Hidden DNA Structures in the Mouth May Hold Keys to Health and Disease
Tokyo, Japan – in a groundbreaking discovery published in Nature Communications, researchers at the University of Tokyo have identified massive, previously undetected DNA structures within the oral microbiome. these genetic fragments,dubbed “Inocles,” appear to be crucial for bacterial adaptation to the challenging habitat of the human mouth,perhaps revolutionizing our understanding of oral health,disease prevention,and the broader field of microbiome research.
The human microbiome – the vast community of microorganisms inhabiting our bodies – has become a focal point of scientific examination. While the gut microbiome has received meaningful attention, the oral microbiome remains largely unexplored. This new research sheds light on a hidden layer of complexity within this ecosystem.
Inspired by recent findings of similar DNA fragments in soil bacteria, the Japanese team meticulously analyzed a large collection of saliva samples.They sought to determine if these “extra” genetic elements existed within the human oral cavity. Their efforts paid off with the identification of Inocles – substantial pieces of extrachromosomal DNA residing within bacterial cells, but distinct from the main bacterial chromosome.
“Many bacteria live in the oral cavity, but their functions are often a mystery,” explains Yuya Kiguchi, the lead researcher on the project. “It’s as if we’ve found a book with extensive footnotes – now we need to decipher their meaning.”
The discovery wasn’t easy. Customary DNA sequencing methods break DNA into smaller pieces, making it impractical to analyze these large structures. The team overcame this hurdle by employing advanced, long-read sequencing technologies, providing a comprehensive view of the bacterial genetic material.
A critical innovation was the development of a method, dubbed “prenuc,” to selectively remove human DNA from the saliva samples. This purification process yielded clearer and more precise bacterial DNA sequences for analysis. Using these techniques, researchers were able to fully assemble the genomes of Inocles found within Streptococcus salivarius, a common oral bacterium.
What makes Inocles particularly intriguing is their size. Averaging 35
