Structural Iron (II) of Basaltic Glass as an Energy Source for Zetaproteobacteria in an Abyssal Plain Environment, Off the Mid Atlantic Ridge

Abstract

To explore the capability of basaltic glass to support the growth of chemosynthetic microorganisms, complementary in situ and in vitro colonization experiments were performed. Microbial colonizers containing synthetic tholeitic basaltic glasses, either enriched in reduced or oxidized iron, were deployed off-axis from the Mid Atlantic Ridge on surface sediments of the abyssal plain (35°N; 29°W). In situ microbial colonization was assessed by sequencing of the 16S rRNA gene and basaltic glass alteration was characterized using Scanning Electron Microscopy, micro-X-ray Absorption Near Edge Structure at the Fe-K-edge and Raman microspectroscopy. The colonized surface of the reduced basaltic glass was covered by a rind of alteration made of iron-oxides trapped in a palagonite-like structure with thicknesses up to 150 μm. The relative abundance of the associated microbial community was dominated (39% of all reads) by a single operational taxonomic unit (OTU) that shared 92% identity with the iron-oxidizer Mariprofundus ferrooxydans PV-1. Conversely, the oxidized basaltic glass showed the absence of iron-oxides enriched surface deposits and correspondingly there was a lack of known iron-oxidizing bacteria in the inventoried diversity. In vitro, a similar reduced basaltic glass was incubated in artificial seawater with a pure culture of the iron-oxidizing M. ferrooxydans DIS-1 for 2 weeks, without any additional nutrients or minerals. Confocal Laser Scanning Microscopy revealed that the glass surface was covered by twisted stalks characteristic of this iron-oxidizing Zetaproteobacteria. This result supported findings of the in situ experiments indicating that the Fe(II) present in the basalt was the energy source for the growth of representatives of Zetaproteobacteria in both the abyssal plain and the in vitro experiment. In accordance, the surface alteration rind observed on the reduced basaltic glass incubated in situ could at least partly result from their activity.

Peeking under the Iron Curtain: Development of a Microcosm for Imaging the Colonization of Steel Surfaces by Mariprofundus sp. Strain DIS-1, an Oxygen-Tolerant Fe-Oxidizing Bacterium

“…The behavior of DIS-1 growing on the coupon surface is also reminiscent of stalk-forming FeOB that grow at hydrothermal vents and are related to DIS-1 (41). In this case, zetaproteobacteria also produce loosely adherent mats on the surfaces of basaltic lava substrata around the vents (11). This matrix of biogenic iron oxides can become colonized by other bacteria as well as be a substrate for continued auto-oxidation of Fe(II) and the adsorption of other minerals and elements, like silica and phosphorus.…”

Submarine Basaltic Glass Colonization by the Heterotrophic Fe(II)-Oxidizing and Siderophore-Producing Deep-Sea Bacterium Pseudomonas stutzeri VS-10: The Potential Role of Basalt in Enhancing Growth

“…They are thought to play an important role in redox transformations of Fe in deep-sea systems (Edwards et al, 2004), and they are commonly associated with diffuse seeps of Fe(II)-rich fluids (Emerson and Moyer, 2002; Edwards et al, 2011; Scott et al, 2015), as well as basaltic surfaces of varying age (Santelli et al, 2008; Sudek et al, 2009; Henri et al, 2016). …”

“…Reduced forms of elements such as Fe(II), Mn(II) and S(-II) in basalts can serve as potential electron donors for chemolithotrophic communities (Christie et al, 2001; Bach and Edwards, 2003; Henri et al, 2016). In addition, chemolithoautotrophic Fe(II)-oxidizing organisms are widely assumed to fix carbon that at least part of the basalt community relies upon (Santelli, 2007).…”

Prokaryote Communities at Active Chimney andIn SituColonization Devices After a Magmatic Degassing Event (37°N MAR, EMSO‐Azores Deep‐Sea Observatory)

“…Marne La Vallée, France), using the same synthesis protocol as previously described in Henri et al (2016). Marne La Vallée, France), using the same synthesis protocol as previously described in Henri et al (2016).…”

“…A few milligrams of synthetic basaltic glass substrates were inserted in each of them to act as microbial development substrate. The geomicrobiology colonization modules were prepared and deployed as described in Henri et al (2016) and will not be described into details.…”