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Some Microbes Survive Massive Radiation!

by Jared Leadbetter

When most people think of "extreme environmental conditions", they tend to think of a wind chill factor in wintry St. Paul, Minnesota - or the summer heat in Phoenix, Arizona. But in the world of the microscopically small organisms, there are those who can survive what people might consider to be nothing less than death-defying conditions.

Some bacteria grow rather well in what could be described as battery acid, while others grow in a lake so salty that it is erroneously called the Dead Sea. Another group loves to grow in water so hot that it would boil over if it were not for the pressure cooker-like conditions at the bottom of the ocean. These same organisms consider room temperature to be as cold as the polar ice cap: they do not grow at all when temperatures dip down to those "icy cold" Phoenix summer extremes.

But perhaps one of the most unusual bacteria is one that is very highly resistant to what scientists had considered to be absolutely lethal radiation levels. Deinococcus radiodurans (said Din-o-coc-us rad-i-o-dew-ranz) is very remarkable for its ability to withstand radiation levels over 1000 times higher than that which would completely debilitate any human on earth. This organism was first found in food in the 1950's, food supposedly sterilized by radiation treatments.


Since that discovery, scientists have been studying Deinoccoccus in order to understand how it achieves this resistance. Currently, they are focusing on this organisms remarkable ability to repair major damage to its own DNA, which many consider to be the blueprint for life.

But scientists have also been trying to answer another question. Why is it that Deinococcus has evolved to be so radiation resistant, when radiation of such magnitude has only existed on earth during the last 50 years, a fraction of a second in evolutionary time. In the cases of the acid-, temperature- and salt-tolerant bacteria, their respective environments have existed at such extremes for millions of years.

Recently, it has been discovered that Deinococcus is as resistant to complete dehydration as it is to radiation. In fact, the same response is elicited by the organism when exposed to dry conditions as it is when exposed to high radiation levels, leading researchers to conclude that the organism evolved to survive long periods of dehydration, and that the resistance to radiation is only incidental to the discovery and development of radiation emitting technology during the second half of this century.

What new puzzles will microbes on earth present to us?


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