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Abstract Denitrification accounts for a substantial nitrogen loss from environmental systems, shifting microbial composition and impacting other biogeochemical cycles. In Antarctica, rising temperatures cause increased organic matter deposition in marine sediments, which can significantly alter microbially mediated denitrification. To examine the genetic potential of microorganisms driving N-cycling in these sediments, benthic sediment cores were collected at two sites in the Weddell Sea, Antarctica. DNA was extracted from multiple depths at each site, resulting in the reconstruction of 75 high-quality metagenome-assembled genomes (MAGs). Forty-seven of these MAGs contained reductases involved in denitrification. MAGs belonging to the genus Methyloceanibacter were the most abundant MAGs at both sites and all depths, except depth 3–6 cmbsf at one site, where they were not identified. The abundance of these Methyloceanibacter MAGs suggests the potential for nitrate-driven methanol oxidation at both sites. MAGs belonging to Beggiatoaceae and Sedimenticolaceae were found to have the genetic potential to produce intermediates in denitrification and the complete pathway for dissimilatory nitrate reduction to ammonia. MAGs within Acidimicrobiia and Dadabacteria had the potential to complete the final denitrification step. Based on MAGs, Antarctic peninsula sediment communities have the potential for complete denitrification and dissimilatory nitrate reduction to ammonia via a consortium. 

Abstract The Antarctic sea urchin Sterechinus neumayeri (Echinoida; Echinidae) is routinely used as a model organism for Antarctic biology. Here, we present a high-quality genome of S. neumayeri. This chromosomal-level assembly was generated using PacBio long-read sequencing and Hi-C chromatin conformation capture sequencing. This 885.3-Mb assembly exhibits high contiguity with a scaffold length N50 of 36.7 Mb assembled into 20 chromosomal length scaffolds. These putative chromosomes exhibit a high degree of synteny compared to other sea urchin models. We used transcript evidence gene modeling combined with sequence homology to identify 21,638 gene models that capture 97.4% of BUSCO orthologs. Among these, we were able to identify and annotate conserved developmental gene regulatory network orthologs, positioning S. neumayeri as a tractable model for comparative studies on evolution and development.