Bacteria is the common name for a vast group of one celled microscopic organisms that encompasses the smallest, simplest, and perhaps first form of cell life that evolved. They constitute one of two divisions in the kingdom Monera. Bacteria furnish both the raw material and the chemical machinery for their own reproduction, whereas viruses, for example, do not. The oldest sign of life is a fossilized bacterial at about 3.5 billion years old.
The detail look on Bacteria as Microbe
