Bacteria are the oldest, structurally simplest, and most abundant forms of life on earth.
They play a vital role both in productivity and in cycling the substances essential to all other life forms. There are about 4800 different kinds of bacteria currently recognized, but there are doubtless many thousands more awaiting identification. Kingdom Eubacteria Eubacteria are distributed more widely than any other group of organisms, such as a single gram of soil my contain over a billion bacteria. The following examples are all from the Phylum Cyanobacteria, and share some distinct characteristics.