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]
| 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] | |
Classification
editMembers 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]
Habitat
editStreptococcus 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]
Natural genetic transformation
editS. 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]
Moon Surveyor 3 probe
editApproach
editIt 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]
Results
editUpon 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]
Characteristics of Streptococcus mitis
edit| Test type | Test | Characteristics |
|---|---|---|
| Biochemical characters | Gram stain | Positive |
| Catalase | Negative | |
| Oxidase | Positive | |
| Methyl Red | Positive | |
| Voges Proskauer (VR) | Negative | |
| Coagulase | Negative | |
| DNase | Negative | |
| Morphological characters | Shape | Coccus |
| Arrangement | Chains or pairs | |
| Fermentation | Glucose | Positive |
| Fructose | Positive | |
| Galactose | Positive | |
| Lactose | Positive | |
| Maltose | Negative | |
| Mannitol | Variable | |
| Mannose | Positive | |
| Sucrose | Positive | |
| Starch | Negative | |
| Enzymatic Reactions | Acetoin | Negative |
| Acid Phosphatase | Variable | |
| Alkaline Phosphatase | Positive | |
| Hyaluronidase | Negative | |
| β-D-glucosidase | Positive | |
| Leucine aminopeptidase | Positive | |
| Neuraminidase | Positive |
References
edit- ^ Gross KC, Houghton MP, Roberts RB (September 1981). "Evaluation of blood culture media for isolation of pyridoxal-dependent Streptococcus mitior (mitis)". J. Clin. Microbiol. 14 (3): 266–72. doi:10.1128/jcm.14.3.266-272.1981. PMC 271953. PMID 7287885.
- ^ a b c Johnsborg O, Eldholm V, Bjørnstad ML, Håvarstein LS (2008). "A predatory mechanism dramatically increases the efficiency of lateral gene transfer in Streptococcus pneumoniae and related commensal species". Mol. Microbiol. 69 (1): 245–53. doi:10.1111/j.1365-2958.2008.06288.x. PMID 18485065. S2CID 30923996.
- ^ a b Sapkota, Anupama (2021-01-06). "Streptococcus mitis- An Overview". Microbe Notes. Retrieved 2022-05-04.
- ^ Kutlu, Selda Sayin; Sacar, Suzan; Cevahir, Nural; Turgut, Huseyin (2008-11-01). "Community-acquired Streptococcus mitis meningitis: a case report". International Journal of Infectious Diseases. 12 (6): e107–e109. doi:10.1016/j.ijid.2008.01.003. ISSN 1201-9712. PMID 18378176.
- ^ "Surveyor 3 Streptococcus mitis (APSTREPMIT)". NASA. Retrieved 27 December 2015.
External links
edit- S. mitis subdural empyema from MedPix
- Type strain of Streptococcus mitis at BacDive - the Bacterial Diversity Metadatabase
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