An Electrochemical Study of the Influence ofMarinobacter aquaeoleion the Alteration of Hydrothermal Chalcopyrite (CuFeS₂) and Pyrite (FeS₂) under Circumneutral Conditions

Abstract

Pyrite and chalcopyrite are the two most abundant sulphides observed in seafloor hydrothermal systems. The alteration of sulphides is primarily controlled by reactions on the mineral surfaces and Fe(II)-oxidizing bacteria closely related to Marinobacter aquaeolei are thought to play a major role in iron oxidation under circumneutral conditions. We assessed the influence of M. aquaeolei on the electroactivity of FeS 2 and CuFeS 2 minerals under circumneutral conditions. Samples for the experiments were obtained from the Trans-Atlantic Geotraverse (TAG) hydrothermal mound (field), 26 • N on the Mid-Atlantic Ridge and Ireland (CuFeS 2 )]. The experimental approach relied on voltammetry and scanning electrochemical microscopy (SECM). The tip-substrate voltammetry mode of SECM was found to be particularly suitable to probe the major redox processes of those minerals and permitted an assessment of the microorganisms influence on these processes. M. aquaeolei was found to enhance FeS 2 and CuFeS 2 oxidation, particularly under suboxic conditions. M. aquaeolei also significantly enhances Fe dissolution under oxic circumneutral conditions but suppresses the dissolution of most other elements compared to abiotic conditions. Under abiotic conditions the surfaces of the minerals are rapidly passivated when oxygen is available; while addition of M. aquaeolei significantly hinders the passivation of chalcopyrite, no passivation of the pyrite surface is observed. This study demonstrates the ability of Marinobacter aquaeolei to enhance oxidation of FeS 2 and CuFeS 2 under circumneutral conditions and supports the involvement of Marinobacter species in weathering reactions on the seafloor and the control of the ultimate fate of sulphide deposits.

N2O formation by nitrite-induced (chemo)denitrification in coastal marine sediment

“…Several Marinobacter species have been found in Fe-rich habitats 55 , and their metabolic potential to utilize nitrate as terminal electron acceptors and iron (i.e. FeS 2 and CuFeS 2 ) as an electron donor has been demonstrated previously 40,56 . Potential Fe(III)-reducers (e.g.…”

Potential autotrophic carbon-fixer and Fe(II)-oxidizer Alcanivorax sp. MM125-6 isolated from Wocan hydrothermal field

“…Fe(II) oxidation and NaHCO 3 in the semi-solid medium act as energy source and sole carbon source for cell biosynthesis, respectively ( Emerson and Moyer, 2002 ; Emerson and Floyd, 2005 ). Many Fe(II)-oxidizing bacteria have been isolated and identified by gradient tubes, including but not limited to the chemoautotrophic Mariprofundus ferrooxydans genus (reviewed in reference McAllister et al, 2019 ), chemoheterotrophic Marinobacter ( Edwards et al, 2003b ; Smith et al, 2011 ; Müller et al, 2014 ; Leslie et al, 2015 ), and strains belonging to Hyphomonas jannaschiana ( Edwards et al, 2003b ). One strain (3B.1) affiliated to the Alcanivorax genus isolated from in situ enrichment igneous minerals and tested with gradient tubes was able to oxidize Fe(II) heterotrophically ( Smith et al, 2011 ).…”

Marinobacter: A case study in bioelectrochemical chassis evaluation

“…The ability of a number Marinobacter species to oxidize and reduce metals like iron and manganese (Bonis & Gralnick, 2015 ; Singer et al, 2011 ; Wang et al, 2012 ) and metalloids like arsenic and sulphur (Handley et al, 2009a , 2009b ; Rani et al, 2017b ) has been known for years, including their ability to oxidize solid minerals (Muller et al, 2014 ). This ability suggests that they could be electroactive as well, since organisms that are able to oxidize or reduce solid metals can often generate current on electrodes in BES.…”