Some types of extremophiles thrive in certain pH ranges.
An extremophile is any microbe that thrives in extreme conditions of temperature, pressure, salinity, or concentrations of hostile chemicals. Many extremophiles belong to the Archaea kingdom, also known as Archaebacteria, and most known Archaebacteria are extremophiles. Extremophiles also exist outside the Archaea kingdom; for example, there are eukaryotic bacteria and prokaryotes that are extremophiles, as well as worm, crustacean, and krill species.
The following are the different types of extremophiles. Some extremophiles may fall into more than one category:
Acidophilus: An organism with an ideal pH level of 3 or less. Alcaliphil: An organism with optimal growth at pH levels of 9 or above. Endolith: An organism that lives inside rocks. Halophile: An organism that requires at least 2M NaCl to grow. Hyperthermophile: An organism that can thrive in temperatures between 80-110 °C (176-230 °F). Hypolith: An organism that lives inside rocks in cold deserts. Metallotolerant: able to tolerate high levels of heavy metals such as copper, cadmium, arsenic and zinc. Oligotroph: An organism capable of growing in nutritionally limited environments. Piezophile: An organism that lives optimally under high hydrostatic pressure. Polyextremophile: An organism that can survive different extreme conditions. Psychrophile: An organism that can thrive in temperatures of 15 °C (59 °F) or less. Radioresistant: Resistant to high levels of ionizing radiation. Thermophile: An organism that can develop in temperatures between 60-80 °C (140-176 °F). Xerophile: An organism that can grow in environments with low water activity.
Archaebacteria are extremophiles.
The Pompeii worm, an extremophile, lives on the ocean floor clustered near hydrothermal vents. Living in temperatures of up to 176°F (80°C), these animals are the most heat tolerant known to science and are not even unicellular. Because they live in these isolated areas, many extremophiles were not discovered until the 1970s.
Perhaps the most memorable example of an extremophile is a bacterium, Streptococcus mitis, which was found embedded in the camera of the Surveyor 3 lunar probe by the Apollo 12 astronauts. This bacterium survived on the surface of the moon for three years. Scientists sometimes study extremophiles as potential models of what life might look like or how it might work on other worlds.