Job advert: postdoc position in Microbial Genomics of Extremophiles

The position (24 months) is open in the “Extremophiles” group led by Prof. Gaël Erauso in the Environmental Microbiology & Biotechnology team at the Mediterranean Institute of Oceanography (MIO) at Aix-Marseille University


A natural observatory for understanding the origins of life

The hydrothermal field of the Prony Bay (PHF, New Caledonia, South Pacific) comprises several intertidal and shallow submarine hyperalkaline springs located at less than 50 m below sea level (mbsl). Similarly to the deep-sea Lost City hydrothermal field (LCHF) located at ~800 mbsl, off the Mid-Atlantic Ridge (30°N), PHF relies on an serpentinizing basement and discharges into the seawater high pH (~11) fluids enriched in hydrogen (H2: 19–24% vol in free gas) and methane (CH4: 6–13% vol in free gas. When alkaline fluids mix with seawater, precipitation in the form of calcium carbonates (CaCO3), and brucite [Mg(OH)2] occurs, forming chimneys reaching up to tens of meters in height. Although PHF and LCHF display similar geochemical and mineralogical features, PHF is unique in that its hydrothermal features release low-temperature (< 40°C) and low-salinity fluids in a shallow submarine environment.

The search for the first colonizers of the primitive Earth

We are studying the main microbial trophic groups that are directly linked to the geochemistry of these ecosystems associated with serpentinization (production of hydrogen and methane in particular), to better understand the mechanisms of adaptation in extreme conditions (alkaline pH) and their role in hydrothermal chimney growing. We try to reproduce in the laboratory the conditions favorable to the development of native microorganisms. The enrichment and isolation of microorganisms using hydrogen or methane in the absence of oxygen is a major challenge for our team, as they could be the first colonizers of the primitive Earth.

18 years of scientific studies on the hydrothemal system of Prony by IRD

The extent of the Prony Bay hydrothermal field has been rediscovered and then re-studied since 2005 by IRD teams. Alkaline fluids form, in contact with seawater, several sites dominated bycarbonate chimneys that can reach several meters high. The emblematic example, a natural wonder, is the Aiguille de Prony, a privileged site known to scuba divers.

Alkaline fluids, hydrogen and methane: the basis for origin of life?

High amounts of hydrogen are emitted in the serpentinite-hosted hydrothermal field of the Prony Bay (PHF, New Caledonia), where alkaline, mesothermic and low-salinity fluids are discharged in both intertidal and shallow submarine environments.This original type of hydrothermalism had only been observed and considered in Lost City, discovered in 2000 at 800 meters below seawater near the Mid-Atlantic Ridge by American teams. At Prony, as at Lost City, the alkaline fluids are anoxic (poor in oxygen) and contain high quantities of hydrogen produced during the hydration of the rocks of the Earth’s mantle: an abiotic process called “serpentinization”. The hydrogen produced then reacts with surrounding carbon dioxide (carbon dioxide) to generate methane and other organic molecules such as alkanes, which can be used by microorganisms.

Alkaliphilus hydrothermalis

Several alkaliphilic bacteria have already been isolated from the Prony hydrothermal sources by the researchers of our MICROPRONY team. Among them, we note the isolation of the first alkalophilic bacterium associated with Prony hydrothermal field: Alkaliphilus hydrothermalis. Like most ecosystems studied on earth, most microorganisms detected on this site are still uncultivated, which bodes well for original discoveries to be made by microbiologists from the IRD and other French institutions working on this extreme ecosystem.

Gallery’s picture of sampling campaign 2022

This project is funded by the French National research Agency « ANR ». It is an interdisciplinary and international long-terme collaboration between researchers at the Mediterranean Institute of Oceanography, Geoscience Environnement Toulouse, Institut du Globe de Paris, Medis, Entropie, The Stony Brook University.