We all know that it is important to brush our teeth, but did you know that even with excellent hygiene there is still an estimated 500,000 bacteria on each tooth? This may sound alarming and maybe even concerning, but don’t worry because most of the bacteria that are in your mouth cause no harm and some even have a beneficial effect. The first bacteria were viewed by Antonie Van Leeuwenhoek in 1683. He took cells from his cheek and examined the sample under his homemade microscope (Avila et al. 2008). As previously mentioned microorganisms can have a wide variety of relationships with its host. In the oral microbiome most cells either don’t affect its host or can be helpful, however there are cases where bacteria can be pathogenic and dangerous to its host, often times causing disease. The exact trigger of what causes bacteria to go from having no effect to being dangerous is unknown, however there are two main theories. Theory one says that the bacteria associated with a host present in the mouth have always been in the pathogenic state but have been outnumbered by non-harmful bacteria and never had the opportunity to grow, until they did. Theory two says that the bacteria change due to an environmental change. There is currently an estimated 750 unknown microbial cells living in the human mouth waiting to be discovered but studying the oral microbiome is challenging because it is difficult to replicate the environment accurately. There is however a technique for studying the microorganisms in the mouth called metagenomics. This process is able to analyze large amounts of microbial families. Metagenomic sequencing is much faster and more accurate than grow individual communities to study. Previous studies have found a positive health correlation between a high concentration of P. gingivalis, Tannerella forsythia, and Actinobacillus in healthy mouths. Knowing the microorganisms that inhabit a person’s mouth is crucial for understanding what interactions are taking place and can lead to improving medical and health practices.
There is the same amount of prokaryotic organisms living in/on a person as the amount of eukaryotic cells that make up the human body. There are many different types of cells in the human oral microbiome, some are commensal, some are beneficial and some are pathogenic. Studies are currently looking at why cells become pathogenic and have come up with two theories. The first one theorizes that certain host associated cells in the oral environment have always been pathogenic, however they were overpopulated by commensal cells and were held at bay until they had the opportunity to grow. The second theory states that an environmental change occurs which triggers the bacteria the change into pathogenic cells. Since the oral microbiome is extremely difficult to replicate, studying the environment and cells that live in it can be challenging. However metagenomic sequencing has made a large difference in the ability to identify large communities of microbes at once. This is much more accurate and time efficient than isolating the different microorganisms. Isolating individual microbes can also be challenging since only a small amount will show up on swab plates. Studies previously performed have found a correlation between people with good hygiene and a healthy microbiome, having high concentrations of P. gingivalis, Tannerella forsythia, and actinobacillus. There is still so much to be discovered about the human oral microbiome, there is an estimated additional 750 host associated microbial cells yet to be discovered in the human mouth.