Oral Bacteria Create a ‘Fingerprint’ in Your Mouth

Emily Caldwell, Medical Xpress, October 23, 2013

The bacteria in the human mouth–particularly those nestled under the gums–are as powerful as a fingerprint at identifying a person’s ethnicity, new research shows.

Scientists identified a total of almost 400 different species of microbes in the mouths of 100 study participants belonging to four ethnic affiliations: non-Hispanic blacks, whites, Chinese and Latinos.

Only 2 percent of bacterial species were present in all individuals–but in different concentrations according to ethnicity–and 8 percent were detected in 90 percent of the participants. Beyond that, researchers found that each ethnic group in the study was represented by a “signature” of shared microbial communities.

“This is the first time it has been shown that ethnicity is a huge component in determining what you carry in your mouth. We know that our food and oral hygiene habits determine what bacteria can survive and thrive in our mouths, which is why your dentist stresses brushing and flossing. Can your genetic makeup play a similar role? The answer seems to be yes, it can,” said Purnima Kumar, associate professor of periodontology at The Ohio State University and senior author of the study.

“No two people were exactly alike. That’s truly a fingerprint.”

Kumar used a DNA deep sequencing methodology to obtain an unprecedented in-depth view of these microbial communities in their natural setting.

When the scientists trained a machine to classify each assortment of microbes from under the gums according to ethnicity, a given bacterial community predicted an individual’s ethnicity with 62 percent accuracy. The classifier identified African Americans according to their microbial signature correctly 100 percent of the time.

The findings could help explain why people in some ethnic groups, especially African Americans and Latinos, are more susceptible than others to develop gum disease. The research also confirms that one type of dental treatment is not appropriate for all, and could contribute to a more personalized approach to care of the mouth.

“The most important point of this paper is discovering that ethnicity-specific oral microbial communities may predispose individuals to future disease,” Kumar said. Though it’s too soon to change dental practice based on this work, she said the findings show that “there is huge potential to develop chair-side tools to determine a patient’s susceptibility to disease.”

The research is published in the Oct 23, 2013, issue of the journal PLOS ONE.


Using only the bacteria found under the gums–which are called subgingival microbes–the classifying machine performed best at positively identifying African Americans according to their microbial communities, followed by positive identifications of Latinos at 67 percent and Caucasians at 50 percent–but with 91 percent specificity, meaning the classifier determined how often a sample did not come from a white person 91 percent of the time.

Kumar and colleagues then expanded the selection of total microbes in all areas of the mouth, and identified surrogate communities of bacteria that were present in at least 80 percent of participants of each ethnic group. These communities showed a prediction likelihood of 65 percent for African Americans, 45 percent for Caucasians, 33 percent for Chinese and 47 percent for Latinos.

“Nature appears to win over nurture in shaping these communities,” Kumar noted, because African Americans and whites had distinct microbial signatures despite sharing environmental exposures to nutrition and lifestyle over several generations.


It did make sense to Kumar that bacteria below the gums are most closely linked to ethnicity identification because they are the least likely to be disrupted by environmental changes in the mouth, such as food, toothpaste and tobacco.


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  • Manaphy

    Typical uneducated Liberal response to this article: “That’s not true! My university proffesor taught me that ALL RACES ARE EQUAL!!!!!!!!”

    The reality is that race is more than just a skin pigmentation. Race determines your DNA, your behavior, your IQ, your role in society, etc.. Race is who you are.

    • Oom Paul

      We all bleed red!

      • Oom Paul

        but ‘white girl bleed a lot’ more though…

      • Spartacus

        Rats bleed red too…

    • A Freespeechzone

      Hmmmm….equal they say? Look at Africa…a continent with more raw resources than almost anyplace on Earth… It’s mostly run by blacks and it’s a crap hole by ANY definition.

      All races and their abilities are NOT EQUAL and never will be–even under affirmative action.

      No apologies

    • Jefferson

      There are even differences in I.Q between different sub races of the same racial group.

      There are Caucasoid countries where the average I.Q is in the double digits and not the triple digits.

      For example, Armenians on average have lower intelligence than Austrians.

      • M.

        I heard that ethnic Armenians have a lot of Mongoloid blood. So not a good example there.

        • Sangraal

          I would’ve thought they’re more Turkic than Mongoloid. They’re Caucasian, but I wouldn’t consider them ‘white’.

          • Sick of it

            Turkic tribes, after a certain point, had Mongoloid blood in them due to interactions, conquests, etc. on the part of Mongoloid tribes. They may have originally been white, that’s a debate all by itself, but certainly they are part Mongoloid today. Look at Central Asian peoples today.

      • Formerly_Known_as_Whiteplight

        As IQ is tested, there are 13 separate categories. I have often wondered why just 13? It has always seemed to me that one measure of intelligence has to be the ability to quickly adapt to new situations/environments. (I mean in the McGiver sense, an ability to survive when presented with an unfamiliar situation/problem. Some people with very high IQs couldn’t survive for a minute without their well set up environments.

    • Rhialto

      The Liberals readily concede physical inequities of races. What the Liberals maintain is that all races are brain equal, that is intellectually and behaviorally. I am always mindful of this when discussing race with Liberals.

      • Brian

        Libs only believe in evolution from the neck down.

  • Oil Can Harry

    ” …some ethnic groups, especially African-Americans and Latinos, are more susceptible than others to develop gum disease…”

    Dass why me an’ mah homies don’t eat Wrigley’s or Bazooka. Da gum might have a disease in it.

  • Tim_in_Indiana

    Wow, bacteria follow “social constructs!” Who’da thunk it?

  • JohnEngelman

    The bacteria discriminate by race.

