Complete genome sequencing and comparison of two nitrogen- metabolizing bacteria isolated from Antarctic deep-sea sediment

Abstract Background: As global warming brings challenges, carbon neutralization, controlling CO2 emissions and the carbon peak are receiving increasing attention. The pelagic realm of the dark ocean represents a key site for the remineralization of organic matter, long-term carbon storage and carbon burial in the biosphere. In this paper, we explored the mechanisms of inorganic carbon fixation by deep-sea microorganisms at the genetic level.Results: In this paper, the basic genomic information of two strains was obtained by whole genome sequencing. The Cobetia amphilecti N-80 genome size is 4,160,095 bp, with a GC content of 62.5%. The Halomonas profundus 13 genome size is 5,251,450 bp, with a GC content of 54.84%. Through a comparison of the genomes and functional analyses, we predicted the C and N metabolic pathways of the two strains and determined that Halomonas profundus 13 can use more carbon sources than Cobetia amphilecti N-80. The main genes associated with N metabolism in Halomonas profundus 13 are narG, narY, narI, nirS, norB, norC, nosZ, and nirD. However, nirD, using NH4+ for energy, plays a main role in Cobetia amphilecti N-80. Cobetia amphilecti N-80 and Halomonas profundus 13 have the same genes for fixing inorganic carbon: icd, ppc, fdhA, accC, accB, accD, and accA.Conclusion: In this study, the whole genomes of two strains were sequenced to clarify the basic characteristics of their genomes, laying the foundation for further studying nitrogen-metabolizing bacteria. Halomonas profundus 13 can utilize more carbon sources than Cobetia amphilecti N-80, as indicated by API as well as COG and KEGG prediction results. Finally, through the analysis of the nitrification and denitrification abilities as well as the inorganic carbon fixation ability of the two strains, the related genes were identified, and the possible metabolic pathways were predicted. Together, these results provide molecular markers and theoretical support for the mechanisms of inorganic carbon fixation by deep-sea microorganisms.