185-1 Responses of Methanogens to Exogenous Metallophores with Dissolved and Mineral-Based Trace Metal Sources

Session: New Advances and Voices in Geobiology (Posters)

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Metallophores are biological molecules secreted by microorganisms or plants to acquire metals for various metabolic processes. They enhance metal bioavailability by forming complexes with dissolved metal ions for microbial uptake or promoting the dissolution of metal-bearing minerals. While many bacteria are known to produce their own or utilize external metallophores (“xenosiderophores”) to access trace metals from the surrounding environment, little is known about whether methanogens, among the oldest microbes on Earth and the earliest known nitrogen-fixing organisms, can similarly benefit from exogenous metallophores. Understanding such interactions is crucial for elucidating the interactions of methanogens with others in microbial communities and gaining insight into early microbial evolution.

Therefore, in this study, we examined the response of the model methanogen Methanosarcina acetivorans to two representative metallophores, catecholate protochelin and hydroxamate desferrioxamine B (DFOB), under varying trace metal sources. Our results demonstrated that M. acetivorans could not directly utilize metallophores or metal–metallophore complexes, as evidenced by reduced cell growth, methanogenesis, and nitrogen fixation efficiency when protochelin or DFOB were introduced. This is aligned with the absence of transport systems for metallophores or metal-metallophore complexes in M. acetivorans. However, although M. acetivorans was able to utilize metals from basalt and molybdenite for growth and metabolism, different cellular responses were observed when metallophores were introduced in the presence of these solid mineral sources. In basalt treatments, both metallophores no longer inhibited growth, likely due to enhanced mineral dissolution by metallophores with the release of free trace metals. In contrast, with molybdenite as the sole Mo source, high concentrations of metallophores still inhibited growth, while lower concentrations had minimal effect, potentially due to Fe limitation caused by metal-metallophore complexation. Transcriptomic analysis revealed upregulation of genes related to nitrogen fixation and methanogenesis in the presence of basalt or molybdenite. The addition of protochelin or DFOB altered the expression of genes related to metal transport and energy metabolism, correlating with observed shifts in growth and metabolic activities. These findings offer new insights into how methanogens acquire and utilize metals in complex environments, enhancing our understanding of early nitrogen fixation, microbial interactions, and the co-evolution of microbes and minerals.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7101

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