Researchers at the University of Tokyo have discovered a previously unknown genetic element in the human mouth, called Inocles. This discovery, part of their study of the human oral microbiome, may impact oral health, immunity, and cancer risk.
A team led by Yuya Kiguchi analyzed saliva samples from the university’s cutting-edge laboratory to identify hidden DNA elements.
They discovered Inocles, a type of extrachromosomal DNA that exists within bacterial cells but independently of their primary DNA. These DNA fragments, like extranotes in a book, may help bacteria adapt to the changing oral environment.
Identifying Inocles is challenging due to the limitations of traditional DNA sequencing methods, which typically break genetic material into small fragments.
To overcome this issue, the team employed advanced long-read sequencing technology, which can assemble larger DNA fragments.
They also developed a technology called preNuc that selectively removes human DNA, thereby improving the accuracy of sequencing other DNA fragments.
The team discovered that the host of Inocles is Streptococcus salivarius, a bacterium commonly found in the mouth. With a genome size of 350 kilobase pairs, Inocles is one of the largest extrachromosomal elements in the human microbiome.
Genes within Inocles are involved in antioxidative stress responses, DNA repair, and cell wall adaptation to external stress, potentially contributing to oral health and disease prevention.
Going forward, the researchers aim to develop methods to culture bacteria carrying Inocles to further investigate their role in oral health, including their potential impact on tooth decay, gum disease, and even cancer.
Early indications suggest that Inocles may serve as markers for serious diseases, making them an important avenue for future research.
The research team estimates that nearly 74% of humans carry Inocles, marking a major breakthrough in microbiome research, which has long been hampered by technical limitations.
Now that Inocles has been identified, the research team is working to understand its impact on human health and the oral microbiome.
