Life from Molecules

Abstract

Living organisms are divided into three kingdoms, the eukaryotes , the eubacteria , and the archaebacteria . The eubacteria and the archaebacteria, which among themselves differ as much as they do from eukaryotes, are conventionally grouped together as prokaryotes . The bacteria common to most people, e.g., E. coli bacteria or the bacteria in sour milk , are eubacteria. Archaebacteria are typically found in rather hostile environments, such as in hot springs, at the bottom of deep sea, or in the very acidic milieu of the cow’s stomach. These bacteria do not tolerate oxygen and they often present a health hazard to humans. Eukaryotes are animals, plants, and fungi and include also single-cell organisms like yeast . Figure 1.1 gives examples of single cells from the three kingdoms.