Bacterium: definition and meaning
BACTERIUMBacteria are single-celled organisms that are invisible to the naked eye and live alone or in colony and reproduce by simple division of their cells. They live in the most disparate environments and manage to overcome adverse conditions by transforming into spores.
In the biology of life they perform different and important functions: feeding on animal and plant remains carrying out an important cleaning and recycling action of organic matter; enter into symbiosis with other organisms and therefore have mutual benefit (eg the intestinal bacterial flora which helps digest the various substances ingested); to be parasites that is to live at the expense of other living organisms and therefore to be pathogenic bacteria that is, that cause diseases (eg the bacteria of leprosy, pneumonia, many plant bacteria, etc.).
Botanical dictionary from A to Z.