The reconstruction of the oral microflora over 100,000 years of human history may have revealed a surprising change in the bacteria that inhabit our mouths.
Researchers from Germany and the US have teamed up to identify DNA extracted from human teeth and Neanderthal bats, using protein synthesis techniques used by bacteria.
It is an important time in the study of microbes that live in humans, which gives us information about bacteria that are no longer part of our body’s natural environment. In the future, these results can also be used to develop new drugs.
Tartar, or calcified dental plaque, is a perfect hiding place for pathogens, which is why your dentist emphasizes the importance of brushing and flossing every day. Despite its effectiveness in protecting bacteria, the researchers only extracted tiny bits of DNA from ancient samples to use. This left the task of scientific research to understand what happened.
Christina Warinner, an anthropologist at Harvard University in Massachusetts, said: “There are about 3 million species of bacteria, but we usually find ancient DNA that is only 30 to 50 years old.”
“In other words, each ancient bacterial genome is like a 60,000-piece jigsaw puzzle, and each piece of tooth tartar contains millions of genomes.”
The researchers started with records from 12 Neanderthals (between 40,000 and 102,000 years old) and 34 humans (between 150 and 30,000 years old).
In the past, fragments of such genes could be compared to the genomes of modern insect species – useful information, but one that will not reveal new or extinct species.
In this case, the researchers developed a technique known as the de novo assembly technique, where small pieces of DNA can be assembled into a whole genome.
It’s like trying to put together a jigsaw with only the other pieces, and no picture to work with. Various techniques, including fusion detection and characterization, are put in place to try to fill in the gaps – and after three years of careful comparison and analysis of all samples, the bacterial genome can be reconstructed.
From the known species, the researchers discovered a series known as biosynthetic gene clusters. The genes within these groups play an important role in the production of proteins within the bacteria.
“This is how bacteria make complex and effective drugs,” he says Warner. “Almost all of our antibiotics and most of the drugs we use end up being derived from biosynthetic bacterial species.”
Transferring the recombinant DNA systems into modern bacteria, the researchers successfully engineered enzymes that mimicked the ancient blueprints of our ancestors’ oral bacteria. One of these enzymes produced organic molecules called furans, which today works by showing between bacterial cells.
Based on genetic studies on both sides of the enzyme that produces furan, the researchers hypothesize that this gene may play a role in the regulation of bacterial photosynthesis.
On the whole, the highest number of movements seems to be of the type of bacteria called Chlorobium. Able to use light to convert sulfur into energy, these microbes are not what we expect to be fighting against our teeth.
It is possible that they used to live in the mouth of a person, soaking up the small rays that caused our nerves to burn when we opened our mouths. Or it was the result of drinking pool water.
Although we are not talking about bringing viruses back to life here – the bacteria kind Jurassic Park – ancient genomes are useful in telling scientists how our microbiome has changed and evolved over thousands of years.
For example, there is the question of why these bacteria are no longer in our mouths – perhaps due to changes in behavior or diet – which future research can look into.
“Now we can scale this up,” says Warinner. “Suddenly, we can expand our understanding of the biochemical past.”
Research has been published in Science.
