Geobiology of the Extremophilic Archaeon Ignicoccus in Hydrothermal Systems – Implications for the Emergence of Life on Earth and Bey

Kurzfassung

Ignicoccus hospitalis is a hyperthermophilic chemolithoautotrophic archaeon inhabiting deepsea hydrothermal systems such as black smokers, which are considered candidate environments for the emergence of life on Earth and potential analogues for icy moon habitats [1]. Beyond adaptation to high temperatures (up to 98 °C), I. hospitalis shows high tolerance to ionising radiation, despite living in water depths of over 2000 m [2,3,4]. To further understand ecophysiological capabilities of extremophiles such as I. hospitalis and elucidate the habitability of hydrothermal systems for S0-reducing organisms more broadly, we investigated how metal concentrations characteristic of hydrothermal deep-sea systems affect microbial growth and survival. Our experiments involved anoxic cultivations of I. hospitalis, as well as microbial enrichments from different samples of hydrothermal origin. The microbial cultures were analysed using an integrated approach, including imaging techniques for observation of the cells (e.g. transmission electron microscopy) and detection of H2S to trace metabolic activity. We found that the metal tolerance of I. hospitalis follows the order: Mn (up to 100 mM) > Fe > Zn = Ni > Cu (up to 0.9 mM). Although no significant resistance to the tested metals was observed, a putative member of the genus Ignicoccus was successfully enriched from deep-sea hydrothermal sulfides sampled at the East Pacific Rise. This finding highlights the geobiological relevance of Ignicoccus for investigating Early Earth-like hydrothermal environments associated with the emergence of life, including black smokers that may also serve as analogues for potentially habitable icy moon environments. References [1] RUNGE et al. (2023) Geobiology 21 (3), 355-377. [2] PAPER et al. (2007) Int. J. Syst. Evol. Microbiol. 57, 803-808. [3] KOSCHNITZKI et al. (2021) Arch. Microbiol. 203 (4), 1299-1308. [4] LANGE (2009) Diploma Thesis, University of Regensburg.