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Investigating the Progression of Pathogenic Germs and Ailments in the Historical Mouth Bacterial Community

Rich and complex assortment of oral microbes, composed of a myriad of bacterial species, micro-eukaryotes, archaea, and viruses, forms the human oral microbiota's intricate ecosystem.

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Vast assortment of life forms populate the human mouth, encompassing a multitude of bacterial...
Vast assortment of life forms populate the human mouth, encompassing a multitude of bacterial species, plus microeukaryotes, archaea, and viruses, with their intricate ecosystem maintaining a delicate balance.

Investigating the Progression of Pathogenic Germs and Ailments in the Historical Mouth Bacterial Community

Oral pathogens have undergone evolutionary changes since the Bronze Age, a study reveals.

The analysis of 4,000-year-old teeth, conducted by an international team of researchers, sheds light on the evolution of oral pathogens over millennia and the factors that contributed to these changes. The findings, published in the journal Molecular Biology and Evolution, reveal significant shifts in oral microbial communities and the adaptive responses of pathogens to changes in the human host's environment.

Professor José Ramón Alonso Penña, cell biology expert at the University of Salamanca, explains that the human oral cavity is home to a diverse and complex microbiota, interacting with the host's immune system. The study reveals important changes in the oral microenvironment from the Bronze Age to the present day.

Iseult Jackson and her colleagues, from Trinity College Dublin, Atlantic Technological University, and the University of Edinburgh, recovered remarkably preserved microbiomes from two 4,000-year-old teeth belonging to the same male individual found in an Irish limestone cave. Genetic analyses of these microbiomes reveal the presence of bacteria associated with gum disease.

The researchers identified an exceptionally rare finding—the first high-quality ancient genome of Streptococcus mutans, a renowned cause of dental caries. Although common in contemporary mouths, S. mutans is extremely scarce in the ancient genomic record, mainly due to its acidogenic nature. This acid degrades DNA and prevents plaque mineralization, making it difficult to recover ancient samples of this bacterium.

The team also found evidence to support the "disappearing microbiome" hypothesis, which posits a loss of biodiversity in modern microbiomes compared to their ancestors. The two Bronze Age teeth contained highly divergent strains of Tannerella forsythia, a gum disease-causing bacterium, with genetic differences more pronounced than any pair of modern strains. This loss of diversity is a cause for concern, as it may impact human health.

The study also reveals the rapid expansion of T. forsythia populations starting around 600 years ago, likely due to changes in host demographics and population size, as well as an increase in virulence factors. This expansion resulted in a single dominant lineage worldwide.

Researchers also observed significant changes in the abundance and distribution of oral pathogens across time, with S. mutans showing a marked increase in modern populations. These findings highlight the profound impact of dietary changes, such as the introduction of sugary foods, on the evolution and prevalence of oral pathogens.

The study's authors stress the need for further research to better understand the loss of microbial diversity and the implications it may have on human health.

Sources:

  1. Jackson I, Woodman P, Dowd M, Fibiger L, Cassidy LM (2024) Ancient Genomes From Bronze Age Remains Reveal Deep Diversity and Recent Adaptive Episodes for Human Oral Pathobionts Molecular Biology and Evolution doi: 10.1093/molbev/msae017
  2. Trinity College Dublin. Scientists extract genetic secrets from 4,000-year-old teeth to illuminate the impact of changing human diets over the centuries. ScienceDaily. ScienceDaily, 27 March 2024.
  3. This content was originally published by Mapping Ignorance, 04.18.2024, under the terms of a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International license.

The study published in Molecular Biology and Evolution reveals significant shifts in the oral microbial communities over millennia, including bacteria associated with medical-conditions like gum disease. The findings also highlight the profound impact of nutrition and dietary changes, particularly the introduction of sugary foods, on the evolution and prevalence of oral pathogens.

Researchers observed a loss of diversity in the oral microbiome from the Bronze Age to the present day, with implications for health-and-wellness and fitness-and-exercise. The study's authors stress the need for further research to better understand this loss of diversity and its potential consequences.

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