Dental Plaque - Biotic Relationships

Biotic Relationships

The microorganisms in the oral cavity live with one another in commensal or mutualistic symbiotic relationships. Typically, anaerobic bacteria would succumb to high levels of oxygen, but with the redox reactions discussed in the previous section they are able to survive. This commensal relationship allows a mixture of aerobic and anaerobic bacteria to live in the same area. The formation begins by the adsorption of early colonizers onto an acquired pellicle through chemical processes. An acquired pellicle is a layer of saliva that is composed of mainly glycoproteins and forms shortly after cleaning of the teeth or exposure of new teeth. These bound early colonizers manipulate the environment for the immediate benefit of other bacteria. Once the environment has been manipulated other bacterial colonizers are able to co-adhere to the early colonizers. This is done repeatedly resulting in layers of bacteria. Once new bacterial cells co-adhere to one another they gain the ability to communicate to one another. They are able to communicate to one another through a biochemical process called quorum –sensing. Quorum –sensing virtually allows all the bacteria to benefit from one another. This ability can allow a bacterium to feel the presence of other bacteria around it. Due to this communication, bacteria have the ability to change their genotype (and thus their phenotype) as a result of population concentration and/or environmental changes to remain as competent competitors. These relationships tend to exhibit homeostasis until there is some type of disruption in the ecosystem.

The most common reasons for ecosystem disruption are the ecological factors that were discussed in the environment section. The bacteria that exhibits the most fit plasticity for the change in environment dominates the given environment. Often, this could lead to opportunistic pathogens that lead to dental caries and periodontal disease. Pathogens that have the potential to cause dental caries flourish in acidic environments. Pathogenic bacteria that have the potential to cause periodontal disease flourish in a slightly alkaline environment.