First Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental Margins

Maxim Rubin-Blum,Beverly N Goodman-Tchernov,Rami Tsadok,Gilad Antler,James A Austin,Dan Tchernov,Zvi Ben-Avraham,Dwight F Coleman,Eli Shemesh,Wei-Chun Chin

doi:10.1371/journal.pone.0091456

Abstract

During the 2010–2011 E/V Nautilus exploration of the Levantine basin’s sediments at the depth of 300–1300 m, densely patched orange-yellow flocculent mats were observed at various locations along the continental margin of Israel. Cores from the mat and the control locations were collected by remotely operated vehicle system (ROV) operated by the E/V Nautilus team. Microscopic observation and phylogenetic analysis of microbial 16S and 23S rRNA gene sequences indicated the presence of zetaproteobacterial stalk forming Mariprofundus spp. – like prokaryotes in the mats. Bacterial tag-encoded FLX amplicon pyrosequencing determined that zetaproteobacterial populations were a dominant fraction of microbial community in the biofilm. We show for the first time that zetaproteobacterial may thrive at the continental margins, regardless of crustal iron supply, indicating significant fluxes of ferrous iron to the sediment-water interface. In light of this discovery, we discuss the potential bioavailability of sediment-water interface iron for organisms in the overlying water column.

Highlights

The recently described class of marine microbial iron oxidizers (FeOB), the zetaproteobacteria [1], is represented by a stalkforming prokaryote Mariprofundus ferrooxydans [2], prevails in the marine iron-oxidizing biofilms [1,3,4,5,6,7], and is mainly linked to hydrothermal activity [4,5,8] and exposed oceanic crust [9,10]
In this study we show that zetaproteobacterial mats are present throughout Israel’s continental margins, at depths of 300–1000 m and bring evidence showing that such mats are widespread along the Mediterranean continental margins
In this study we report the presence of patchy FeOB mats, abundant in the surveyed locations, unaffected by hydrothermal or hydrocarbon seepage, along the Levantine continental margin

Summary

Introduction

The recently described class of marine microbial iron oxidizers (FeOB), the zetaproteobacteria [1], is represented by a stalkforming prokaryote Mariprofundus ferrooxydans [2], prevails in the marine iron-oxidizing biofilms [1,3,4,5,6,7], and is mainly linked to hydrothermal activity [4,5,8] and exposed oceanic crust [9,10]. Since zetaproteobacteria studies are mostly limited to the deep sea, the iron-dependent carbon fixation is yet to be suggested as a considerable source of organic material in the benthic environment, and the effects of FeOB on benthic-pelagic iron exchange are yet unexplored. At sites of hydrothermal fluid emission and exposed ocean crust, high fluxes of ferrous iron from the crustal source provide metabolic energy to FeOB [4]. Significant benthic iron fluxes were recognized in the iron isotopic values measured within in situ benthic chambers, which emphasized the importance of the microbial iron reduction within sediment for the iron supply to the sediment surface and the water column [12]. Given significant benthic iron fluxes and oxygenated conditions at the sedimentwater interface, a niche for the FeOB can be formed at the continental margin, regardless of the crustal iron source

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Discussion

Conclusion