An extremophile is an organism that is able to live or even thrive in extreme environments, such as extreme temperature, pressure, radiation, salinity, or pH level. Extremophiles are mainly species of
The bright colors of Grand Prismatic Spring in Yellowstone National Park are produced by thermophiles, a type of extremophile.
Microscopic image from the hypersaline Lake Tyrrell (salinity> 20% w/v), in which the eukaryotic chlorophyte, Dunaliella salina, can be tentatively identified. Dunaliella salina is grown commercially for the carotenoid, β-carotene, which is widely used as a natural food colorant as well as a precursor to vitamin A. Alongside is the haloarchaeon, Haloquadratum walsbyi, which has flat square-shaped cells with gas vesicles that allow flotation to the surface, most likely to acquire oxygen.