Classification of Yersinia enterocolitica: is done most commonly by 16S rDNA (ribosomal DNA) sequence analysis.


Domain: Bacteria

Kingdom: Bacteria

Phylum: Proteobacteria

Class: Gamma Proteobacteria

Order: "Enterobacteriales"

Family: Enterobacteriaceae

Genus: Yersinia

Species: Yersinia enterocolitica

A phylogenetic tree of living things, based on rRNA data, showing the separation of bacteria, archaea, and eukaryotes

Image courtesy of Samsara

English Definition:

Yersinia: named after Alexandre Émile Jean Yersin: A Swiss born French Bacteriologist (1863-1943)
Enterocolitica: pertaining to the intestine and colon. Enterics: refers to the gut. Colon: of the colon. Iticos: pertaining to.


Domain and Kingdom: Bacteria: Yersinia enterocolitica is classified as Bacteria or Eubacteria because it contains peptidoglycan within the cell walls as well as lacks internal organelles. Cell walls are found in plant cells, some protists, and fungi, as well as prokaryotic cells. In Bacteria, the cell wall is used for protection as well as support. One major difference in the cell walls of bacteria is the presence of peptidoglycan. Peptidoglycan provides the foundations for bacterial cell walls. It also allows for gram staining. What is gram staining you ask? Well gram staining is a staining technique used to determine if an individual bacterium is gram-negative or gram-positive. Gram-negative bacteria exhibit a pinkish red color after dyed where as gram-positive bacteria exhibit a purple color. Below are comparisons of a gram negative stain and a gram positive stain. Can you tell which is which?

Magnified 956X, this Gram-stained photomicrograph depicted numbers of the Gram-positive Clostridium innocuum bacteria A photomicrograph of Yersinia enterocolitica using gram stain technique. (gram negative)

Images courtesy of

The difference in color stems from the location of the peptidoglycan within the cells walls. Crazy right? Peptidoglycan is the outermost layer in gram-positive cell walls whereas gram-negative cells exhibit an outer membrane beyond that of the peptidoglycan layer. Riveting stuff, I know. Further explanation can be found in the image below.

Gram negative vs. Gram positive

Image courtesy of Graevemoore


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Phylum: Proteobacteria: Proteobacteria was once referred to as Purple bacteria (phototrophic bacteria that are purple in color and carry out a unique form of photosynthesis using a specialized pigment) and their relatives but because of their wide range of shape and physiology Proteobacteria was suggested as the name to unite the group. Yersinia enterocolitica would have been grouped in the 'and their relatives' stipulation. The reason Proteobacteria was chosen as the name is that Proteus was a Greek god of the sea, capable of assuming many different shapes. Fitting that despite a common ancestor, the Proteobacteria have a diverse range of properties. I hope these bacteria realize their Greek god relation, as it is quite the compliment. Yersinia enterocolitica is classified as a proteobacteria because it contains specific signature nucleotides based on a 16s RNA sequence (Stackebrandt, et al 1988).
Class: Gamma Proteobacteria: According to Bergey's Manual of Determinative Bacteriology the class gamma proteobacteria is defined as a class of bacteria having 16S rRNA gene sequences related to those of the members of the order Pseudomonadales. Yersinia enterocolitica has a 16S rRNA gene sequence related to the order Pseudomonadales.

Phylogenetic tree derived from Fig. 1. in Was our ancestor a hyperthermophilic procaryote?

Phylogenetic tree derived from Fig. 1. in Was our ancestor a hyperthermophilic procaryote?


Another organism within the Gamma Proteobacteria that also causes diarrhea is Vibrio cholerae. (To learn more about Vibrio cholerae click here!)


Order: “Enterobacteriales”: Enterobacterium meaning an intestinal bacterium. Only one family within this order being Enterobacteriaceae and Yersinia enterobacteria is itself an intestinal bacterium fitting it within the "Enterobacteriales".
Family: Enterobacteriaceae: These are gram-negative, rod shaped bacteria that are facultatively anaerobic in nature meaning they can perform aerobic respiration when oxygen is present but have the ability to switch to fermentation in a system when oxygen is lacking. This is in contrast to obligate anaerobic respiration organisms which die in the presence of oxygen. Enterobacteriaceae are also lacking in cytochrome oxidase and therefore are referred to as oxidase negative. This meaning that they do not use oxygen as the final electron acceptor in the Electron Transport Chain. Also, within Enterobacteriaceae, organisms are either lactose-positive or lactose-negative meaning that they either produce or lack lactase. Yersinia enterocolitica is lactose-negative along with Salmonella enteritidis (to learn more about Salmonella enteritidis click here!) whereas Escherichia coli is lactose positive. (To learn more about Esherichia coli click here!)  


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Genus: Yersinia: the virulent strains that are pathogenic to humans all carry a 70 kb virulence plasmid (pYV) on a high pathogenicity island (HPI) which also carries yersiniabactin (Garzetti, et al 2012). Plasmids are small circular pieces of double stranded DNA that replicate autonomously. To learn more about plasmids and reproduction click here. While the non-virulent strains in the genus have lost these all virulent strains contain them. They use this to overcome host immune defense and to infect the lymph tissues. All species within the genus are motile from 22-29 degrees Celsius except Yersinia pestis. (To learn more about Yersinia pestis click here!) These species are motile via peritrichous flagella which are diagramed below.


Example of peritrichous flagella (surrouding the cell)

Image created by Skyler Hying

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Species:Yersinia enterocolitica: This is the scientific name for this specific organism. This name is based off the binomial system of nomenclature. This system uses a two part name that is of Latin based grammatical form. The first of which is the genus name, the second is the species name within the genus.



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