A study on microbial nitrogen cycling in coastal Antarctica reveals that the primary source of nitrate (NO₃⁻) is biological nitrification, with comammox Nitrospira clade B playing a key role as active nitrifiers. The research, based on isotopic analysis and metagenomic data, shows that the microbial nitrogen cycle in this region is distinct, excluding anaerobic ammonium oxidation. Comammox Nitrospira, capable of full nitrification, are well-adapted to cold and oligotrophic conditions, utilizing strategies such as trehalose synthesis and high substrate affinity. The study confirms the significant contribution of comammox Nitrospira to the nitrification process in coastal Antarctica, highlighting their importance in the nitrogen budget. The findings suggest that these bacteria are crucial for maintaining nitrogen cycling in this extreme environment, with potential implications for climate change. The research also provides insights into the microbial diversity and metabolic capabilities of Antarctic ecosystems, emphasizing the need for further investigation into the role of these microorganisms in global biogeochemical cycles. The study utilized a comprehensive dataset of over 450 gigabases of sequencing data to reconstruct 1968 metagenome-assembled genomes, revealing the genetic potential of various microbial groups involved in nitrogen cycling. The results underscore the importance of understanding microbial processes in extreme environments and their potential impact on global climate systems.A study on microbial nitrogen cycling in coastal Antarctica reveals that the primary source of nitrate (NO₃⁻) is biological nitrification, with comammox Nitrospira clade B playing a key role as active nitrifiers. The research, based on isotopic analysis and metagenomic data, shows that the microbial nitrogen cycle in this region is distinct, excluding anaerobic ammonium oxidation. Comammox Nitrospira, capable of full nitrification, are well-adapted to cold and oligotrophic conditions, utilizing strategies such as trehalose synthesis and high substrate affinity. The study confirms the significant contribution of comammox Nitrospira to the nitrification process in coastal Antarctica, highlighting their importance in the nitrogen budget. The findings suggest that these bacteria are crucial for maintaining nitrogen cycling in this extreme environment, with potential implications for climate change. The research also provides insights into the microbial diversity and metabolic capabilities of Antarctic ecosystems, emphasizing the need for further investigation into the role of these microorganisms in global biogeochemical cycles. The study utilized a comprehensive dataset of over 450 gigabases of sequencing data to reconstruct 1968 metagenome-assembled genomes, revealing the genetic potential of various microbial groups involved in nitrogen cycling. The results underscore the importance of understanding microbial processes in extreme environments and their potential impact on global climate systems.