EXPLAIN LIKE I'M 5

摘要

EXTREMOPHILES ARE WEE ORGANISMS THAT PERSIST IN conditions so harsh-so hot, so cold, so alkaline-that the creatures redefine our notion of what it takes to eke out a living. Biologist Thomas Brock first discovered these beings when he encountered the bacteria Thermus aquaticus in the boiling hot springs of Yellowstone Park in the 1960s. Ever since, micro-biologists have been searching the world's driest, hottest, deepest, and darkest spots to find creatures that flourish in conditions once thought uninhabitable. We've identified classes of microbes that thrive in incredibly high and low temperatures (thermophiles and psychrophiles), in shockingly acidic and basic pHs (acidophiles and alkaliphiles), and in crippling levels of pressure (barophiles) and salt (halophiles). There are even some that withstand two or more factors at once (polyextremophiles). These critters help explain how our first ancestors got their start 3.5 billion years ago, when our planet was remarkably hot. But they may also help us spot life beyond Earth: Astrobiolo-gists now know, for example, that organisms could theoretically exist below the surface of Titan, Saturn's largest moon. The orb's temperatures dip below -150 degrees Fahrenheit, and its underground ocean is as salty as the Dead Sea. But Earthly halo-psychrophiles (microbes tolerant of both cold and salt) prove that such conditions aren't necessarily as deadly as thev seem.