A Microbial Biorealm page on the genus Streptococcus gordonii
Higher order taxa
Bacteria; Firmicutes; Lactobacillales; Streptococcaceae; Streptococcus
Description and significance
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Dental plaque biofilm formation begins with pioneer organisms which attach to tooth surfaces in the human oral cavity. Streptococus gordonii is one of these pioneer organisms which initiate colonization and assist the further colonization of other organisms including Porphyromonas gingivalis, a periodontal pathogen.
In a recent study, S. gordonii was found to contain essential genes that facilitate the accrual of free floating P. gingivalis cells into the beginnings of a functioning biofilm. These genes were integral components in extracellular capsule biosynthesis, intercellular or intracellular signaling, biofilm architectural development and maintainance of adhesive proteins.
Initialy, Streptococcus gordonii initiates colonization through formation of a monospecies biofilm. S. gordonii cells at the surface of the tooth initiate a signal transduction pathway, known as BrfAB, which regulates adhesive activity. The S. gordonii monospecies biofilm then acts as a binding site for attachment of other more pathogenic organisms such as P. gingivalis by a process called coadhesion. Specifically, the long fimbriae (FimA) of P. gingivalis binds to glyceraldehydes-3-phosphate dehydrogenase (GAPDH) contained in the S. gordonii surface. The short fimbriae (Mfa) of P. gingivalis allows the cells to interact with the streptococcal SspA/B (antigen I/II) adhesions via an 80 amino acid binding epitope of SspA/B (BAR).
Human volunteers who have introduced P. gingivalis into their mouths have shown that P. gingivalis is found solely in areas of streptococcal rich plaque. Furthermore, biofilms between P. gingivalis and other streptococci, such as Streptococcus mutans and Streptococcus cistatus, are nonexistent. S. gordonii, therefore, may influence the constituents of oral biofilms by the specificity of adherence and signaling mechanisms. In in vitro studies, P. ginigivalis was also shown to coadhere with S. gordonii and this binding interaction promotes degradation of dentinal tubules by the otherwise non-dentin invasive P. gingivalis.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.