Iron reduction as a viable metabolic pathway in Enceladus' ocean

Recent studies postulated the viability of a suite of metabolic pathways in Enceladus' ocean motivated by the detection of H2 and CO2 in the plumes - evidence for available free energy for methanogenesis driven by hydrothermal activity at the moon's seafloor. However, these have not yet been explored in detail. Here, a range of experiments were performed to investigate whether microbial iron reduction could be a viable metabolic pathway in the ocean by iron-reducing bacteria such as Geobacter sulfurreducens. This study has three main outcomes: (i) the successful reduction of a number of crystalline Fe(III)-bearing minerals predicted to be present at Enceladus was shown to take place to differing extents using acetate as an electron donor; (ii) substantial bacterial growth in a simulated Enceladus ocean medium was demonstrated using acetate and H2(g) separately as electron donors; (iii) microbial iron reduction of ferrihydrite was shown to partially occur at pH 9, the currently accepted value for Enceladus' ocean, whilst being severely hindered at the ambient ocean temperature of 0 & DEG;. This study proposes the possibilities for biogeochemical iron cycling in Enceladus' ocean, suggesting that a strain of iron-reducing bacteria can effectively function under Enceladus-like conditions.

Automated summary

Recent studies have explored the metabolic pathways in Enceladus' ocean, suggesting the existence of methane generation driven by hydrothermal activity. This study investigates whether microbial iron reduction could occur in the ocean, and demonstrates the possibility of biogeochemical iron cycling in Enceladus' ocean.