Extremophiles
Extremophiles are microbes that live in places you would not want to and are classified according to the environment they thrive in. Hence the first part of their name indicates the environment they reside in, the second part, “phile” means they thrive in it. It turns out there are many different environments, or to put it differently:
It is beyond the scope of this course to explore all the possible habitats of the extremophiles. If you are interested in these you can find a nice explanation for the different forms here. According to that site we have have:
Acidophile: An organism that grows best at acidic (low) pH values.
Alkaliphile: An organism that grows best at high pH values.
Anaerobe: An organism that can grow in the absence of oxygen.
Endolith: An organism that lives inside rock or in the pores between mineral grains. (Check out the video at right to learn about how research on endoliths done by one of our former Earth Sciences MSc. students might inform the search for life on other planets.)
Halophile: An organism requiring high concentrations of salt for growth.
Methanogen: An organism that produces methane from the reaction of hydrogen and carbon dioxide, a member of the Archaea.
Oligotroph: An organism with optimal growth in nutrient limited conditions.
Piezophile (Barophile): An organism that lives optimally at high hydrostatic pressure.
Psychrophile: An organism with optimal growth at temperature 15 °C or lower.
Thermophile: An organism with optimal growth at temperature 40 °C or higher.
Hyperthermophile: An organism with optimal growth at temperature 80 °C or higher.
Toxitolerant: An organism able to withstand high levels of damaging elements (e.g., pools of benzene, nuclear waste).
Xerophile: An organism capable of growth at very low water activity.
It will become obvious which of these extremophiles may be best suited for extraterrestrial life when we look some locations where we find them on Earth. There are a few localities that are well known prime examples of extremophile settings on earth, which we will visit next. We will cover everything you need to know for this course within this module, but if you are interested, you can read this a nice in-depth review article that covers extremophiles and the search for life within the solar system.
Let us now begin our own exploration of extremophiles. Our first set of extremophiles live in a deep dark place, devoid of sunlight.