Researchers have uncovered giant DNA inocles—massive extrachromosomal DNA elements—in bacteria living in the human mouth, a discovery that could reshape our understanding of oral health and immune function.
What Are Giant DNA Inocles?
Scientific teams at the University of Tokyo identified these large DNA structures, called inocles, within oral bacteria by using advanced long-read DNA sequencing techniques. Unlike typical bacterial plasmids, inocles are too large and complex to be detected by standard short-read sequencing methods. The term “inocle” stands for “insertion sequence encoded; oral origin; circle genomic structure.” These extrachromosomal elements exist outside the main bacterial chromosome and appear to carry genes that help bacteria adapt to the fluctuating environment of the mouth.
Prevalence and Potential Health Implications
Analysis of saliva samples from hundreds of volunteers revealed that approximately 74% of people carry these inocles as part of their oral microbiome. The research also found correlations between inocle levels and variations in immune system function, including responses to bacterial and viral infections. This suggests that inocles may play a role in modulating oral immunity and potentially influence susceptibility to diseases such as gum disease and even cancer.
Researchers liken discovering inocles to finding “a book with extra footnotes stapled to it,” highlighting how much remains unknown about the functions of these DNA elements. Ongoing studies aim to decode their genetic content and understand how they help bacteria survive oxidative stress, DNA damage, and other challenges inside the oral cavity.
This discovery opens new avenues for microbiome research and could lead to novel approaches in diagnosing and treating oral diseases by targeting the bacterial communities influenced by inocles.