Bacteria display a large diversity of cell morphologies and arrangements.
The word bacillus (plural bacilli) may be used to describe any rod-shapedbacterium, and such bacilli are found in many different taxonomic groups of bacteria. However, the name Bacillus, capitalized and italicized, refers to a specific genus of bacteria. The name Bacilli, capitalized but not italicized, can also refer to a more specific taxonomic class of bacteria that includes two orders, one of which contains the genus Bacillus.
Bacilli are usually solitary, but can combine to form diplobacilli, streptobacilli, and palisades.