Candidatus Desulforudis audaxviator is a species of bacterium that lives in groundwater at depths from 1.5–3 kilometres (0.93–1.86 mi) below the Earth's surface.

[1] Desulforudis audaxviator is the only bacterium found in water samples obtained 2.8 kilometres (1.7 mi) underground in the Mponeng Gold Mine in South Africa.

[2][3] Approximately four micrometres in length, it survives on chemical food sources derived from the radioactive decay of minerals in the surrounding rock.

A striking morphological feature of the organism is the presence of gas vesicles (provide cells the ability to flow in fluid enabling the CDA spores with this feature to spread to large distances), firstly distinguished from an early study of the closest relative of Desulforudis, Desulfotomaculum, which reported spores associated with gas vesicles and follow-up research showing that Desulfotomaculum spores could survive harsh temperature conditions and spread to the cold marine sediments.

The physiology that enables it to live in these extreme conditions is a tribute to its unusually large genome, consisting of 2157 genes instead of the 1500 of "streamlined" bacteria found in very stable environments.