A new study made use of the dental plaque of modern and ancient humans to delve deeper into the oral microbiome.
Oral Microbiome
Each individual has an oral microbiome, which is a group of hundreds of microorganisms that fill the mouth. This oral microbiome is bound to be diverse and large, with hundreds of varying microorganism species at any particular time. It also varies depending on the environment in which a person lives.
Live Science reports that in order to dig deeper into the prehistoric oral microbiome, biomolecular archaeologist Christina Warinner from Harvard University used some novel methods to examine ancient dental plaque that had already solidified into calculus or tartar.
Warinner explains to Live Science that dental calculus is the only body part that routinely fossilizes even when one still lives. Live Science also adds that across an entire ancient skeleton, dental calculus also contains the highest ancient DNA concentration.
With as little as a few milligrams of dental calculus, Warinner was able to isolate billions of DNA short fragments from a variety of hundreds of species. The fragments could then be consolidated in order to pinpoint the species.
According to Genetic Engineering and Biotechnology News, Warinner explains that through the study, the researchers were able to reach a major milestone in demonstrating the great chemical and genetic diversity of humans' microbial history. Their findings were detailed in the Science journal.
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Bacteria Trapped in Ancient Neanderthal Teeth
According to Live Science, examining the ancient dental plaque came with an additional challenge, as the DNA found within the calculus could have been from already-extinct microbes.
Throughout the study, the team looked into 12 ancient Neanderthals' dental calculus, as well as that of 18 contemporary humans from 100,000 years ago and 34 archaeological humans. Over 10 billion fragments of DNA were sequenced and reassembled to form 459 different bacterial genomes. Around 75% of these are mapped to known bacteria.
Doing so enabled the scientists to pinpoint two specific species that belong to the Chlorobium bacteria genus. These were observed in seven individuals in the study who were from the Upper Pleistocene era. This bacterial species did not match any known ones but was associated with C. limicola.
Live Science adds that such bacterial species were nearly fully absent from the dental calculus of those who lived within the last 10,000 years. From the Upper Pleistocene up to the Holocene period, which spanned roughly 100,000 years, humans dwelt in caves, raised animals, and came up with innovative plastics. All of these have unique bacterial colonies of their own. Chlorobium frequency changes appeared to align with the lifestyle changes of human ancestors.
In the present, the oral microbiome of humans is gravely different, as toothbrushing has now kept oral bacteria at minimal levels.
The team also looked into biosynthetic gene clusters (BGC) in order to examine the exact enzymes produced by the Chlorobium species. By understanding these BGs, scientists could come up with novel antibiotic treatments.
They observed that the Chlorobium BGCs came up with two new enzymes when they were inserted into bacteria that were alive. These enzymes may play a crucial role when it comes to photosynthesis. Warinner notes that these techniques could lead to novel antibiotics one day.
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