Bacteria are unicellular organisms.
Although some bacteria are the infectious agent in many human diseases, there are many strains that are harmless or even essential to humans. One important use of bacteria cultures is as producers of useful proteins. For example, a bacteria species called E. coli can be genetically altered so that it produces large amounts of human insulin, which can be administered to diabetics. The following is a brief overview of some of the characteristics of bacteria which make them ideal for many biotechnology applications. National Research Council Bacteria are prokaryote s, which means that they do not contain a cell nucleus.