Know how to use "fewer" and "less"? Find out.
1877, medical Latin, from Late Latin bacillus "wand," literally "little staff," diminutive of baculum "a stick," from PIE root *bak- "staff," also source of Greek bakterion (see bacteria). Introduced as a term in bacteriology 1853 by German botanist Ferdinand Cohn (1828-1898).
bacillus ba·cil·lus (bə-sĭl'əs)
n. pl. ba·cil·li (-sĭl'ī')
Any of various rod-shaped, usually gram-positive aerobic bacteria of the genus Bacillus that often occur in chains and include Bacillus anthracis, the causative agent of anthrax.
Any of various bacteria, especially a rod-shaped bacterium.
A genus of rod-shaped gram-positive bacteria capable of producing endospores.