A sustained presence on Mars requires the production of food on site, but farming is limited by the local availability of suitable nutrients. Cyanobacteria can feed on Martian resources, and we hypothesized that the nutrients they mobilize could be extracted through anaerobic digestion and used as crop fertilizer. We therefore tested the abilities of three microbial communities to digest the biomass of Anabaena sp. in minimal medium, 200 g L^-1 Mars regolith simulant (MGS-1), and water. All communities produced ammonium and removed organic carbon in all media, especially in minimal medium and 200 g L^-1 MGS-1. However, MGS-1 also adsorbed organics and reduced the phosphate and ammonium recovery efficiency. A taxonomic analysis revealed a syntrophic fermentative community and hydrogenotrophic methanogens in minimal medium, but methanogens were outcompeted in MGS-1 by sulfate-reducing bacteria. Overall, this study suggests the viability of a bioprocess which could support crop production from Martian resources.

Microbial electrosynthesis has recently emerged as a promising technology for the sustainable production of organic acids, bioplastics, or biofuels from electricity and CO₂. However, the diversity of catalysts and metabolic pathways is limited to mainly mesophilic acetogens or methanogens. Here, eleven hyperthermophilic strains related to Archaeoglobales, Thermococcales, Aquificales, and methanogens were screened for microbial electrosynthesis. The strains were previously isolated from deep-sea hydrothermal vents, where a naturally occurring, spontaneous electrical current can serve as a source of energy for microbial metabolism. After 6 days of incubation in an electrochemical system, all strains showed current consumption, biofilm formation, and small organic molecule production relative to the control. Six selected strains were then incubated over a longer period of time. In the course of one month, a variety of metabolic intermediates of biotechnological relevance such as succinic acid and glycerol accumulated. The production rates and the promotion of specific metabolic pathways seemed to be influenced by the experimental conditions, such as the concentration of CO₂ in the gas phase and electron acceptor limitation. Further work is necessary to clearly identify these effects to potentially be able to tune the microbial electrosynthesis of compounds of interest.