The hyperthermophilic archaeon Pyrococcus furiosus utilizes environmental iron sulfide cluster complexes as an iron source

Reductive biomining of pyrite by methanogens

Pyrite (FeS₂) is the most abundant iron sulfide mineral in Earth's crust. Until recently, FeS₂ has been considered a sink for iron (Fe) and sulfur (S) at low temperature in the absence of oxygen or oxidative weathering, making these elements unavailable to biology. However, anaerobic methanogens can transfer electrons extracellularly to reduce FeS₂ via direct contact with the mineral. Reduction of FeS₂ occurs through a multistep process that generates aqueous sulfide (HS^-) and FeS₂-associated pyrrhotite (Fe_1-xS). Subsequent dissolution of Fe_1-xS provides Fe(II)_(aq), but not HS^-, that rapidly complexes with HS^-_(aq) generated from FeS₂ reduction to form soluble iron sulfur clusters [nFeS_(aq)]. Cells assimilate nFeS_(aq) to meet Fe/S nutritional demands by mobilizing and hyperaccumulating Fe and S from FeS₂. As such, reductive dissolution of FeS₂ by methanogens has important implications for element cycling in anoxic habitats, both today and in the geologic past.

A critical review of mineral-microbe interaction and coevolution: mechanisms and applications

The mineral-microbe interactions play important roles in environmental change, biogeochemical cycling of elements, and formation of ore deposits. Minerals provide both beneficial (physical and chemical protection, nutrients, and energy) and detrimental (toxic substances and oxidative pressure) effects to microbes, resulting in mineral-specific microbial colonization. Microbes impact dissolution, transformation, and precipitation of minerals through their activity, resulting in either genetically-controlled or metabolism-induced biomineralization. Through these interactions minerals and microbes coevolve through Earth history. The mineral-microbe interactions typically occur at microscopic scale but the effect is often manifested at global scale. Despite advances achieved through decades of research, major questions remain. Four areas are identified for future research: integrating mineral and microbial ecology, establishing mineral biosignatures, linking laboratory mechanistic investigation to field observation, and manipulating mineral-microbe interactions for the benefit of humankind.

Precipitation of greigite and pyrite induced by Thermococcales: an advantage to live in Fe- and S-rich environments?

Thermococcales, a major order of archaea inhabiting the iron- and sulfur-rich anaerobic parts of hydrothermal deep-sea vents, have been shown to rapidly produce abundant quantities of pyrite FeS₂ in iron-sulfur-rich fluids at 85°C, suggesting that they may contribute to the formation of 'low temperature' FeS₂ in their ecosystem. We show that this process operates in Thermococcus kodakarensis only when zero-valent sulfur is directly available as intracellular sulfur vesicles. Whether in the presence or absence of zero-valent sulfur, significant amounts of Fe₃ S₄ greigite nanocrystals are formed extracellularly. We also show that mineralization of iron sulfides induces massive cell mortality but that concomitantly with the formation of greigite and/or pyrite, a new generation of cells can grow. This phenomenon is observed for Fe concentrations of 5 mM but not higher suggesting that above a threshold in the iron pulse all cells are lysed. We hypothesize that iron sulfides precipitation on former cell materials might induce the release of nutrients in the mineralization medium further used by a fraction of surviving non-mineralized cells allowing production of new alive cells. This suggests that biologically induced mineralization of iron-sulfides could be part of a survival strategy employed by Thermococcales to cope with mineralizing high-temperature hydrothermal environments.