity in metagenomic libraries, and help us better understand possible transformations of organic matter in this environment. In so, it can be pointed the importance of exploring such environments from a biotechnology point of view.