Figure 5.

Schematic of potential carbon and microbe relationship in the Lost City chimneys, adapted from [14]. Since ΣCO₂ is extremely scarce in the fluids of alkaline serpentinization systems, the growth of chemolithoautotrophic organisms may require the presence of a heterotrophic foundation species that supplies bioaccessible inorganic carbon to the community. We hypothesize that at the Lost City sulfate reducers convert abiotic formate into CO₂ that is then used by species such as the Lost City Methanosarcinales to carry out hydrogenotrophic methanogenesis. (Online version in colour.)