Overview of the Types of Mouth Bacteria

The best word to describe the mouth environment would be “jungle”. Yes, the mouth is a jungle because it contains a large population of microorganisms which include bacteria, viruses, protozoa, and fungi. Bacteria have the largest population with 100 million for every milliliter of saliva belonging to more than 600 different species. The mouth is a diverse ecosystem with the microbes as the organisms and the teeth, saliva, tongue, gum as the microbial habitats. Even a person brushes his teeth thousand times; he could not totally eliminate mouth bacteria. Only a new born child has a sterile mouth, but once the child begin to take food, bacteria slowly starts colonizing the spaces of the mouth.

Now you know that there are hundreds of millions of bacteria in your mouth, don’t be alarmed because most of them are not harmful; as a matter of fact most of them are beneficial because they help control the population of harmful bacteria, viruses, protozoa, and fungi. The types of mouth bacteria depend on the environmental conditions inside the mouth. Acidity, alkalinity, temperature, host diet, and other factors affect the types of bacteria colonizing the mouth.

Let us look at some of the types of mouth bacteria especially those that cause dental carries and periodontal diseases.

Types of Human Mouth Bacteria

Staphylococci bacteria

-Staphylococci are bacteria that typically occur in clusters resembling grapes. Staphylococci species found in mouth include the Staphylococcus mutans and Staphylococcus sanguis. These bacterial species are the culprits for the formation of dental plaque and the eventual corrosion of teeth. These bacteria metabolize sugar (from the host food) and produce acids as by-products. The acids corrode the enamel through a series of chemical reaction leading to tooth decay.

There is an evolutionary theory saying that S. mutans and S. sanguis were previously not harmful bacteria in the mouth. When man began using refined sugar, the bacteria evolved over time to use sugar in their metabolism and release acids as by-products. Since the acids cause demineralization of the enamel, the bacteria became an enemy of man.

Porphyromonas gingivalis

-P. gingivalis is an anaerobic gram-negative bacteria associated with chronic adult periodontitis.

Treponema denticola

-This is a spirochete (spiral-shaped) bacterium thriving in the oral activity. Like P. gingivalis, T. denticola also causes periodontitis. This bacterium is motile and highly proteolytic (the ability to digest protein).


-These fusiform-shaped spirochetic bacteria live as normal organisms in the mouth and do not cause any harm. However, in the presence of wounds in the oral cavity (e.g. gum), fusospirochetes cause infection to the affected area.


-Veillonella is considered a beneficial bacterium because it slows down the development of dental caries by neutralizing the acidic metabolites of other bacteria like S. mutans and S. sanguis.


-These are rod-shaped, gram positive bacteria that can survive in the presence or absence of oxygen. Actinomyces naeslundii forms dental plaque by attaching to the surface of teeth.


-This bacterial genus belongs to the beta-proteobacteria group, bacteria capable of proteolysis. Although N. gonorrhea and N. meningitis cause gonorrhea and meningitis respectively, Neisseria species in the mouth are generally not harmful.


-Enterobacter species are gram-negative and facultative anaerobes that are commonly found in the gut of mammals but can also be found in the mouth. They are generally not harmful.


-This bacterial genus is normally symbiotic (mutual relationship) with humans and is normally found in the gut. Some species under this genus are associated with dental carries.