Streptococcus mitis

Streptococcus mitis
Scientific classification
Domain:	Bacteria
Phylum:	Bacillota
Class:	Bacilli
Order:	Lactobacillales
Family:	Streptococcaceae
Genus:	Streptococcus
Species:	S. mitis
Binomial name
Streptococcus mitis Andrewes and Horder 1906 (Approved Lists 1980)
Synonyms
Streptococcus mitior[1]

Streptococcus mitis is a species of Gram-positive, mesophilic, alpha-hemolytic bacteria in the genus Streptococcus. These bacteria are facultative anaerobes, and made up of non-motile and non-sporing cocci (round cells) that are catalase negative. It is a commensal and commonly inhabits the human mouth, throat, and upper respiratory tract, as part of the oral microbiota. They are clinically important for humans, as under certain conditions, it can cause opportunistic infections, such as infective endocarditis.^[2]

Members of the Streptococcus genera belong to lactic acid bacteria defined by the formation of lactic acid as an end-product of carbohydrate metabolism. The family Streptococcaceae is characterized by based upon its 16S rRNA gene sequence analysis within the low (< 50 mol%) G+C branch. There are over 50 species in the genus which are classified by their 16S rRNA sequences.^[3]

Streptococcus mitis primarily resides in the oral cavity which includes the mouth, nasopharynx, and throat. However, there have also been cases of it in the female genital tract, the gastrointestinal tract, and even on the skin.^[4]

S. mitis is competent for natural genetic transformation. Thus S. mitis cells are able to take up exogenous DNA and incorporate exogenous sequence information into their genome by homologous recombination.^[2] These bacteria can employ a predatory fratricidal mechanism for active acquisition of homologous DNA.^[2]

It has been reported that Streptococcus mitis identified and survived for over two years on the Surveyor 3 probe on the Moon. However, NASA stated that this is most probably due to contamination upon return to Earth. The Apollo 12 crew received pieces of Surveyor in 1969, one of these was the TV camera. The probe was then analyzed to consider how the lunar environment affected the material. Surveyor 3 had not been sterilized before its launch because scientists wanted to see if organisms could survive the two and half years on the Moon, so looking for surviving organic material was a part of this analysis. ^[5]

Upon inspection, a group found an amount of S. mitis inside a piece of foam located inside the camera. Culture plates were made and the identity was later confirmed as Streptococcus mitis at the US Communicable Disease Center at Atlanta, Georgia. At first, it was speculated that S. mitis had been picked up from the Moon but research later discovered that the residence of the bacteria on the probe had started after the probe returned.^{[citation needed]}

• S. mitis subdural empyema from MedPix
• Type strain of Streptococcus mitis at BacDive - the Bacterial Diversity Metadatabase

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