"These bacteria are truly unique, in the purest sense of the word," said lead author Li-Hung Lin, now at National Taiwan University, who performed many of the analyses as a doctoral student at Princeton and as a postdoctoral researcher at the Carnegie Institution's Geophysical Laboratory.
As Lin explained: "We know how isolated the bacteria have been because our analyses show that the water they live in is very old and hasn't been diluted by surface water. In addition, we found that the hydrocarbons in the local environment did not come from living organisms, as is usual, and that the source of the hydrogen (H2) needed for their respiration comes from the decomposition of water (H2O) by radioactive decay of uranium, thorium, and potassium."
Humans and most other land-dwelling organisms ultimately get their energy from the Sun, with photosynthetic plants forming the base of the food web. But in dark places where sunlight doesn't reach, life has to depend on other energy sources. Other communities of "chemoautotrophs"--a word chained together from Greek roots meaning "chemical self-nourishment"--have been found in exotic places such as aquifers, petroleum reservoirs, and vents linked to deep-sea volcanoes. Yet these communities all depend at least in part on nutrients that can be traced back to photosynthetic plants or bacteria.