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Title: Aerobic and anaerobic iron oxidizers together drive denitrification and carbon cycling at marine iron-rich hydrothermal vents
Abstract

In principle, iron oxidation can fuel significant primary productivity and nutrient cycling in dark environments such as the deep sea. However, we have an extremely limited understanding of the ecology of iron-based ecosystems, and thus the linkages between iron oxidation, carbon cycling, and nitrate reduction. Here we investigate iron microbial mats from hydrothermal vents at Lōʻihi Seamount, Hawaiʻi, using genome-resolved metagenomics and metatranscriptomics to reconstruct potential microbial roles and interactions. Our results show that the aerobic iron-oxidizing Zetaproteobacteria are the primary producers, concentrated at the oxic mat surface. Their fixed carbon supports heterotrophs deeper in the mat, notably the second most abundant organism,Candidatus Ferristratumsp. (uncultivated gen. nov.) from the uncharacterized DTB120 phylum.Candidatus Ferristratumsp., described using nine high-quality metagenome-assembled genomes with similar distributions of genes, expressed nitrate reduction genesnarGHand the iron oxidation genecyc2in situ and in response to Fe(II) in a shipboard incubation, suggesting it is an anaerobic nitrate-reducing iron oxidizer.Candidatus Ferristratumsp. lacks a full denitrification pathway, relying on Zetaproteobacteria to remove intermediates like nitrite. Thus, at Lōʻihi, anaerobic iron oxidizers coexist with and are dependent on aerobic iron oxidizers. In total, our work shows how key community members work together to connect iron oxidation with carbon and nitrogen cycling, more » thus driving the biogeochemistry of exported fluids.

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Authors:
; ; ; ;
Award ID(s):
1833525 1155290
Publication Date:
NSF-PAR ID:
10206200
Journal Name:
The ISME Journal
Volume:
15
Issue:
5
Page Range or eLocation-ID:
p. 1271-1286
ISSN:
1751-7362
Publisher:
Nature Publishing Group
Sponsoring Org:
National Science Foundation
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