User:DiekhoffB

Classification

Higher order taxa

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

Species

NCBI: Taxonomy

Streptococcus mutans

Description and significance

S. mutans was discovered in 1924 by a man named JK Clark, whom was studying dental caries at the time of discovery. The bacterium was withdrawn from a patient's decaying tooth, observed, and described by Clark (4). S. mutans is a Gram positive bacteria that possesses anaerobic capabilities and is non-motile (2). These bacteria reside in the mouths of humans and have not been found elsewhere. There are other species of streptococci that have been found to live in the mouth of other organisms. S. mutans also produces acid, which allows it to break down the enamel on teeth in order to dig into them. S. mutans can affect health beyond the mouth, though. Poor dental hygiene allows for the bacterium to easily break down teeth with no set backs, resulting in lower health of the body as a whole. Plaque made by S. mutans can enter the bloodstream, and loss of teeth and development of gum disease can affect one's diet (6). If the teeth are not taken care of and cavities are not prevented, S. mutans can inflict a huge amount of damage.

Describe the appearance, habitat, etc. of the organism, and why you think it is important.

"Figure 1. A Gram stain of S. mutans shows its Gram positive character along with its clustered and chain growing patterns.".

Genome structure

The genome of S. mutans includes 2,030,936 base pairs total (1). To contain these base pairs, the bacterium possesses three separate chromosomes comprised of DNA in a circular form. In this sequence of base pairs in the chromosomes, the bacterium's ability to survive in the mouth is evident. About 15% of the genome is comprised of sequences that code for transport pathways for its different metabolic pathways (1). Because of its ability to continue metabolism without oxygen, the genome includes sequences for multiple metabolic pathways. In addition, the bacterium is able to break down a myriad of carbohydrates due to its large number of enzymes encoded in its genome. This allows for the bacterium to outcompete many of the other bacteria in the mouth.

Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence?

Cell structure and metabolism

A unique quality of the cell wall of S. mutans is that it lacks antigens for B cells of the body's immune system (5). This means that it is undetectable by the B cells of the immune system, allowing it to survive more easily in the mouth of humans.

S. mutans is a facultative anaerobe, which means it can undergo metabolism in aerobic conditions, but if oxygen is not present, it is able to change pathways to anaerobic respiration (7).

Interesting features of cell structure; how it gains energy; what important molecules it produces.

Ecology

Being a bacteria that causes cavities, S. mutans dwells in the mouths of humans where it creates plaque. The amount of S. mutans in the human mouth ranges from about 30 - 60% of the total bacteria present on all surfaces in the mouth. This bacterium often outcompetes the rest of the mouth dwelling bacteria, due to its versatility, but other species of streptococcus are seen to cause dental caries along with S. mutans. S. mutans also possesses the ability to create a polysaccharide called dextran, which is sticky. This allows the bacterium to adhere to the surface enamel, making its job easy to do. This bacterium thrives off of the sugars from the food humans ingest and the warm temperature of the mouth is an ideal number for the bacterium to undergo metabolism and replication. Salivary glands continually wash S. mutans and all other bacteria from the mouth naturally, and this process is aided by regular teeth brushing. Absence of dental hygiene and a dry mouth give the bacterium a perfect opportunity to do damage to the teeth because they are not being removed form the tooth surfaces, but being left to produce acid and seep into the inner tooth.

Habitat; symbiosis; contributions to the environment.

Pathology

S. mutans is a bacteria of the normal flora of the mouth, which undergoes natural processes that create acid and the breaking down of teeth and bone. In addition to dental caries, S. mutans can lead to gum disease and periodontitis (3). Both of these involve the inflammation and recession of the gums, which then leads to teeth loss. Generally, teeth loss can lead to a speech impediment and under-nutrition of an individual. Essentially, lack of proper dental hygiene does not stop its harmful effects at the mouth, but affects the entire body. S. mutans, along with other mouth dwelling bacteria, can cause this process to occur.

The effects of S. mutans can normally be caught before a tooth is lost by a dentist. A dentist is able to see decay indicated by brown spots on a tooth, or by feeling soft spots on teeth with a dental pick. Depending on how long the bacterium has been working, the patient may or may not feel pain or sensitivity to hot and cold even if the doctor can see a cary beginning to form.

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

Current Research and or Application to Biotechnology

Because S. mutans is a main bacteria that breaks down teeth to cause dental caries, many scientist have attempted to create a vaccine in order to eliminate it from the natural flora of the mouth. But, these vaccines have worked on a biological standpoint, but the economics of the vaccine were impractical. The vaccines are very expensive compared to regular dental hygiene, such as brushing teeth, flossing and using mouthwash. While dental hygiene does not completely eliminate the bacterium, it does prevent the formation of caries if done routinely.

Additionally, many naturally occurring minerals and substances function as a natural antibiotic or reverse the damage of S. mutans on the surface of teeth. One of these substances being green tea. The chemical make up of green tea includes a molecule called polyphenol, which prevents the bacterium from utilizing the sugar in the mouth from ingested foods. This does not allow the bacteria to undergo normal processes such as the production the sticky secretions, which allow them to stick to teeth, and the production of acid to break down the enamel on teeth. Essentially, polyphenols block cell metabolism, which prevents normal action of the bacteria, lowering the possibility of dental caries. Because of this, there are many products like tea and chewing gum that use green tea extract.

Recent studies have revealed that the uncontrolled presence of S. mutans is linked to heart disease. Without routine dental hygiene, S. mutans is able to build up on teeth and cause plaque. This plaque can be broken off from the teeth during mastication and ingested into the body. From there, the plaque can enter the blood stream and cause blockages in arteries in the heart and also the hardening of arteries. Before this discovery, the effects of S. mutans were believed to be

Enter summaries of the most recent research and/or application to biotechnology here--at least three required

References

1.) Adjic, D., and W. M. McShan. "Genome Sequence of Streptococcus Mutans UA159, a Cariogenic Dental Pathogen." Proceedings of the National Academy of Science 22 (2002).

2.) Bergey, D. H., and John G. Holt. "Bergey's Manual of Determinative Bacteriology." 9th ed. Baltimore: Williams & Wilkins, 1994. Print.

3.) Horiba N, Maekawa Y et al. A pilot study of Japanese green tea as a medicament: antibacterial and bactericidal effects. J Endod. 1991 Mar;17(3):122-4.

4.) Klein, P., and M. Scholler. "Recent Advances in the Development of a Streptococcus Mutans Vaccine." European Journal of Epidemiology 4.4 (1988): 419-25.

5.) Mukasa, Hidehiko, and Hutton D. Slade. "Structure and Immunological Specificity of the Streptococcus Mutans Group B Cell Wall Antigen." American Society for Microbiology 7.4 (1973): 578-85

6.) Nakano, K., H. Inaba, R. Nomura, et al. "Detection of Cariogenic Streptococcus Mutans in Extirpated Heart Valve and Atheromatous Plaque Specimens." Journal of Clinical Microbiology 44.9 (2006): 3313- 317.

7.) O'Leary, William M. "Practical Handbook of Microbiology." Boca Raton, FL: CRC, 1989. Print.

8.) Thomas, E.L., and Pera, K.A. "Oxygen metabolism of Streptococcus mutans: uptake of oxygen and release of superoxide and hydrogen peroxide." American Society for Microbiology 154.3 (1983): 1236-1244

Edited by student of Dr. Lynn M Bedard, DePauw University http://www.depauw.edu