bacterium:  Bacterium was coined in the 1840s from Greek baktérion, a diminutive of báktron ‘stick’, on the basis that the originally discovered bacteria were rod-shaped. At first it was sometimes anglicized to bactery, but the Latin form has prevailed. Related, but a later introduction, is bacillus : this is a diminutive of Latin baculum ‘stick’, and the term was again inspired by the microorganism’s shape. Latin baculum is also responsible, via Italian bacchio and its diminutive form bacchetta, for the long French loaf, the baguette. => bacillus, baguette, débacle, imbecile
c. 1848, singular of bacteria (q.v.).
1. They found a bacterium visible to the human eye.
2. Treatment is supplemented with a course of antibiotics to kill the bacterium.
3. They have isolated the bacterium in its pure form.
4. A bacterium is identified as the cause for his duodenal ulcer.
5. Classification of the Haemophilus - like bacterium has been only tentatively determined.