Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.

Anaerobic oxidation of methane coupled to iron reduction (Fe-AOM) is a crucial process for methane removal in terrestrial environments. However, the occurrence of Fe-AOM in natural environments is rare, and the mechanisms behind the direct coupling of methane oxidation and iron reduction remain poor...

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Main Authors: Katsunori Yanagawa, Misaki Okabeppu, Sakiko Kikuchi, Fumito Shiraishi, Yumiko Nakajima, Akihiro Kano
Format: Article
Language:English
Published: Public Library of Science (PLoS) 2025-01-01
Series:PLoS ONE
Online Access:https://doi.org/10.1371/journal.pone.0319069
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author Katsunori Yanagawa
Misaki Okabeppu
Sakiko Kikuchi
Fumito Shiraishi
Yumiko Nakajima
Akihiro Kano
author_facet Katsunori Yanagawa
Misaki Okabeppu
Sakiko Kikuchi
Fumito Shiraishi
Yumiko Nakajima
Akihiro Kano
author_sort Katsunori Yanagawa
collection DOAJ
description Anaerobic oxidation of methane coupled to iron reduction (Fe-AOM) is a crucial process for methane removal in terrestrial environments. However, the occurrence of Fe-AOM in natural environments is rare, and the mechanisms behind the direct coupling of methane oxidation and iron reduction remain poorly understood. In this study, we investigated the environmental factors influencing the distribution of methanotrophic archaea in an iron-rich zone of a freshwater pond in Hiroshima Prefecture, Japan. High concentration of dissolved ferrous iron supplied by groundwater discharge led to considerable ferrihydrite precipitation. Pore water methane increased with sediment depth, while nitrate and sulfate concentrations were near detection limits throughout the sediment column. The coexistence of ferric iron and methane suggests the ongoing process of Fe-AOM. Tracer-based experiments using 14C showed potential Fe-AOM rates up to 110 pmol mL-1 day-1. Throughout the sediment core, except at the surface, PCR-based molecular ecological analyses of the 16S rRNA gene and functional genes for anaerobic oxidation of methane revealed abundant sequences belonging to the family "Candidatus Methanoperedenaceae". These geochemical and microbiological findings suggest that Fe-AOM plays a key role in biogeochemical cycles of iron and methane, positioning this environment as a modern analogue of early Earth conditions.
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spelling doaj-art-9c7d8a41bba248de84796d85c5e08f372025-08-20T01:51:27ZengPublic Library of Science (PLoS)PLoS ONE1932-62032025-01-01202e031906910.1371/journal.pone.0319069Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.Katsunori YanagawaMisaki OkabeppuSakiko KikuchiFumito ShiraishiYumiko NakajimaAkihiro KanoAnaerobic oxidation of methane coupled to iron reduction (Fe-AOM) is a crucial process for methane removal in terrestrial environments. However, the occurrence of Fe-AOM in natural environments is rare, and the mechanisms behind the direct coupling of methane oxidation and iron reduction remain poorly understood. In this study, we investigated the environmental factors influencing the distribution of methanotrophic archaea in an iron-rich zone of a freshwater pond in Hiroshima Prefecture, Japan. High concentration of dissolved ferrous iron supplied by groundwater discharge led to considerable ferrihydrite precipitation. Pore water methane increased with sediment depth, while nitrate and sulfate concentrations were near detection limits throughout the sediment column. The coexistence of ferric iron and methane suggests the ongoing process of Fe-AOM. Tracer-based experiments using 14C showed potential Fe-AOM rates up to 110 pmol mL-1 day-1. Throughout the sediment core, except at the surface, PCR-based molecular ecological analyses of the 16S rRNA gene and functional genes for anaerobic oxidation of methane revealed abundant sequences belonging to the family "Candidatus Methanoperedenaceae". These geochemical and microbiological findings suggest that Fe-AOM plays a key role in biogeochemical cycles of iron and methane, positioning this environment as a modern analogue of early Earth conditions.https://doi.org/10.1371/journal.pone.0319069
spellingShingle Katsunori Yanagawa
Misaki Okabeppu
Sakiko Kikuchi
Fumito Shiraishi
Yumiko Nakajima
Akihiro Kano
Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
PLoS ONE
title Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
title_full Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
title_fullStr Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
title_full_unstemmed Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
title_short Vertical distribution of methanotrophic archaea in an iron-rich groundwater discharge zone.
title_sort vertical distribution of methanotrophic archaea in an iron rich groundwater discharge zone
url https://doi.org/10.1371/journal.pone.0319069
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AT sakikokikuchi verticaldistributionofmethanotrophicarchaeainanironrichgroundwaterdischargezone
AT fumitoshiraishi verticaldistributionofmethanotrophicarchaeainanironrichgroundwaterdischargezone
AT yumikonakajima verticaldistributionofmethanotrophicarchaeainanironrichgroundwaterdischargezone
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