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Distribution in the marine environment

Iron is one of the main elements in the Earth’s crust . In the marine environment the most well-known class of iron oxidizing-bacteria is Zetaproteobacteria . These bacteria are generally microaerophiles, they adapted themselves to living in transition zones, where there is advective mixing of oxic and anoxic water. The Zetaproteobacteria are present in different Fe(II)-rich habitats. They are found in deep ocean sites associated with hydrothermal activity, but also in coastal and terrestrial habitats: they have been recovered from the surface of shallow sediments, beach aquifer, and surface water. Recently, it has also been studied their capacity to colonize steel surfaces, suggesting their role in corrosion processes . Mariprofundus ferrooxydans is one of the commonest and well-studied species of Zetaproteobacteria, it was first isolated from the Loihi seamount vent field, near Hawaii . At a depth of between 1100 and 1325 meters, on the summit of this shield volcano, vents can be found ranging from slightly above ambient (10°C) to high temperature (167°C). The vent waters are rich of CO₂, Fe(II) and Mn, but lack in H₂S . Around the vent orificies, can be found heavily encrusted large mats, and with a gelatinous texture, created by the FeOB as a byproduct of iron-oxyhydroxide precipitation. These areas can be colonized by other bacterial communities, but are also able to change the chemical composition and the flow of the local waters . There are two different types of vents at Loihi seamount: one with a focus and high temperature flow (above 50°C) and the other with a cooler (10-30°C) diffuse flow. The former creates mats of some centimetres near the orifices, the latter produces square meters mats 1m thick .