As humans, we enjoy fairly temperate and middle-of-the-road environmental conditions. Sure, we can hang out on a pretty hot summer day, or bundle up to brave the coldest winter evenings. But when considering the vast ranges of environmental conditions present on Earth, humans are quite limited by the environments in which they are able to survive. Many of the environments in which we find life thriving are unimaginable for human survival. One such environment is that of extreme pH, specifically, very basic or high pH environments (pH > 10). The organisms that thrive there are alkaliphiles.

Where would one even go to find an environment of high pH? The soda lakes in Africa are one example of a well-known environment with pH values greater than 9. The lakes are so alkaline that they could literally burn the skin right off most critters. One might guess that these waters might be devoid of fish, plants, or any life for that matter. Take a closer look, however, and one would find that the waters are teeming with life. So much that some species of birds actually feed on the organisms living there. Most famously are flamingoes, which get their pinkish color from the pinkish microorganisms they eat in the water. The life in soda lakes, as well as the animals feeding on this life, is specially adapted to survive highly basic conditions.

How does life survive there? Lets begin by examining a single cell in a highly basic solution. The way cells get energy to live is by coupling the synthesis of ATP, the energy currency of the cell, with proton transfer across cellular membranes. However, if there is an excess of hydroxyl (OH-) ions present inside or outside the cell membrane, this can disrupt the proton gradient needed to make ATP. Single celled alkaliphiles have special adaptations, such as negatively charged polymers within their cell membranes, which help combat the high concentrations of hydroxyl ions in the environment.

The extremes in which life on Earth is found thriving are unique and diverse. We can only imagine what the endpoints of the extremes for life might be like beyond Earth. It is certain, though, that we can extrapolate from what we have learned about life on Earth to make sense of the interesting environments beyond the blue marble we call home.

Works Cited:
Caviccioli, R. (2002). Extremophiles and the search for extraterrestrial life, Astrobiology, 2(3), 281-292.
Rothschild, L J., and Mancinelli, R L., (2001); Nature, vol. 409, 1092-1101.

Copyright © 2000-2008 Authors/Editors Chris Impey & Erika Offerdahl
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