A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the

sense A sense is a biological system used by an organism for sensation, the process of gathering information about the world through the detection of stimuli. (For example, in the human body, the brain which is part of the central nervous system rec ...

clear), is a rod-shaped

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were a ...

or archaeon. 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 lowercase and not italicized, 'bacillus', it will most likely be referring to shape and not to the genus at all. Bacilliform bacteria are also often simply called rods when the bacteriologic context is clear. Bacilli usually divide in the same plane and are solitary, but can combine to form diplobacilli, streptobacilli, and palisades. * Diplobacilli: Two bacilli arranged side by side with each other. * Streptobacilli: Bacilli arranged in chains. * Coccobacillus: Oval and similar to coccus (circular shaped bacterium). There is no connection between the shape of a bacterium and its color upon Gram staining; there are both gram-positive rods and gram-negative rods. MacConkey agar can be used to distinguish among gram-negative bacilli such as '' E. coli'' and salmonella.

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...
examples

* '' Actinomyces'' * '' Bacillus'' * '' Clostridium'' * '' Corynebacterium'' * '' Listeria'' * '' Propionibacterium''

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
examples

* '' Bacteroides'' * '' Citrobacter'' * '' Enterobacter'' * '' Escherichia'' * '' Klebsiella'' * '' Pseudomonas'' * ''

Proteus In Greek mythology, Proteus (; Ancient Greek: Πρωτεύς, ''Prōteus'') is an early prophetic sea-god or god of rivers and oceanic bodies of water, one of several deities whom Homer calls the " Old Man of the Sea" ''(hálios gérôn)''. ...

'' * '' Salmonella'' * '' Serratia'' * '' Shigella'' * '' Vibrio'' * '' Yersinia'' {{Bacteria Bacteria

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ... examples

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ... examples

Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bac ...
examples

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...
examples