Streptococcus salivarius

From MicrobeWiki, the student-edited microbiology resource

A Microbial Biorealm page on the genus Streptococcus salivarius

Classification

Higher order taxa

Bacteria; Firmicutes; Bacilli; Lactobacillales; Streptococcaceae; Streptococcus; Streptococcus salivarius

Species

NCBI: Taxonomy

Streptococcus salivarius

Description and significance

Streptococcus salivarius is the principal commensal bacterium of the oral cavity in healthy humans. Normal inhabitant of the upper respiratory tract - trauma (dental work, brushing teeth, etc.) results in organisms entering into the blood stream. It is the first bacterium which colonizes the dental plaque, before being joined by numerous other species of various genera. It therefore seems to be the pioneer in colonizing dental plaque, creating favorable conditions for the implantation of other species, but also a bacterium which plays the role of moderator, permitting the implantation of bacteria which are harmful to the health of the oral cavity.

A better knowledge of the molecular and physiologic factors which allow it to colonize dental plaque and to interact with other species will help in designing strategies for the prevention of cavities, especially in children.

Genome structure

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

S. salivarius contains fimbriae on their cell surface. Fimbriae are hair-like appendages that are composed of protein subunits with diamters ranging from 2-8 nm. Fimbriae are involved in coaggregation of S. salivarius with the periodontopathogen Prevotella intermeida.

Ecology

Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.

Pathology

How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.

Application to Biotechnology

Streptococcus salivarius secretes a glucosltransferase (Gtf) which froms a glucan from sucrose. S. Salivarius is one of the main sources of Gtf in saliva and in the acquired pellicle is believed to be from S. salivarius resident on the dorsum of the tongue. Gtfs incorporated in the pellicle are known to be active and to form glucans to which other oral streptococci, such as the mutans streptococci, are able to adhere. Thus, Gtfs produced by S. salivarius at sites distant from the tooth surface may aid in the initial attachment or entrapment of other oral species on newly erupted tooth surfaces or on tooth surfaces following prophylaxis.

Also secretes an enzyme named urease. Urease can catalyze the hydrolysis of urea to ammonia and carbon dioxide.

Current Research

A new research found results that suggest Gram-positive micro-organisms such as S. salivarius contribute to oral malodor production by deglycosylating salivary glycoproteins, thus exposing their protein core to further degradation by Gram-negative micro-organisms. Studies show a direct link between low levels of Streptococcus salivarius in the mouth throat and tonsils and the development of halitosis.

References

Lévesque, Céline, ChristianVadeboncoeur, and MichelFrenette. 2004. "The csp operon of Streptococcus salivarius encodes two predicted cell-surface proteins, one of which, CspB, is associated with the fimbriae". Microbiology 150 (Pt 1): 189-98.

N. Sterer1, and M. Rosenberg "Streptococcus salivarius Promotes Mucin Putrefaction and Malodor Production by Porphyromonas gingivalis". "Journal of Dental Reserach".

[http://iai.asm.org/cgi/content/abstract/63/2/609 Simpson, CL. "Streptococcus salivarius ATCC 25975 Possesses at Least Two Genes Coding for Primer-Independent Glucosyltransferases". 1995. "Infection and Immunity" p. 609-621.]

http://www.cns.fr/externe/English/Projets/Projet_MB/organisme_MB.html

Edited by Artin Meserkhani, a student of Rachel Larsen and Kit Pogliano