Our insides are populated by bacteria, fungi and viruses: what we know about microbes in the mouth

It is a diverse community that inhabits our mouths: everyone has around 250 species of microbes in the space between the lips and throat, and researchers know of a total of around 700 species.

Our insides are populated by bacteria, fungi and viruses: what we know about microbes in the mouth

It is a diverse community that inhabits our mouths: everyone has around 250 species of microbes in the space between the lips and throat, and researchers know of a total of around 700 species. This community, the so-called microbiome, varies from person to person like a fingerprint. Their composition depends, among other things, on what we eat, how well we clean our teeth and tongue, and with whom we exchange microbes. In partners who kiss regularly, the microbiomes get closer to each other. Children take part of their microbial community with them at birth.

Some microbes accompany us throughout our lives, others are only there on flying visits, for example when we have a cold. Many of the mouth dwellers live in peaceful coexistence with us, while some others cause lasting damage. For example, the bacterium Streptococcus mutans and the yeast fungus Candida albicans. Both are instrumental in causing our teeth to break. This is because when they are fed sugar, they give off acids that destroy tooth enamel and cause tooth decay.

Sometimes the microbes even band together against us. Researchers at the University of Pennsylvania have discovered in the saliva of children with severe tooth decay that bacteria and fungi apparently form a kind of community. Not only do they attack the teeth individually, they also act together as what the researchers say is a superorganism. The immobile bacteria dock onto the surface of the mushrooms and travel along like hitchhikers as the mushrooms grow. This allows the bacteria to reach new refuges and then spread there.

The superorganism has other properties that make life easier for bacteria and fungi: in a double pack, they multiply faster than each on its own. They form a stable biofilm that is difficult to scrub away. They are resistant to antibiotics. Researchers suspect that if this group of microbes could be dissolved, it could possibly prevent tooth decay. They do not yet know whether and how this will succeed.

Despite harmful microbial communities, the situation in German mouths is quite good. According to the most recent German Oral Health Study from 2014, 81 percent of twelve-year-old children have caries-free teeth, compared to only 42 percent in 1997. Dental health had also improved noticeably among young adults over the same period. In the dentures of 35 to 44 year olds there were an average of eleven teeth with cavities in 2014, a significant decrease. There has also been progress in the treatment of gingivitis or periodontitis. While 71 percent of young adults still had problems with it in 2005, it was 52 percent in 2014.

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