Streptococcus sobrinus
Streptococcus sobrinus is a Gram-positive, catalase-negative, non-motile, and anaerobic member of the genus "Streptococcus". Pathology. "Streptococcus sobrinus" in conjunction with the closely related species "Streptococcus mutans" are pathogenic within humans and enhances the formation of caries within teeth. Biofilm from the mixture of sugar and plaque create a suitable environment for "S. sobrinus" to grow. "S. sobrinus" is more closely connected with the prevalence of caries than "S. mutans". "S. sobrinus" is also affiliated with early childhood caries, which are responsible for the majority of dental abscesses and toothaches in children. Children generally acquire "S.  sobrinus" strains from their mother, but the relatively high consumption of sugars by minors facilitates bacterial growth and threatens the onset of early childhood tooth decay. "S. sobrinus" has also been documented within the teeth of rats. History. "Streptococcus sobrinus" was discovered by the French biologist Louis Pasteur in 1887 along with other human pathogens. The full genome of "S. sobrinus" has been sequenced, and the related species "S. mutans" has also been fully sequenced. Symbiosis. Extracellular long-chained glucans synthesized from sucrose via glucosyltransferase enzymes help accumulate "S. sobrinus" on tooth enamel surfaces. The glucans provide a shelter for  bacterial colonization, and the protected environment creates the perfect nesting ground for "S. sobrinus" and other microorganisms to sustain a stable community in the form of dental plaque. "S. sobrinus" in turn releases lactic acid in the anaerobic metabolism of glucose. Lactic acid demineralizes tooth enamel and fosters the initiation of dental caries. "S. sobrinus" has an optimal growth temperature of 37 °C and thrives in a slightly acidic environment at a pH of 6.3. This makes the human mouth a suitable habitat due to its acidic characteristics, favorable body temperature, and significant amount of food sugars passing through  the mouth on a daily basis. However, these traits also indicate that "S. sobrinus" has a difficult time surviving outside the host of the human teeth. Antibacterials. In 1995 a paper by Meurman et al. tested "Lactobacillus" rhamnosus for inhibitory properties, although this relationship was only observed with a weak correlation at a pH below 5. Lectin from "Talisia esculenta" and Labramin from "Labramia bojeri" seeds were found to inhibit the adherence of "S. sobrinus" to tooth enamel, but had no effect on the growth of the population itself. A study by Sun et al. in 2009, tested a vaccine  for "S. sobrinus", and initial tests have been successful in providing protection.