Kwak, M.-J. | bioRxiv Science

bioRxiv2026

Who Formed All That Iron?: A Novel Antarctic Chemolithotroph Drives Iron Biomineralization

Iron mineralization has profoundly influenced Earths biogeochemical history1,2, yet the specific mechanisms underlying banded iron formation (BIF) remain unresolved3-5. Here we profile the microbiomes of Holocene sediments beneath the Larsen C Ice Shelf (LCIS), Antarctica6-8, through stratigraphic analysis of sedimentary ancient DNA combined with metagenomics. Distinct microbial phases aligned with glacial facies boundaries, with sub-ice shelf communities dominated by chemolithoautotrophs including an uncultured Thermodesulfovibrionia. This bacterium, visualized by fluorescence in situ hybridization and designated Candidatus Mariimomonas ferrooxydans (phylum Nitrospirota), emerged as a keystone taxon with high network centrality. Its genome encodes Cyc2, a fused porin-cytochrome outer membrane protein implicated in Fe(II) oxidation. Heterologous expression of Cyc2 in Escherichia coli confirmed its ability to catalyze iron oxidation, supporting iron precipitation under dark, anoxic conditions. These pristine LCIS sediments, unaltered since the last glacial maximum, provide a modern analogue for synglacial BIFs deposited during Neoproterozoic Snowball Earth events. Our findings deliver direct genomic and functional evidence for chemolithotrophic iron oxidation, challenge phototroph-centric models of BIF genesis, and highlight microbial iron cycling as a recurring force in Earths geochemical evolution. Beyond Earth, these insights inform interpretations of iron deposits on other planetary bodies.

microbiology↗

bioRxiv2023

Self-assembling Gn head ferritin nanoparticle vaccine provides full protection from lethal challenge of Dabie Bandavirus in aged ferrets

Dabie Bandavirus (DBV), previously known as Severe Fever with Thrombocytopenia Syndrome (SFTS) Virus, induces a characteristic thrombocytopenia with a mortality rate ranging from 12% to as high as 30%. The sero-prevalence of DBV in healthy people is not significantly different among age groups, but clinically diagnosed SFTS patients are older than [~]50 years, suggesting that age is the critical risk factor for SFTS morbidity and mortality. Accordingly, our immune-competent ferret model demonstrates an age (>4 years old)-dependent DBV infection and pathogenesis that fully recapitulates human clinical manifestation. To protect the aged population from DBV-induced SFTS, vaccine should carry robust immunogenicity with high safety profile. Previous studies have shown that glycoproteins Gn/Gc are the most effective antigens for inducing both neutralizing antibody (NAb)- and T cell-mediated immunity and, thereby, protection. Here, we report the development of a protein subunit vaccine with 24-mer self-assembling ferritin (FT) nanoparticle to present DBV Gn head region (GnH) for enhanced immunogenicity. Anion exchange chromatography and size exclusion chromatography readily purified the GnH-FT nanoparticles to homogeneity with structural integrity. Mice immunized with GnH-FT nanoparticles induced robust NAb response and T-cell immunity against DBV Gn. Furthermore, aged ferrets immunized with GnH-FT nanoparticles were fully protected from DBV challenge without SFTS symptoms such as body weight loss, thrombocytopenia, leukopenia, and fatality. This study demonstrates that DBV GnH-FT nanoparticles provide an efficient vaccine efficacy in mouse and aged ferret models and should be an outstanding vaccine candidate targeted for the aged population against fatal DBV infection. ImportanceDabie Bandavirus (DBV) is an emerging tick-borne virus that causes Severe Fever with Thrombocytopenia Syndrome (SFTS) in infected patients. Human SFTS symptoms progress from fever, fatigue, and muscle pain to the depletion of white blood cells and platelets with fatality rates up to 30%. The recent spread of its vector tick to over 20 states in the United States increases the potential for outbreaks of the SFTS beyond the East Asia. Thus, the development of vaccine to control this rapidly emerging virus is a high priority. In this study, we applied self-assembling ferritin (FT) nanoparticle to enhance the immunogenicity of viral Gn head domain as a vaccine target. Mice immunized with the GnH-FT nanoparticle vaccine induced potent antibody responses and cellular immunity. Immunized aged-ferrets were fully protected from the lethal challenge of DBV. Our study describes the GnH-FT nanoparticle vaccine candidate that provides protective immunity against the emerging DBV infection.

microbiology↗