The microbial community structure and CAZyome of kelp-amended intertidal sediments

LOZADA, MARIANA; DIONISI, HEBE

Mendoza

Congreso; Congreso SAIB 2022; 2022

Intertidal sediments host highly diverse microbialcommunities, mostly living in biofilms on the surface of the sedimentparticles. These microbial communities play key roles in the carboncycle of coastal ecosystems, including the degradation of the beachedkelp biomass. Approximately 50 % of the dry weight of kelp biomassare polysaccharides, mostly fucoidans and alginates. The goal of thiswork was to explore the CAZyome profile of metagenomes fromintertidal sediment from two sites of the Patagonian coast amendedwith kelp biomass. Triplicate experimental systems were built,containing sediments of Ushuaia Bay with blade fragments of thenative kelp species Macrocystis pyrifera(M) or sediments of Nuevo Gulf with blade fragments of the exoticspecies Undaria pinnatifida(U), in sterile seawater. These kelp species are abundant at eachsite. Metataxonomic analyses (16S rRNA gene fragments) showed a rapidreduction in richness (~ 40 %) and diversity (~23 %) indices, whencompared with experimental controls without kelp addition. Themicrobial community structure was enriched in members of theProteobacteria, Bacteroidetes and Verrucomicrobia phyla. Twometagenomes were generated by shotgun sequencing from M and U amendedsediments. The metagenomes (908,438 and 1,006,370 protein codingsequences for M and U metagenomes, respectively) were analyzed usingthe Conserved Unique Peptide Patterns (CUPP) tool, resulting in theidentification of 23,517 (2.6 %) and 21,501 (2.1 %) sequences ofputative CAZymes from the following classes: Auxiliary Activity (AA),Carbohydrate Esterase (CE), Glycoside Hydrolase (GH), GlycosylTransferase (GT) and Polysaccharide Lyase (PL). Overall, 257 and 272CAZy families were represented in the M and U metagenomes,respectively. GH was the most abundant class in the metagenomes, with43.21 % (M) and 48.41 % (U) of the sequences annotated in the CAZyfamilies. This class included 469 (M) and 453 (U) sequences assignedto families related to fucoidan degradation, mostly from the GH29,GH95, GH107 and GH168 families. The taxonomic assignment of thesesequences showed that the majority probably originated in members ofthe Flavobacteriaceae family, although the PVC group (Planctomycetes,Verrucomicrobia and Kiritimatiellaeota phyla) was well represented inthe U-amended metagenomes. The PL class represented 6.16 % (M) and5.50 % (U) of the annotated sequences, and included 13 of the 14families containing alginate lyases (510 and 475 sequences for M andU, respectively). The sequences, mostly from the PL6, PL7 and PL17families, were assigned to the Flavobacteriaceae, toGammaproteobacteria and to the PVC and Terrabacteria groups. Overall,these results show the high diversity of enzymes encoded in thegenome of these organisms that could participate in the degradationof fucoidans and alginates, and the organisms potentially involved inthis process.p { margin-bottom: 0.25cm; direction: ltr; color: #000000; line-height: 115%; text-align: left; orphans: 2; widows: 2; background: transparent }p.western { font-family: "Calibri", serif; font-size: 11pt; so-language: es-AR }p.cjk { font-family: "Calibri"; font-size: 11pt; so-language: en-US }p.ctl { font-family: ; font-size: 11pt; so-language: ar-SA }