Streptococcus mitis
A Microbial Biorealm page on the genus Streptococcus mitis
Classification
Higher order taxa
Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae;
Species
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NCBI: Taxonomy |
Streptococcus mitis
Description and significance
Streptococcus mitis are commensal bacteria that colonize hard surfaces in the oral cavity such as dental hard tissues as well as mucous membranes and are part of the oral flora. They are usually arranged in short chains in the shape of cocci (10). These Gram-positive bacteria are not usually pathogenic but commonly cause bacterial endocarditis, which is the inflammation of an inner layer of the heart. S. mitis are alpha hemolytic, meaning it can break down red blood cells. S. mitis are not motile, do not form spores and lack group-specific antigens (2). S. mitis live optimally at temperatures between 30 and 35 degrees Celsius, making them mesophiles. They are facultative anaerobes, which is a bacterium that makes ATP by aerobic respiration if oxygen is present but is also capable of switching to fermentation in the absence of oxygen (7).
Genome structure
The genome of S. mitis has been sequenced and consists of a circular chromosome with about two million bp that varies with different strains. Its GC and AT content are respectively 40.4% and 59.1%. There are a total of 2222 genes of which 2149 are protein coding genes (3).
The genes encoding the lipoproteins Pb1A and Pb1B in S. mitis are clustered close to the genes that are very similar to the streptococcal phages r1t, 01205 and Dp-1. This implies that Pb1A and Pb1B might be located within a prophage (4). To test this possibility, mitomycin C and UV light were used because both can induce the lytic cycle of many phages. Cultures of S. mitis were exposed to this and a significant increase expression of Pb1A and Pb1B were detected by Western blot analysis. Phage particles were visible in the cultures of S. mitis, which was named SM1. This phage had a DNA genome of about 35 kb. All these experiments concluded that Pb1A and Pb1B are encoded by a lysogenic bacteriophage (4).
Cell structure and metabolism
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Ecology
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Pathology
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Application to Biotechnology
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Current Research
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References
Edited by student of Rachel Larsen
