A bacillus (plural bacilli) is a rod-shaped bacterium. 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 less specific taxonomic group of bacteria that includes two orders, one of which contains the genus Bacillus. When the word is formatted with a lowercase and not italicized, 'bacillus', it will most likely be referring to shape and not to the genus at all. The shape bacillus can also be called rods.
- Diplobacilli: Two bacilli arranged side by side with each other.
- Streptobacilli: Bacilli arranged in chains.
- Coccobacillus: Oval and similar to coccus (circular shaped bacterium).
Examples of Gram positive bacilli
Examples of Gram negative bacilli
- Bacteroides genus
- Citrobacter genus
- Enterobacter genus
- Escherichia genus
- Pseudomonas genus
- Proteus genus
- Salmonella genus
- Serratia genus
- Shigella genus
- Yersinia genus
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