Microbial community structure and cazyome of kelp-amended intertidal sediments

LOZADA, MARIANA; DIONISI, HEBE M.

Mendoza

Congreso; LVIII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2022

SAIB

Intertidal sediments host highly diverse microbial communities, mostly living in biofilms on the surface of the sediment particles. These microbial communities play key roles in the carbon cycle of coastal ecosystems, including the degradation of the beached kelp biomass. Approximately 50 % of the dry weight of kelp biomass are polysaccharides, mostly fucoidans and alginates. The goal of this work was to explore the CAZyome profile of metagenomes from intertidal sediment from two sites of the Patagonian coast amended with kelp biomass. Triplicate experimental systems were built containing sediments of Ushuaia Bay with blade fragments of the native kelp species Macrocystis pyrifera (M) or sediments of Nuevo Gulf with blade fragments of the exotic species Undaria pinnatifida (U), in sterile seawater. These kelp species are abundant at each site. Metataxonomic analyses (16S rRNA gene fragments) showed a rapid reduction in richness (~ 40 %) and diversity (~ 23 %) indices, when compared with experimental controls without kelp addition. The microbial community structure was enriched in members of the Proteobacteria, Bacteroidetes and Verrucomicrobia phyla. Two metagenomes were generated by shotgun sequencing from M and U amended sediments. The metagenomes (908,438 and 1,006,370 protein coding sequences for M and U metagenomes, respectively) were analyzed using the Conserved Unique Peptide Patterns (CUPP) tool, resulting in the identification of 23,517 (2.6 %) and 21,501 (2.1 %) sequences of putative CAZymes from the following classes: Auxiliary Activity (AA), Carbohydrate Esterase (CE), Glycoside Hydrolase (GH), Glycosyl Transferase (GT) and Polysaccharide Lyase (PL). Overall, 257 and 272 CAZy families were represented in M and U metagenomes, respectively. GH was the most abundant class in the metagenomes, with 43.21 % (M) and 48.41 % (U) of the sequences annotated into CAZy families. This class included 469 (M) and 453 (U) sequences assigned to families related to fucoidan degradation, mostly from the GH29, GH95, GH107 and GH168 families. The taxonomic assignment of these sequences showed that the majority probably originated in members of the Flavobacteriaceae family, although the PVC group (Planctomycetes, Verrucomicrobia and Kiritimatiellaeota phyla) was well represented in U-amended metagenomes. The PL class represented 6.16 % (M) and 5.50 % (U) of the annotated sequences, and included 13 of the 14 families containing alginate lyases (504 and 478 sequences for M and U, respectively). The sequences, mostly from the PL6, PL7 and PL17 families, were assigned to the Flavobacteriaceae, to Gammaproteobacteria and to the PVC and Terrabacteria groups. Overall, these results show the high diversity of enzymes encoded in the genome of bacteria with the potential to degrade fucoidans and/or alginates, and the taxa potentially involved in this process.