Up to 80 million bacteria sealed with a kiss

Couple about to kiss (stock image). As many as 80 million bacteria are transferred during a 10 second kiss, according to research published in the open access journal Microbiome.

As many as 80 million bacteria are transferred during a 10 second kiss, according to research published in the open access journal Microbiome. The study also found that partners who kiss each other at least nine times a day share similar communities of oral bacteria.

The ecosystem of more than 100 trillion microorganisms that live in our bodies -- the microbiome -- is essential for the digestion of food, synthesizing nutrients, and preventing disease. It is shaped by genetics, diet, and age, but also the individuals with whom we interact. With the mouth playing host to more than 700 varieties of bacteria, the oral microbiota also appear to be influenced by those closest to us.

Researchers from Micropia and TNO in the Netherlands studied 21 couples, asking them to fill out questionnaires on their kissing behaviour including their average intimate kiss frequency. They then took swab samples to investigate the composition of their oral microbiota on the tongue and in their saliva.

The results showed that when couples intimately kiss at relatively high frequencies their salivary microbiota become similar. On average it was found that at least nine intimate kisses per day led to couples having significantly shared salivary microbiota.

Lead author Remco Kort, from TNO's Microbiology and Systems Biology department and adviser to the Micropia museum of microbes, said: "Intimate kissing involving full tongue contact and saliva exchange appears to be a courtship behavior unique to humans and is common in over 90% of known cultures. Interestingly, the current explanations for the function of intimate kissing in humans include an important role for the microbiota present in the oral cavity, although to our knowledge, the exact effects of intimate kissing on the oral microbiota have never been studied. We wanted to find out the extent to which partners share their oral microbiota, and it turns out, the more a couple kiss, the more similar they are."

In a controlled kissing experiment to quantify the transfer of bacteria, a member of each of the couples had a probiotic drink containing specific varieties of bacteria including Lactobacillus and Bifidobacteria. After an intimate kiss, the researchers found that the quantity of probiotic bacteria in the receiver's saliva rose threefold, and calculated that in total 80 million bacteria would have been transferred during a 10 second kiss.

The study also suggests an important role for other mechanisms that select oral microbiota, resulting from a shared lifestyle, dietary and personal care habits, and this is especially the case for microbiota on the tongue. The researchers found that while tongue microbiota were more similar among partners than unrelated individuals, their similarity did not change with more frequent kissing, in contrast to the findings on the saliva microbiota.

Commenting on the kissing questionnaire results, the researchers say that an interesting but separate finding was that 74% of the men reported higher intimate kiss frequencies than the women of the same couple. This resulted in a reported average of ten kisses per day from the males, twice that of the female reported average of five per day.

To calculate the number of bacteria transferred in a kiss, the authors relied on average transfer values and a number of assumptions related to bacterial transfer, the kiss contact surface, and the value for average saliva volume.

Source: BioMed Central

Read More

Lead in teeth can tell a body's tale, study finds

Revealing information UF geology professor George Kamenov has published research that shows trace amounts of lead in modern and historical human teeth can give clues about where they came from. Credit: Ray Carson/UF Photography

Your teeth can tell stories about you, and not just that you always forget to floss.

A study led by University of Florida geology researcher George D. Kamenov showed that trace amounts of lead in modern and historical human teeth can give clues about where they came from. The paper will be published in the August issue of Science of The Total Environment.

The discovery could help police solve cold cases, Kamenov said. For instance, if an unidentified decomposed body is found, testing the lead in the teeth could immediately help focus the investigation on a certain geographic area. That way, law enforcement can avoid wasting resources checking for missing persons in the wrong places.

"We can use this pollution signal to figure out where these people came from," he said.
Lead is composed of four variants, called isotopes. The amount of those isotopes fluctuates in different rocks, soils and ores -- and, therefore, regions of the world.

Mining and other pollution-causing activities release that lead into the environment, and it accumulates in children's bodies as they grow because kids inhale dust and ingest soil when they put their hands in their mouths.

Tooth enamel, which develops during childhood, locks in the lead signals and preserves them.
"When you grow up, you record the signal of the local environment," Kamenov said. "If you move somewhere else, your isotope will be distinct from the local population."
Even different teeth can reveal certain facts.

First molar enamel is finished forming by age 3, so it provides information about birth and toddler years. Incisor and canine enamel starts later and finishes around age 5, so it gives insight into early childhood. The third molar enamel does not start forming until age 8, so it indicates late childhood residences.

Lead analysis can also tell what time period a body is from.

Modern and historical teeth have different signals, according to the study. The natural composition of lead changed over the past century because of mining and the use of leaded gasoline, so there's a clear distinction between modern and historical human exposure.

Using that information, archaeologists can identify early European bodies in New World areas.
"You can go back in time, look at archaeological sites and try to reconstruct human migration," Kamenov said.

But modern American teeth are like no others in the world, according to the study. Whereas available data for areas such as South America overlap with Europe, American teeth can be identified anywhere due to usage of ores with distinct isotope signals in the United States.
"What's in the environment goes into your body," Kamenov said

Source: University of Florida.

Read More