Journal Article

Crystalline iron oxides stimulate methanogenic benzoate degradation in marine sediment-derived enrichment cultures

Yin, Xiuran, Wendt, Jenny, Elvert, Marcus, Kulkarni, Ajinkya C., Oni, Oluwatobi E., Harder, Tilmann, Kasten, Sabine, Friedrich, Michael W., Nimzyk, Rolf, Aromokeye, David A., Richter-Heitmann, Tim, Hinrichs, Kai-Uwe, Littmann, Sten, Tebben, Jan, Tienken, Daniela, Henkel, Susann

2021

Overview

Elevated dissolved iron concentrations in the methanic zone are typical geochemical signatures of rapidly accumulating marine sediments. These sediments are often characterized by co-burial of iron oxides with recalcitrant aromatic organic matter of terrigenous origin. Thus far, iron oxides are predicted to either impede organic matter degradation, aiding its preservation, or identified to enhance organic carbon oxidation via direct electron transfer. Here, we investigated the effect of various iron oxide phases with differing crystallinity (magnetite, hematite, and lepidocrocite) during microbial degradation of the aromatic model compound benzoate in methanic sediments. In slurry incubations with magnetite or hematite, concurrent iron reduction, and methanogenesis were stimulated during accelerated benzoate degradation with methanogenesis as the dominant electron sink. In contrast, with lepidocrocite, benzoate degradation, and methanogenesis were inhibited. These observations were reproducible in sediment-free enrichments, even after five successive transfers. Genes involved in the complete degradation of benzoate were identified in multiple metagenome assembled genomes. Four previously unknown benzoate degraders of the genera Thermincola (Peptococcaceae, Firmicutes) , Dethiobacter (Syntrophomonadaceae, Firmicutes), Deltaproteobacteria bacteria SG8_13 (Desulfosarcinaceae, Deltaproteobacteria), and Melioribacter (Melioribacteraceae, Chlorobi) were identified from the marine sediment-derived enrichments. Scanning electron microscopy (SEM) and catalyzed reporter deposition fluorescence in situ hybridization (CARD-FISH) images showed the ability of microorganisms to colonize and concurrently reduce magnetite likely stimulated by the observed methanogenic benzoate degradation. These findings explain the possible contribution of organoclastic reduction of iron oxides to the elevated dissolved Fe 2+ pool typically observed in methanic zones of rapidly accumulating coastal and continental margin sediments.

• Publisher: Nature Publishing Group UK,Oxford University Press
• Subject: 101/58 / 14/19 / 14/28 / 14/32 / 38/22 / 38/23 / 38/77 / 45/29 / 631/158/855 / 704/158/47 / Accumulation / Benzoates / Benzoic acid / Biodegradation / Biomedical and Life Sciences / Continental margins / Crystal structure / Crystallinity / Deltaproteobacteria / Ecology / Electron transfer / Enrichment / Evolutionary Biology / Ferric Compounds / Firmicutes / Fluorescence / Fluorescence in situ hybridization / Genomes / Geologic Sediments / Hematite / In Situ Hybridization, Fluorescence / Iron / Iron oxides / Life Sciences / Magnetite / Marine sediments / Methanogenesis / Microbial degradation / Microbial Ecology / Microbial Genetics and Genomics / Microbiology / Microorganisms / Organic carbon / Organic matter / Oxidation / Oxidation-Reduction / Oxides / Reduction / Scanning electron microscopy / Sediments / Slurries