Streptococcus mutans: Difference between revisions

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==Application to Biotechnology==
==Application to Biotechnology==
Does this organism produce any useful compounds or enzymes?  What are they and how are they used?
Does this organism produce any useful compounds or enzymes?  What are they and how are they used?
''S. mutans'' does not produce any useful compounds or enzymes that are known in current study.


==Current Research==
==Current Research==

Revision as of 04:34, 26 August 2007

Streptococcus mutans. from [1]


Classification

Higher order taxa

Bacteria(Domain); Firmicutes(Phylum); Bacilli(Class); Lactobacillales(Order); Streptococcaceae(Family) (2).

Species

Streptococcus mutans (2).

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.


240px-streptococcus mutans 01.jpg

Streptococcus mutans is a Gram-positive bacteria that lives in the mouth. It can thrive in temperature ranging from 18-40 degress Celsius.It metabolizes different kinds of carbohydrates, creating acidic environment in the mouth as a result of this process. This acidic environment in the mouth is what causes the teeth decay. It is the leading cause of dental caries (tooth decay) worldwide. S. mutans is considered to be the most cariogenic of all of the oral Streptococci (8). S. mutans was first described by JK Clark in 1924 after he isolated it from a carious lesion, but it was not until 1960s that real interest in this microbe was generated when researchers began studying dental caries (8).

S. mutans is very important to study, not only because virtually everyone in the world carrys it, but also it has various symptoms that affect our daily lives. As the bacteria develops in the mouth, it causes teeth destruction, impaired speech, difficulty of chewing, multiple infections, psychological problems such as low self-esteem, poor social interactions, concentration problems, etc. Though not fatal, tooth decay is one of the most common infectious diseases in humans. also, cavities caused by the bacteria are the reason for half of all dental visits in the U.S. (6).

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 (7).

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 (4).

Cell structure and metabolism

OTSM.jpg

Streptococcus mutans is a Gram-positive bacteria, having a thick cell wall and retains a gentian violet. the cell wall is composed of peptidoglycan (murein) and teichoic acids that prevent osmotic lysis of cell protoplast and confer rigidity and shape on cell. S. mutans has a capsule that is composed of polysaccharide, and its structural subunit is dextran glucose. One of the virulence factors of S. mutans in cariogenicity is its ability to attach to the tooth surface and form a biofilm (11). S. mutans attach to surface, produce slime, divide and produce microcolonies within the slime layer, and construct a biofilm. It adheres specifically to the pellicle of the tooth by means of a protein on the cell surface. S. mutans grows and synthesizes a dextran capsule which binds them to the enamel and forms a biofilm some 300-500 cells. In the metabolism of S. mutans, it is able to cleave sucrose (after consuming carbohydrate provided by the animal diet) into glucose plus fructose. The fructose is fermented as an energy source for bacterial growth. The glucose is polymerized into an extracellular dextran polymer that cements S. mutansto tooth enamel and becomes the matrix of dental plaque. The dextran slime can be depolymerized to glucose for use as a carbon source, resulting in production of lactic acid within the biofilm (plaque) that decalcifies the enamel and leads to dental caries or bacterial infection of the tooth (10).

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 (3).

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 (5).

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 (6).

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 (3).

Application to Biotechnology

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

S. mutans does not produce any useful compounds or enzymes that are known in current study.

Current Research

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

1) In a current study conducted by a group of biologists from University of North Carolina and Washington University found that S. mutans ftf expressionwas affected by both the specific carbohydrate consumed and the age of the host animal. The fructosyltransferase gene (ftf) of S. mutans is a gene that directly associated with infection in the mouth (9). The ftf gene of S. mutans encodes the product fructosyltransferase, a enzyme that catalyzes the cleavage of sucrose, with subsequent polymerization of the fructose moieties into fructan, allowing it to remain in the dental plaque after its production (9). First, they fed animals with different types of carbohydraes: fructose, glucose and sucrose. then the bacteria activity was observed. As a result, there was the most bacterial activity found on sucrose, and activities on glucose and fructose were similar, which were only 1/3 of bacteria on sucrose (9). Second, animal age was examined as a potential factor of bacteria gene expression. In the result, young animals had been demonstrated to be more susceptible to the formation of dental caries than older animals. This study demonstrated animal age-dependent expression of an S. mutans virulence-associated gene whose product played an important role in the causation of dental caries (9).

