Tongue bacteria. Image courtesy of Steve Gschmeissner
That’s a mouthful
This week, Rob Stein at NPR concluded his series on the human microbiome with a look at research investigating how our multitudinous intestinal bacteria may influence brain development and function. Turns out that old notion about “gut feelings” might have a biological basis.
These days, microbiome research is on everybody’s tongue, and thus the inspiration for today’s image: a colorized scanning electron micrograph of bacteria residing on a human tongue.
It should be no surprise that the human mouth is home to hundreds of microbial species. After all, it’s warm, moist and frequently open for business. It doesn’t start that way. A newborn has no bacteria in its oral cavity, but that soon changes – and changes even more as the mouth develops. Gums, cheeks and emerging teeth all provide distinct environmental niches for different bacterial species.
Some of these species are beneficial, aiding in digestion, for example. Many others are offer no direct benefit, but are helpful in occupying space that might otherwise be taken up by nastier bugs, such as those that cause tooth decay, periodontal diseases and worse. Poor oral hygiene has been linked to poor health elsewhere, including a higher risk of heart attack and cardiovascular disease.
Like fingerprints, everyone’s tongue is different. It’s the same with the assemblages of bacteria that call our mouths home. A recent microbial survey identified almost 400 different species in the mouths of 100 participants representing four different ethnic affiliations. Only 2 percent of the bacterial species were present in all of the individuals, albeit in different concentrations according to ethnicity. Eight percent were detected in 90 percent of the group. But most interestingly, said the researchers, each ethnic group – non-Hispanic blacks, whites, Chinese and Latinos – was identifiable by its own “signature” of shared microbes.