• (noun): (microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered plants.
    Synonyms: bacteria

Some articles on bacterium:

Lactobacillus L. Anticaries
... anticaries is a bacterium created by the German chemical company BASF ... This bacterium has been added to chewing gum, but it does not remove the need to brush your teeth ... The bacterium can be found in many varieties of yogurt ...