CESIMAR - CENPAT   25625
CENTRO PARA EL ESTUDIO DE SISTEMAS MARINOS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Brown Algae Polysaccharide Assimilation Potential in Intertidal Sediments of a Subantarctic Sheltered Environment
Autor/es:
CALDEROLI PRISCILA ; DIONISI HEBE MÓNICA; LOZADA, MARIANA; GONZALEZ JESSICA ALEJANDRA
Lugar:
Atlanta
Reunión:
Congreso; ASM Microbe 2018; 2018
Institución organizadora:
American Society for Microbiology
Resumen:
Brown algae dominate high-latitude coastal environments. As polysaccharides constitute up to 50% of their dry weight, these biopolymers represent an important carbon source for sediment microbial communities. Alginates (1,4-linked β-D-mannuronate and α-L-guluronate) and fucoidans (fucose-containing sulfated polymers) are the two main matrix polysaccharides of their cell wall. We investigated the potential of microbial communities from intertidal sediments of Ushuaia Bay (Tierra del Fuego Island, Argentina) to assimilate these polysaccharides, in order to increase our understanding of the microbial populations that drive this important metabolic process of the carbon cycle, and the enzymatic mechanisms that they use. Sequences potentially coding for alginate- and fucoidan-depolymerizing enzymes were mined in a sequenced metagenomic library (0.7 Gb, N50 25 Kb), using dbCAN, pfam and custom-built HMMs. Putative alginate lyase and oligoalginate lyase sequences were very abundant in the dataset (1 every ~2,700 sequences). Sequences belonged to 6 of the 7 polysaccharide lyase (PL) CAZy families that include alginate depolymerizing enzymes. The scaffolds containing these sequences were assigned to 10 different phyla (PhylopythiaS), with Bacteroidetes (28.6%), Proteobacteria (24.9%) and Planctomycetes (17.4%) being the most abundant. Sequences of PL5 and PL14 families were most often found in scaffolds assigned to Planctomycetes, while those from the PL6, PL7, PL15 and PL17 families were most often identified in scaffolds assigned to Bacteroidetes. In agreement, correspondence analysis showed an association between certain PL families and the corresponding phyla, suggesting a differential contribution of guild members to the alginate depolymerizing gene pool. Putative fucoidanase sequences were less abundant (1 every ~97,600 sequences), although probably underestimated due to the lack of diversity of available sequences for HMM construction (GH107, 8 sequences from 4 bacterial strains). The identified metagenomic sequences shared low to medium identity values with members of the GH107 family (9-40% at protein level), and were often located in clusters that included putative alpha-L-fucosidase, sulfatase and acetyl esterase sequences, in particular those assigned to the Planctomycetes phylum (57% of the scaffolds). These results provide a community-wide profile of the potential for the degradation of key components of brown algae biomass, and constitute the foundation for their biotechnological application