| Streptococcus mitis | |
|---|---|
Scientific classification | |
| Domain: | Bacteria |
| Kingdom: | Bacillati |
| 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 aspecies ofGram-positive,mesophilic,alpha-hemolyticbacteria in the genusStreptococcus, belonging to theviridans streptococci group. These bacteria arefacultative anaerobes, and made up of non-motile and non-sporingcocci (round cells) that arecatalase negative. It is acommensal and commonly inhabits the human mouth, throat, and upper respiratory tract, as part of theoral microbiota. They are clinically important for humans, as under certain conditions, it can causeopportunistic infections, such asinfective endocarditis.[2]
Members of theStreptococcus genera belong tolactic acid bacteria defined by the formation oflactic acid as an end-product ofcarbohydrate metabolism. The familyStreptococcaceae is characterized by based upon its16S 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 fornatural genetic transformation. ThusS. mitis cells are able to take upexogenous DNA and incorporate exogenous sequence information into their genome byhomologous recombination.[2] These bacteria can employ a predatory fratricidal mechanism for active acquisition of homologous DNA.[2]
It has been reported thatStreptococcus mitis identified and survived for over two years on theSurveyor 3 probe on the Moon. However, NASA stated that this is most probably due to contamination upon return to Earth. TheApollo 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 ofS. mitis inside a piece of foam located inside the camera. Culture plates were made and the identity was later confirmed asStreptococcus mitis at the US Communicable Disease Center at Atlanta, Georgia. At first, it was speculated thatS. 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]
| Test type | Test | Characteristics |
|---|---|---|
| Biochemical characters | Gram stain | Positive |
| Catalase | Negative | |
| Oxidase | Negative | |
| 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 |