2) Recently, researchers studied the role of WapA gene in S. mutans in cell surface structures, related functions, biofilm formation. Biofilm formation is one of the well-recognized virulence factors of S. mutans, which involves a sucrose independent initial attachment, cell–cell aggregation, a sucrose-dependent stabilization, and eventual biofilm muturarion (11). In order to study the role of WapA in cell surface structures and related functions, they constructed an isogenic mutant of WapA by insertional inactivation, then compared with wild type WapA gene(11). First, they labelled the wild type strain and mutant, and analyzed the architecture of biofilm, in order to see if the morphological change would affect the biofilm architecture. The result showed that the wild type cells fromed a biofilm with large but sparsely distributed microcolonies and large areas occupied by unstructured or sigle-cell chains. However, the mutant formed a thin biofilm and attached to the surface mostly as unstructured cell layers. Second, they tried to find the effect of WapA mutation on cell surface stickness of S. mutans. As they immobilized the two cells, they applied force to cell walls to observe the rupture event due to breakage of adhesive bond of each cell. The result showed that wild type cell was more sticky than the mutant. Lastly, they tested both wild type and mutant to see an effect of sucrose on gene expression. They measured the gene expression by PCR in absence and presence of sucrose. The result showed that both WapA wildtype and mutant gene expression were repressed by sucrose. The overall results suggested that the WapA protein plays an important structural role on the cell surface, which ultimately affects sucrose-independent cell–cell aggregation and biofilm architecture (11).

3) A recent study from the University of Heidelberg conducting by Dr. Geiss suggested that titanium, gold, natural enamel and amalgam alloy were superior to composite materials in reducing the adherence of Streptococcus mutans to dental restorations. In the in vitro study, 73 restorative material specimens were coated with cultured S. mutans and then examined with a scanning electron microscope for bacterial adherence (12). Dr. Geiss reported that in the absence of saliva, samples of titanium, gold, natural enamel and amalgam alloy had significantly less S. mutans adherence than Herculite XRV, a composite material manufactured by Kerr Dental (12). However, in the presence of saliva, bacterial adherence of S. mutans was reduced on the titanium and amalgam samples but increased in most of the other tested materials (12). This study also found that the least S. mutans adhered to specimens of titanium, a reactive metal that forms a passivating oxide layer. This findings were very signicant in dentistry because Titanium and titanium alloys were commonly used in dental implants and prostheses, crown fabrications, bridge frameworks, and denture frameworks (12).

References

1. Dennis Kunkel Microscopy. http://education.denniskunkel.com/catalog/product_info.php?products_id=9571

2. 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

3. 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

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

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

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

7. 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

8. European Bioinformatics Institute. http://www.ebi.ac.uk/2can/genomes/bacteria/Streptococcus_mutans.html

9. W. Todd Grey, Roy Curtiss III, and Michael C. Hudson. "Expression of the Streptococcus mutans Fructosyltransferase Gene within a Mammalian Host." Infection and Immunity, 1997. p. 2488-2490. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=175350

10. Structure and Function of Prokaryotic Cells. http://textbookofbacteriology.net/structure.html

11. Lin Zhu, Jens Kreth, Sarah E. Cross, James K. Gimzewski, Wenyuan Shi, and Fengxia Qi. "Functional characterization of cell-wall-associated protein WapA in Streptococcus mutans." A Journal of the Society for General Microbiology. http://mic.sgmjournals.org/cgi/content/full/152/8/2395

12. MedPage Today. http://www.medpagetoday.com/2005MeetingCoverage/2005ICAACMeeting/tb/4200

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