Linking Zetaproteobacterial diversity and substratum type in iron-rich microbial mats from the Lucky Strike hydrothermal field(EMSO-Azores observatory)

Abstract

Zetaproteobacteria have been reported in differentmarine and terrestrial environments all over the globe. They play an essential role in marine iron-rich microbial mats, as one of their autotrophic primary producers, oxidizing Fe(II) and producing Fe-oxyhydroxides with differentmorphologies. Here, we study and compare the Zetaproteobacterial communities of iron-rich microbial mats from six differentsites of the Lucky Strike Hydrothermal Field through the use of the Zetaproteobacterial operational taxonomic unit (ZetaOTU) classification.We report for the firsttime the Zetaproteobacterial core microbiome of these iron-rich microbial mats, which is composed of four ZetaOTUs that are cosmopolitan and essential for the development of the mats. The study of the presence and abundance of differentZetaOTUs among sites reveals two clusters, which are related to the lithology and permeability of the substratum on which they develop. The Zetaproteobacterial communities of cluster 1 are characteristic of poorly permeable substrata, with little evidence of diffuseventing, while those of cluster 2 develop on hydrothermal slabs or deposits that allow the percolation and outflowof diffusehydrothermal fluids.In addition, two NewZetaOTUs 1 and 2 were identified,which could be characteristic of anthropic iron and unsedimented basalt, respectively. We also report significantcorrelations between the abundance of certain ZetaOTUs and that of iron oxide morphologies, indicating that their formation could be taxonomically and/or environmentally driven. We identifieda new morphology of Fe(III)-oxyhydroxides that we named "corals."Overall, our work contributes to the knowledge of the biogeography of this bacterial class by providing additional data from the Atlantic Ocean, a lesser-studied ocean in terms of Zetaproteobacterial diversity.