* Chemo: They obtain energy from chemical reactions, not sunlight.
* Litho: They use inorganic compounds.
Common inorganic compounds used by thermophiles:
* Hydrogen sulfide (H₂S): Used by many thermophiles living in hydrothermal vents.
* Elemental sulfur (S°): Another source in volcanic environments.
* Iron (Fe²⁺): Used by some thermophiles to oxidize ferrous iron to ferric iron.
* Hydrogen gas (H₂): Found in some volcanic settings.
Key examples:
* Sulphur-reducing bacteria: These thermophiles use sulfate (SO₄²⁻) as an electron acceptor and reduce it to hydrogen sulfide (H₂S). They are important in the sulfur cycle.
* Iron-oxidizing bacteria: These thermophiles oxidize ferrous iron (Fe²⁺) to ferric iron (Fe³⁺) to obtain energy. They play a role in the iron cycle.
In contrast to phototrophs:
* Phototrophs: Obtain energy from sunlight through photosynthesis (e.g., plants, algae).
* Chemotrophs: Obtain energy from chemical reactions.
Note: While most thermophiles are chemolithotrophs, some can also use organic compounds as an energy source (chemoorganotrophs).
Overall, the ability to use inorganic compounds for energy is a key adaptation that allows thermophiles to thrive in extreme environments with high temperatures and limited organic matter.
