Microscopic view of Shigella sonnei (Public Domain)

ClassificationShigella being tested (Permission Granted)

 

Domain: Bacteria
Kingdom: Eubacteria
Phylum: Proteobacteria
Class: Gamma proteobacteria
Order: Enterobacteriales
Family: Enterobacteriaceae
Genus: Shigella
Species: Shigella sonnei 

                                  

Shigella sonnei is named after the Danish bacteriologist Carl Olaf Sonne. The genus Shigella was named after Kiyoshi Shiga who first discovered it in 1898.

Domain and Kingdom
Shigella sonnei fits into the Domain and Kingdom Bacteria (Eubacteria) because members of this group are unicellular, do not possess a nucleus, and have peptidoglycan in their cell walls. An example of another organism in this taxonomic category is Streptococcus pyogenes.

Phylum
Shigella sonnei belongs to the phylum Proteobacteria because it is gram-negative with the outer membrane mainly composed of lipopolysaccharides. An example of another organism in this taxonomic category is Neisseria meningitidis.

Class
Shigella sonnei
is classified in the class Gammaproteobacteria because it is comprised of facilitative anaerobic and fermentative gram negative bacteria. An example of another organism in this taxonomic category is Legionella pneumophila .

Order
Shigella sonnei
fits into the Order Enterobacteriales because it is comprised of rod-shaped, facultative anaerobic, gram negative bacteria occurring as plant or animal parasites or as saprophytes. An example of another organism in this taxonomic category is Salmonella.

Family
Shigella sonnei
is classified into the family Enterobacteriaceae because members of this group grow well at 37 degrees Celsius, oxidase negative, and catalase positive, and reduces nitrates. An example of an organism in this taxonomic category is Escherichia coli.

Genus
Shigella sonnei
fits into the genus Shigella because it only causes disease in primates and no other animals. An example of an organism in this taxonomic category is Shigella flexneri.

Species
Classified as Shigella sonnei because it can be differentiated from the other types by positive β-D galactosidase and ornithine decarboxylase biochemical reactions.

 

Phylogentic Tree (Public Domain)

In the phylogenetic tree above, Shigella sonnei can be found in the Domain Bacteria. This diagram then breaks the Domain Bacteria into Gram-positive and Gram-Negative bacteria. Shigella sonnei can be the Gram-Negative bacteria within the Phylum Proteobacteria. This is a cladistics representation; the most primitive organisms, such as Shigella sonnei, are on the far left of the tree and the organisms’ complexity becomes greater as read to the right. This diagram shows how all the Domains fit together on one tree.

Phylogenetic Tree (Public Domain)

In the phylogenetic tree above, Shigella sonnei is being evolutionary compared to E. coli. This tree was made based on 100 genes that were randomly selected from 1,214 E. coli K12 genes. All strains of Shigella have been created by E. coli. It also shows how the closest Shigella strain to Shigella sonnei is Shigella boydii. The main that separates these two types of Shigella is how many serotypes each has. Shigella sonnei had 1 where Shigella boydii has 23. The tree branches colored in blue lead toward a pathogenic E. coli strain where the red tree branches lead toward a Shigella strain.

Now that we have spent some time on how Shigella sonnei came to be, lets take a look at its habitat!

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