Did you know our saliva contains bacteria? We knew saliva contains electrolytes, mucus, enzymes for digestion and antibacterial compounds, but what many of us are unaware of, is the presence of bacteria in the secretion inside our mouth.
Scientists have recently compiled the first comprehensive list of the salivary microbiome – the bacterial cells present in the saliva, across Indian populations. This research was published in the journal Plos One.
Our bodies carry as many bacterial cells as the number of human cells in the body. These comprise of both the ‘good’-health promoting and the ‘bad’-disease causing bacteria. The type of bacteria varies depending upon the location on the body. Identifying these is important for understanding the balance between health and disease and the genetic diversity among populations.
Researchers in India in close collaboration with their peer in Germany analyzed saliva from 92 healthy volunteers. They took salivary samples from 3 different regions of the country- North (Jammu & Kashmir and Uttarakhand), East (Jharkhand, West Bengal, and Assam) and South (Andhra Pradesh, Tamil Nadu, and Telangana), representing a total of 8 different states for the analysis. Applying a well-accepted approach to sequence the 16S rRNA gene- a marker region of the bacterial genome, they identified 165 bacterial genera and 785 unique OTUs (Operational Taxonomic Units), a commonly used unit of microbial diversity in order to group together closely related microorganisms.
Dr. Stoneking of the Max Planck Institute for Evolutionary Anthropology, Germany, points out, “Traditionally, such studies have been carried out in populations from Europe or the US; there is tremendous diversity in the saliva microbiome of Indian populations that is not at all present in European/US populations”. He is a co-corresponding author of the study.
The study found certain OTUs that have not been previously reported in the repertoire and are unique to the Indian population, namely, Solobacterium spp., Lachnoanaerobaculum spp. and Alloprevotella spp. 9 new bacterial genera not listed in Human Oral Microbiome Database (HOMD) were also identified.
Dr. Stoneking explains that a person’s susceptibility to disease is dependent to a large extent on their body’s microbial composition. Thus, it becomes critical to have a baseline database of the unique microbiome of different populations for future studies.
Dr. Reddy emphasizes that there is immense bacterial richness in salivary microbiome in Indian populations. He adds, “The degree to which the differential distribution of oral microbiome might contribute to different patterns of disease across Indian populations could be an important focus of further studies and given the extraordinary genetic and cultural diversity of Indian populations, the Indian subcontinent is a natural laboratory for further such investigations”. Dr. Reddy, Head of Lab of Genomics and Profiling Applications at Centre for DNA Fingerprinting and Diagnostics (CDFD), Hyderabad is a co-corresponding author of the study.
The research was performed by Anujit Sarkar, Dr. Mark Stoneking, and Dr. N Madhusudan Reddy. This study was funded as part of the Max Planck Partner Group Programme to MRN from the Department of Science and Technology, Government of India and the Max Planck Society, Germany.
All datasets generated in this study are freely available under the project ‘Human salivary microbiome diversity in India’ uploaded to Figshare Salivary Microbiome Data.
