Böhnke, Stefanie, Hansen, C., Kleint, C., Klose, L., Adam-Beyer, Nicole, Sass, K., Dittmar, T., Koschinsky, A. and Perner, Mirjam (2022) Iron amendment to hydrothermal plumes induces shifts in microbial communities and provide first insights into the microbial organic iron-ligand production. [Poster] In: VAAM Jahrestagung 2022. , 20.-22.02.2022, virtuell .

Abstract

Iron is an essential micronutrient often limiting the growth of marine microorganisms in wide areas of the world’s
oceans. In high concentrations, iron, by contrast, is potentially toxic and usually leads to irreversible cell
encrustation followed by cell death. To counteract both, microorganisms have evolved the strategy of producing
organic iron-binding molecules, so called iron-ligands, enabling them to improve the bioavailability and uptake of
iron as well as to mitigate its potentially toxic effects. Hydrothermal vents are among the major sources of iron in
the oceans. These dynamic habitats host a variety of metabolically highly specialized and versatile microbes that not
only have to cope with partially high iron concentrations but may also be able to mediate the availability of
inorganic hydrothermal iron by actively producing iron-ligands.
However, hardly any information exists to-date describing the impact of increasing iron concentrations on
hydrothermal plume microbial communities and their potential to form iron-ligands. We therefore set up
microcosm experiments with hydrothermal plume material in artificial seawater along an iron gradient ranging from
0 to 10 mM. We found that the microbial community at low iron concentrations (0.1 to 100 μM) differs significantly
from that found in the original non-treated plume sample, allowing a certain group of Epsilonproteobacteria to
become dominant (up to 93% of the overall community). The microbial community detected at 10 mM is by
contrast more similar to that found in the original plume sample and consists mainly of one gammaproteobacterial
group (up to 97% of the overall community). We further analyzed these results in the context of ligand
concentrations and structural diversity and found indications for microbially mediated iron-ligand formation. This is
the first holistic experimental approach linking studies of hydrothermal vent microbial community composition with
the geochemistry involved in organic iron-ligand formation.

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