Until now, these bacteria were only known to grow in low-oxygen environments, but genetic sequences have also been detected on occasion in hydrothermal plumes.

New research has shown that certain bacteria live in the depths of the oceanat the limits of the tectonic plates, where hot fluids arise from the so-called hydrothermal vents, which lack oxygen and contain large amounts of metals such as iron, manganese or copper, and even sulphides, methane and hydrogen.

When hot water mixes with intermittently cold, oxygenated seawater, so-called hydrothermal plumes are formed, which contain smoke-like metal sulfide particles. These plumes rise hundreds of meters from the seafloor and disperse thousands of kilometers from their source. Hydrothermal plumes can seem like a precarious place to feel at home, but this does not prevent certain bacteria from flourishing right thereaccording to the study, published in the journal ‘Nature Microbiology’.

«We analyzed in detail the bacteria of the genus Sulfurimonas,» explains first author Massimiliano Molari, from the Max Planck Institute for Marine Microbiology in Bremen, Germany. «Until now these bacteria were only known to grow in low-oxygen environments, but genetic sequences were also occasionally detected in hydrothermal plumes. As the name suggests, is known to use the energy of sulfur«, remember.

«It was assumed that they were washed up there from environments associated with seafloor ventsbut we wonder if the feathers might actually be a suitable environment for some members of the Sulfurimonas group.»


Together with colleagues from the Alfred Wegener Institute, the Helmholtz Center for Polar and Marine Research Bremerhaven (AWI) and the MARUM Center for Marine Environmental Sciences at the University of Bremen, Molari thus undertook a difficult journey of proven to hydrothermal plumes of the Central Arctic and the South Atlantic Ocean.

«We took feather samples in extremely remote areas of ultra-slow spreading ridges that had never been studied before. Collecting samples of hydrothermal plumes is very easy, since they are not easy to locate. The demonstrated one becomes even more difficult when the plume is more than 2,500 meters deep and under the sea ice of the Arctic, or within the stormy areas of the Southern Ocean,» explains Antje Boetius, group leader at the Max Planck Institute for Marine Microbiology and director of the AWI, who was the chief scientist for the missions in the Arctic.

TO aboard the research vessel PolarsternThe scientists managed to collect samples and, within this water, they studied the composition and metabolism of the bacteria.

Molari and colleagues identified a new species of Sulfurimonas called ‘USulfurimonas pluma’ (superscript «U» stands for uncultivated) that inhabits cold, oxygen-saturated hydrothermal plumes. Surprisingly, this microorganism used hydrogen from the plume as its energy source, instead of sulfur.

Connection with the seabed

The scientists also investigated the genome of the microbes and found that it was greatly reduced, lacking genes typical of its relatives, but well equipped with others that allowed it to thrive in this dynamic environment.

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«We think that the hydrothermal plume not only disperses microorganisms from hydrothermal vents, but also the open ocean could be ecologically connected to seafloor habitats. Our phylogenetic analysis suggests that USulfurimonas pluma might have derived from a hydrothermal vent-associated ancestor, which acquired increased oxygen tolerance and then dispersed across the oceans. However, much remains to be investigated,» says Molari.

An examination of genomic data from other feathers reveals that USulfurimonas feather grows in these environments throughout the world. «Obviously, they’ve found an ecological niche in the cold, oxygen-saturated, hydrogen-rich hydrothermal plumes,» Molari said. «That means we have to rethink our ideas on the ecological role of Sulfurimonas in the deep ocean: they could be much more important than we thought.»