Streptococcus mutans

Classification

Higher order taxa

Bacteria(Domain); Firmicutes(Phylum); Bacilli(Class); Lactobacillales(Order); Streptococcaceae(Family) (1).

Species

Streptococcus mutans (1).

240px-Streptococcus_mutans_01.jpg

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.

Streptococcus mutans was first isolated JK Clark in 1924 from human carious lesions (cavities) and has known to be the main cause of tooth decay.

Streptococcus mutans is the leading cause of dental caries (tooth decay) worldwide and is considered to be the most cariogenic of all of the oral streptococci. Streptococcus mutans, sticks to the surface of teeth and subsists on a diverse group of carbohydrates. While metabolising sugar and other energy sources, the microbe produces acid that causes cavities in teeth.

S. mutans is carried by virtually everyone and the only other species common in man is S. sobrinus, carried by between 8 and 35% of people in different countries. Although S. mutans and S. sobrinus can be distinguished by appropriate laboratory tests, these are expensive and time-consuming so it is not always practicable to identify down to the species level in large-scale epidemiological studies.

Streptococcus mutans was first described by JK Clark in 1924 after he isolated it from a carious lesion but it wasn't until the 1960s that real interest in this microbe was generated when researchers began studying dental caries in ernest. Researchers have identified several hundred genes that appear to be unique to the organism. These are potential drug targets because disrupting them would disable the pathogen without harming other bacteria in the mouth.

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?

The genome of S. mutans UA159, a serotype c strain, has been completely sequenced and is composed of 2,030,936 base pairs. It contains 1,963 open reading frames, 63% of which have been assigned putative functions. almost 300 appear to be unique to S. mutans. previously, only three genes for glucan-binding proteins have been isolated, but genome sequesncing has uncovered a potential fourth gene, gbpD. genes associated with transport system are account for almost 15% of the genome. Virulence genes associated with extracellular adherent glucan production, adhesins, acid tolerance, proteases, and putative hemolysins have been identified. Strain UA159 is naturally competent and contains all of the genes essential for competence and quorum sensing. there are no bacteriophage genomes are present in S. mutans (6).

S. mutans is composed of circular DNA, and has at least three closely related, but different plamids. the size of these plasmids are similar which is approximately 5.6 kilobase(kb). these plasmids are important to S. mutans because of their functions including resistance to certain anti-biotics or heavy metals, bacteriocin production and immunity, accessory catabolic pathways and mechanisms for conjugation-like transfer activities (3).

Cell structure and metabolism

Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.

Ecology

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

the association of S. mutans in dense biofilms on the teeth suggests that S. mutans may affect other plaque bacteria in the mouth. in fact, earlier studies have shown that there is an inverse relationship between the quantity of S. mutans in dental plague and the presence of another bacterim named Streptococcus sanguinis. the study shows that S. mutans antagonize the growth of S. sanguinis via either acid production or the elaboration of bacteriocins (2).

Pathology

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

Streptococcus mutans is an animal parasite, especially for animals have high carbohydrate (sucrose, fructose, and glucose)diet, and is well known as primitive causative agent of dental caries in humans (4).

S. mutans is the main contributor to tooth decay, and is mostly found on surfaces of tooth. when food containing carbohydrates is consumed, S. mutans interact with it and produce acids that cause mineral loss from teeth. the tooth cavity is the result of this mineral loss, and it can eventually destroy the whole tooth. tooth decay can spread in the mouth, and can cause extreme pain with difficulty of chewing. several infections caused by S. mutans can even result a death in extreme cases (5).

some virulence factors of S. mutans are found that distinguish S. mutans strains from other oral streptococci isolated from the human oral cavity. first, s. mutans is able to synthesize insoluble adhesive glucans from sucorse. second, it has relatively more acid tolerance (aciduricity). third, it has a rapid production of lactic acid from dietary sugars. also, a number of genes that influence the virulence are found. These genes include gtfB, gtfC, and gtfD genes coding for glucosyltransferases, the gbpA and gbpC genes encoding glucan-binding proteins, spaP expressing a cell surface adhesion, and the glgR gene involved in intracellular polysaccharide storage. In addition, a number of other genes that have been shown to affect potential virulence properties in vitro are also characterized, including some involved in the stress responses of S. mutans. These genes are ffh, dgk, gbpB, and an apurinic-apyrimidinic endonuclease gene (2).

Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

Enter summaries of the most recent research here--at least three required

References

1. National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=1309&lvl=3&lin=f&keep=1&srchmode=1&unlock

2. Vincent A. Fischetti, Richard P. Novick, Joseph J. Ferretti, Daniel A. Portnoy, and Julian I. Rood. "Gram-Positive Pathogens." 2nd ed. Washington: American Society for Microbiology press, 2006

3. Shigeyuki Hamada, Suzanne M. Michalek, et al. "Molecular Microbiology and Immunobiology of Streptococcus mutans." New York: Elsevier Science, 1986

4. Infection and Immunity by the American Society for Microbiology. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=175350

5. National Maternal and Child Oral Health Resource Center. http://www.mchoralhealth.org/openwide/mod1_2.htm

6. National Center for Biotechnology Information. http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=12397186&dopt=AbstractPlus&holding=f1000%2Cf1000m%2Cisrctn

Edited by [duk002@ucsd.edu Dustin Kim], student of Dr. LarsenRachel Larsen