    • rightrightright

      The bacteria need some re-education and sensitivity training.

      • Franklin_Ryckaert

        Not necessary, they are a social construct anyway. So we can safely ignore them.

      • Brian

        Especially the Klanmanella and trichignomesain strains.

    • Bossman

      I’ve also heard and read that Blacks have the whitest and strongest teeth which grows longest into the gum. If they have more gum disease, it could be a function of poverty and ignorance of oral hygiene.

  • Spartacus

    Race is just a social construct. This “Kumar” person is obviously a naziwhowantstokillsixmillionjews , and as such he should be fired, and a lesbian should pinch his nipples, as true Enlightenment demands .

  • IstvanIN

    Why do we need Purina Kumar as a professor anyway?

  • JDInSanD

    “One type of dental treatment is not appropriate for all” so cancel the space shuttle program and get to work whitey. Use all your scientific talent to find a way to stop gum disease in blacks and hispanics without requiring them to brush, floss and stop eating junk food because they’re not going to get around to it anytime soon.

    “Nature appears to win over nurture in shaping these communities,” Wow, was referring to their neighborhoods or their mouth bacteria?

    • 1stworlder

      They just didn’t want to say that brushing their teeth was too much like work for blacks & browns.

      • Brian

        Clearly we need affirmative chemical reaction, with subsidies for Afroengineered mouthwash. ‘Blacksterine’.

        • I would recommend either antimony pentafluoride or lithium diisopropyl amide. These would be uniquely suited to them.

          • Brian

            I knew you would have a solution. Come to think of it, ‘antimony’ sounds rather like an Ebonics name.

  • Viking_61

    Bacteria bees raciss.

  • I’m offended that the SPLC hasn’t added mouth bacteria to their Hate Watch list by now.

  • 1stworlder

    Could it be that blacks got identified 100% because brushing their teeth is too much like work? Perhaps fried chicken tastes differently to them.

  • Mahound

    But … but … only skin color is different. Deep down we’re all the same …

    • Katherine McChesney

      *moan* I hope you are joking. As:


  • M.

    “Ethnicity”… pff what kind of PC crap is that? Just call it “race” already!

    • Sick of it

      Different ethnic groups exist within each race as well as between the races (mixed peoples). The term race itself once referred to distinct ethnic groups, not a larger conglomerate group.

  • John R

    I find it most interesting that the study said that it was easiest to identify “African Americans” (i.e. Negroes) from analysis of the material in their gums. It was hardest to identify the “Caucasian” (uh, Whites of European descent) samples. Well, HECK! (I didn’t curse, dear moderator, see?), even a CHILD could have predicted that! We Whites are the most diverse race on the planet. We are a mixture of many different peoples, from many different tribal origins. This is in sharp contrast to what the “experts” have been saying for years that Africans had the most variety. You can TELL the difference between an Englishman, a German, a Swede, a Russian, an Italian, etc. But the blacks are indeed “all alike.”

    • Bossman

      Blacks are the oldest race. Whites are the most mongrelized race.

      • Katherine McChesney

        No proof of that. Read “Not Out of Africa”.

    • Brian

      Africans do have the most genetic diversity, and whites less, but whites have more cultural diversity. Besides, most black Americans are from a specific region of West Africa and wouldn’t have the full gamut of genetic diversity that you might find in San, pygmies, Ethiopians, Nigerians, etc. All we get is the Ghana/Liberia/Togo/Benin subgroup.

  • QuinnTheEskimo9

    A forensic scientist can already determine the race of an individual from DNA, bone density and structure and shape of the skull (blacks have smaller frontal lobes and a smaller cranial capacity.
    This is done all the time to determine the race of murderers, etc., the information is not released lest the scientist be accused of racism. To keep his job he has to say that there are no differences between the races down to the atomic level as he identifies criminals and victims by race through DNA, etc.

    • Brian

      Black Americans are more likely to be dolichocephalic (immediately sloping forehead), have different position in the gonion (lower jawbone angle), have mandibular prognathism (making the lips protrude past the tip of the nose), and have a wider ocular orbit distance (look at how far apart Jesse Jackson’s eyes are…looks a little like a Admiral Ackbar or a hammerhead shark). Blacks generally have a higher waist– longer legs, shorter torso for the same height.

      • Bossman

        There are indeed many physical differences between the races. Some of those differences confer real advantages and some not. Blacks do have whiter, stronger and bigger teeth than whites.

  • Franklin_Ryckaert

    The Party will need a Ministry of DoubleThink to “harmonize” scientific discoveries with the Official Ideology.

  • Brian

    The classifier identified African Americans according to their microbial signature correctly 100 percent of the time.

    Does this include sniffing the aroma in an elevator downtown? I’ve heard blacks say that we smell like wet dogs too.

  • Brian

    “Nature appears to win over nurture in shaping these communities,” Kumar noted

    Truer words have rarely been spoken.

  • Brian

    The devolved branch in Detroit is ‘homo defectus’.

  • Katherine McChesney

    Why would you want to get that close to them?

  • Formerly_Known_as_Whiteplight

    NOT “in fact,” I’m afraid you’re fantasizing. Different species cannot interbreed. However, actual new evidence suggests that in the future, race mixing could result in the development of species that would not be able to interbreed. This is because it is isolated same groups that produce the most mutations that lead to genetic advancement and mixing generalizes human dna actually greatly reduces the number of those mutations to eventually none. Groups that remained the most isolated and unmixed would constitute one species. (ref; Before the Dawn).

    Another possibility of new human species is the possibility that two classes of humans would also emerge due to the manipulation “augmentation” of genes. We could soon have two classes; those who have augmented dna and those that don’t. (ref; The Futurists)