Iron is one of the most important elements of the Earth, yet its bioavailability is limited in oceanic environments. In this context, deep-sea hydrothermal ecosystems represent one of the major sources of iron. While some microorganisms involved in its biogeochemical cycle, particularly in Fe(III)-reduction, have been isolated from these ecosystems, the molecular mechanisms underpinning metabolic pathways remain hypothetical and incomplete. Therefore, this study aims to investigate the global metabolism of bacteria within the Deferribacter genus, isolated from hydrothermal systems and a petroleum reservoir, with a specific focus on the Fe(III)-reduction metabolism to identify genes potentially involved in this pathway. This study revealed a conserved carbon metabolism across the four species, while their energetic metabolism exhibited notable differences. These species appear to be able to use different elements as electron sources, showing their ability to adapt to different ecological (micro)niches, particularly in deep-sea hydrothermal vents. The marker genes known for Fe(III)-reduction were identified, with a contrast between the strains isolated from hydrothermal systems and the one isolated from a petroleum reservoir. To further explore this pattern, the study was extended, including 14 genomes of representative strains and 36 metagenome-assembled genomes affiliated to the Deferribacterales order. Phylogenomic analysis revealed a distribution pattern within this order that correlates with environmental origin. Canonical marker genes of Fe(III)-reduction were also identified, with their distribution primarily aligned with specific ecological niches.
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