Oral Biofilm: Smart Bacteria in Your Mouth!

microscopic view of oral biofilm We know that brushing your teeth twice a day removes food debris and also bacteria that live on the teeth. Since there are 90 trillion cells in your body and only 10 percent of these are human, we should get to know these inhabitants that live and flourish in our bodies -- and especially those in our mouths. For many years we referred to the sticky substance formed on our teeth as plaque. The new word for this substance on our teeth is biofilm.

Biofilm is an association of bacteria that forms a unity on the surface. Bacteria live in biofilms wherever there is water, including oceans, sewers, water pipes and of course the oral cavity. Biofilms are very sophisticated systems and dental plaque is a classic biofilm.

Your mouth: what 1000+ species of bacteria call home

Development of a biofilm in the oral cavity begins with pioneer bacteria that form in the mouth of newborn infants. As the bacteria multiply, they change the environment and other bacteria begin to live and grow. This process continues and the diversity and complexity of the microbial community continues to increase. Around 500 different species have been isolated from an adult oral cavity. We know that there are at least 500 more species that exist but we cannot culture them; and we suspect that there may be hundreds more species that exist, but we do not have sophisticated enough equipment to identify them.

We might ask the question, where do these microorganisms come from? The infant gets its first group of bacteria from the caregiver, usually the mother. As mothers we hug, kiss and feed the infant. Our population of bacteria just slowly transfers over to the child. Bacteria from the air and from other people around the infant make up the rest of the population. How the microorganisms will manifest themselves in the infant's mouth and body depends on the genetic structure of the child, nutrition, immune system and so on.

From Pellicle to Biofilm

The development of oral biofilm is systematic. It begins when saliva coats the teeth and leaves a fine film called a pellicle. Certain bacteria capable of holding on to the enamel surface attach to this pellicle initially. Once attached, these microorganisms make up a sticky mass called an extracellular matrix or simply, goo. Since bacteria grow in little colonies, this mixture holds these microcolonies together. The sticky stuff on your teeth is actually 1/3 bacteria and 2/3 goo.

The oral biofilm consists of many similar groupings separated by a network of open water channels. Fluid moves through these tiny networks and bathes each group of microbes providing dissolved nutrients and removing waste products. The bacteria and matrix are densely packed and cemented together so they are difficult to dislodge.

The biofilm has many variations in chemicals and chemical reactivity and this affects the bacteria to the extent that one bacterium may look and act differently from the next even though they are genetically identical.

Trouble in Microbe City

Several species can live side by side and thrive. One species may feed on the metabolic waste of another. These cooperative populations are finely tuned and a simple disturbance may constitute a disease and produce symptoms.

When there is a disturbance in the balance of these populations, we may see conditions such as gingivitis and periodontitis develop. Often, there is no visible oral infection but there is an odour which we refer to as bad breath. Sometimes the affected individual also perceives an unpleasant taste. When there is an overgrowth of a microbial population, its metabolic by products are produced in greater amounts than can be used by the surrounding populations and are released into the saliva and subsequently into mouth air, giving it a distinct odour, often that of hydrogen sulfide or mercaptan or both.

In our next edition we will continue to discuss oral biofilm, how it develops and its ability to evade the immune system.


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