Syntrophic Effects in a Subsurface Clostridial Consortium on Fe(III)-(Oxyhydr)oxide Reduction and Secondary Mineralization

Abstract

In this study, we cultivated from subsurface sediments an anaerobic clostridial consortium that was composed of a fermentative Fe-reducer Clostridium species (designated as strain FGH) and a novel sulfate-reducing bacterium belonging to the clostridia family Vellionellaceae (designated as strain RU4). In pure culture, Clostridium sp. strain FGH mediated the reductive dissolution/transformation of iron oxides during growth on peptone. When Clostridium sp. FGH was grown with strain RU4 on peptone, the rates of iron oxide reduction were significantly higher. Iron reduction by the consortium was mediated by multiple mechanisms, including biotic reduction by Clostridium sp. FGH and biotic/abiotic reactions involving biogenic sulfide formed by strain RU4. The Clostridium sp. FGH produced hydrogen during fermentation, and the presence of hydrogen inhibited growth and iron reduction activity. The sulfate-reducing partner strain RU4 was stimulated by the presence of H 2 and generated reactive sulfide which promoted the chemical reduction of the iron oxides. Characterization of Fe(II) mineral products showed the formation of nanoparticulate magnetite during ferrihydrite reduction, and the precipitation of iron sulfides during goethite and hematite reduction. The results suggest an important pathway for iron reduction and secondary mineralization by fermentative sulfate-reducing microbial consortia through syntrophy-driven biotic/abiotic reactions with biogenic sulfide.

High spatial resolution of distribution and interconnections between Fe‐ and N‐redox processes in profundal lake sediments

“…Interestingly, although poorly crystalline iron is generally considered to be more bioavailable, both the poorly crystalline and highly crystalline fractions vary with depth. This indicates that redox transformations between its oxidized and reduced form occur in both crystallinity fractions, as has been observed before (Wu et al ., ; Muehe et al ., ; Shah et al ., ).…”

Impact of iron reduction on the metabolism of Clostridium acetobutylicum

“…S2). Studies of fermentative solid iron reduction by Grampositive organisms related to C. acetobutylicum showed efficient iron reduction rates, but they grew in the presence of an electron shuttle, natural groundwater or sediments (the latter two can contain natural exogenous electron shuttles) (Lehours et al, 2010;Shah et al, 2014;Dong et al, 2016Dong et al, , 2017. Thus, while solid iron reduction by C. acetobutylicum is slow in a laboratory setting, soils and sediments are expected to harbour electron shuttles (e.g., humic substances), which may be used by the organisms to transfer electrons to iron oxides.…”

Hydrologic Alteration and Enhanced Microbial Reductive Dissolution of Fe(III) (hydr)oxides Under Flow Conditions in Fe(III)-Rich Rocks: Contribution to Cave-Forming Processes

“…In these cultures we saw a shift in microbial community structure from the Proteobacteria-dominated sub muros to one dominated by the Firmicutes, representing >97% of sequences (Figure 2). In these previous experiments, we had assumed that the shift in community structure had been driven in part by the high amount of organic carbon, while the closed nature of the experiment allowed H 2 to accumulate and drive fermentative Fe-reduction by members of the Clostridia (Shah et al, 2014;Parker et al, 2018). We tested this hypothesis in this study, using a basal medium (SPW) and 5 mM lactate as a carbon source.…”