Investigation of the putative iron reducing capabilities of Lokiarchaeota
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Marine subsurface sediments are large and ecologically significant microbial habitats. The archaeal phylum Lokiarchaeota is a group of organisms commonly found in these sediments. Their metabolism is unknown, but based on several indirect lines of evidence, it has been suggested that they are dissimilatory iron and/or manganese reducers, oxidising organic carbon using ferric iron [Fe(III)] and manganese [Mn(IV)] as electron acceptors. This study aims to further investigate these claims using a two-pronged approach: Firstly, to attempt to enrich Lokiarchaeota in vitro, and monitor the growth using molecular methods; secondly, to correlate Lokiarchaeota abundance data from quantitative polymerase chain reaction (qPCR) with data on iron and manganese concentration in the porewater of a long sediment core from the Arctic Mid-Ocean Ridge. The results of the study are largely inconclusive, but some evidence that support the hypothesis was found. 16S rRNA gene community profiles suggest that Lokiarchaeota might have grown in one of the enrichments containing amorphous Fe(III)-oxide and pyruvate, and a possible correlation between dissolved Fe(II) and Lokiarchaeota abundance was found in the sediment core.