Without the microbes in their complex, four-chambered stomachs, grazing animals like cows couldn't digest the tough cellulose fibers which are a major component of the grass they eat. The ability of microbes to thrive under extreme conditions is a legacy of their appearance early in Earth's history. It was this adaptability that enabled life to evolve in the primordial seas at a time when oxygen was scarce and the environment was hostile. When life began, the atmosphere consisted mainly of water vapour, hydrogen, hydrogen chloride, carbon monoxide and nitrogen. This biochemical process in turn paved the way for higher life forms which require oxygen for metabolism.
Microbes are so tough they can survive in outer space .
Modern space exploration and discovery has discovered that other worlds within our solar system and beyond support conditions which could harbour simple life forms. These could resemble the bacteria that flourished early in our planet's development and still exist in every ecosystem. It is highly possible even for certain bacteria to be transferred from one planet to another in comets and asteroids. With so much unknown about the origin and diversity of microbes, it is difficult to assess their importance to ecology and human life. They are certainly among the organisms most resilient to climatic change.