EXTREMOPHILES
INTRODUCTION
Earth hosts an array of varied environments which may range from hospitable to the most extreme environments where most life forms cannot survive or proliferate. However, there is a minority of organisms which have persisted and flourished in these extreme niches since life existed. The members of this minority, both single and multi-cellular, are collectively called extremophiles. Most known extremophiles are microbial in nature. The term 'Extremophiles' was termed by a biochemist Bob MacElroy who was associated with the Biological Adaptation Branch of NASA Ames where he studied Yellowstone thermophiles. He was working on the possibility of life in the Jupiter and Mars atmospheres. There are many reasons why extremophiles
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Many extremophiles are not exclusively classified in to one group because of their environmental niches. This is a common observation since extreme environments have a multitude of factors which are extreme. For instance, hydrothermal vents have extreme temperatures , may have extreme pH and pressures. The extremophiles, living here would fall under multiple classes. Such extremophiles are called polyextremophiles. The common categories of extremophiles are as follows:
Psychrophiles
Organisms with the ability to survive at temperatures below –4° F. Temperature plays havoc at extremely low temperatures. When water freezes and ice crystals are formed in the cell, the crystals and rupture the cells- killing it in the process.
They produce unique proteins that act as antifreeze agents and protect them against freezing. Some have layers encompassing the cell which does not harden upon freezing. Chryseobacterium greenlandensis, has survived since the past 120,000 years lives nearly two miles deep within the Greenland glacier ice.
Thermophiles
Organisms with the ability to survive at temperatures ranging from 140° F to