Background
Hydrothermal vents along mid-ocean ridges host diverse microbial communities and are crucial to global elemental cycling. The Red Sea, known for its unique environmental conditions—including low nutrient levels, high year-round temperatures, bottom-water temperatures of 21 °C, and elevated salinity—hosts recently discovered active low-temperature hydrothermal vent fields at the axial Hatiba Mons volcano. These vents, characterized by large iron oxide mounds and abundant microbial mats, offer an extreme environment for studying the diversity and functions of prokaryotes involved in elemental cycling in this system. In this study, we used 16S rRNA sequencing and shotgun metagenomics to examine the microbial diversity and metabolic capabilities of precipitates and microbial mats from five vent sites.
Results
We recovered 314 non-redundant metagenome-assembled genomes (MAGs), including 250 bacterial and 64 archaeal MAGs, representing 34 bacterial and 11 archaeal phyla. Functional annotations revealed diverse nutrient and metal cycling potentials, with notable enrichment in iron redox genes. Key players include Bathyarchaeia and Chloroflexi in the precipitates (contributing to carbon, nitrogen, sulfur, and metal cycling potentials) and Pseudomonadota members in the microbial mats and upper precipitates (involved in iron and sulfur metabolism and carbon fixation through the Calvin–Benson–Bassham (CBB) cycle). Carbon fixation in precipitate communities primarily occurs through the Wood–Ljungdahl pathway. Sulfur and nitrogen cycling genes are distributed across various genomes, indicating collaborative cycling.
Conclusion
Our genome-resolved analysis positions the Hatiba Mons vents as an iron-rich system that provides new insights into oligotrophic hydrothermal environments, with potential relevance for understanding novel metabolic pathways, extremophilic adaptations, and their roles in element cycling and biotechnological applications.