Rhizosolenia mat diatoms associate with nitrogen-fixing microbes

Turk-Kubo, Kendra; Benavides, Mar; Mills, Matthew M; Smith, Sarah R

Rhizosolenia mat diatoms associate with nitrogen-fixing microbes

Turk-Kubo, Kendra ORCID: https://orcid.org/0000-0002-9847-7514; Benavides, Mar ORCID: https://orcid.org/0000-0001-9502-108X; Mills, Matthew M ORCID: https://orcid.org/0000-0002-9738-5589; Smith, Sarah R ORCID: https://orcid.org/0000-0003-1105-3127. 2025 Rhizosolenia mat diatoms associate with nitrogen-fixing microbes. ISME Communications, 5 (1). 10.1093/ismeco/ycaf159

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© The Author(s) 2025. Published by Oxford University Press on behalf of the International Society for Microbial Ecology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
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Official URL: https://doi.org/10.1093/ismeco%2Fycaf159

Abstract/Summary

Some Rhizosolenia diatoms living in oligotrophic marine ecosystems are known to form large, conspicuous mats and are thought to be sources of new nitrogen to surface waters via vertical migration to the nitracline where subsurface nitrate is accessed for growth. These vertically migrating Rhizosolenia mats are chronically under sampled, and both the diatom species comprising the mats and the associated microbiome have not been characterized using modern molecular techniques. Here we present the first DNA-based analysis of Rhizosolenia mats collected in the North Pacific Subtropical Gyre. Using sequencing of 18S rRNA and nifH genes (a proxy for N2 fixation capacity), we report on the molecular diversity of mat-forming Rhizosolenia species, which include two newly sequenced clades, and an assemblage of associated N2-fixing microorganisms that is distinct from the non-mat associated water column assemblage. Our findings advance knowledge of oligotrophic diatom diversity and challenge prevailing views of their nitrogen sources, suggesting these mats may obtain nitrogen through association-based N2 fixation. Further work is needed to understand the nature of these associations, and whether Rhizosolenia mat communities are a significant unrecognized source of N2-fixation-derived new nitrogen to the oligotrophic surface waters.

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1093/ismeco/ycaf159

ISSN:

2730-6151

Additional Keywords:

Rhizosolenia; diatoms; diazotrophs; N2 fixation; nifH

NORA Subject Terms:

Marine Sciences

Date made live:

29 Oct 2025 18:08 +0 (UTC)