The Subduction Crew

WHAT IS AN EXTREMEOPHYLE?

by Homer Montgomery

What is an extremeophyle? Extremeophyles exist in unbelieveably difficult conditions. We could talk about various groups of extremeophyles, bacteria, eukaryotes, etc. I would like to (mostly) limit this discussion to eukaryotes. Extreme eukaryotic microbes are organisms that live in extreme environments. Studying these organisms is frequently not an easy task. Although these creatures are able to tolerate the most extreme conditions, they have proven quite difficult to study because they are so difficult to culture in the laboratory. As long as there is an energy source, eukaryotic microbial like is likely to be found. Below are categories within which to pigeon-hole extreme eukaryotic creatures.

Acidophiles - tolerate life at low pH. Four types of eukaryotes tolerate life at pH=0. At least one, Cyanidium, maintains its internal environment at pH=7. Many eukaryotes exist at slightly higher pH.
Alkalophiles - life at extremely high pH abounds. The African soda lakes with pH=10 support lots of microbes. You know something about this. These lakes are also responsible for making flamingoes pink. The key ingredient? Their diet is rich in alkalophiles, largely Spirulina.
Anaerobes - this category is yours. Find out all about anaerobes. Warning, this can be a smelly subject.
Barophiles - exist at extreme pressures. A good example for our purposes is the presence of sea cucumbers (an echinoderm) in the Challenger Deep, the deepest point in any ocean on earth.
Halophiles - tolerate high salt concentration. One organism, Dunaniella salina, is capable of surviving all the way up to salt saturation.
Psychrophiles - do cold better than any other organisms. The flagellate Heteromita is found on Antarctic sea ice at approximately –2° C. Laboratory attempts to cultivate Heteromita at even one degree above +2° C failed completely. One ciliate, Holosticha, was found to be unable to divide at temperatures above -2° C.
Thermophiles - tolerate extreme temperatures. A well-know example is Alvinella pompejana, the Pompeii worm. This worm lives on hydrotherm vents in water that averages 68° C, but which may exceed 81° C. You may have seen these polychaete worms on the PBS show Nova as life at a rift zone was explored.
Xerophiles - exist in the driest conditions. Lichens grow on rocks in deserts. The title of best colonizer of dry environments probably goes to fungi.

Your assignment:

Find examples of bacteria that qualify as extremeophyles. Find examples from the most extreme environments.

Communications | Humankind | Ecology | Geology