Print PageThe last century focused on bacterial agents associated with disease and neglected the human bacterial commensals. The microbial involvement in health and diseases is under a new scrutiny with the realization that the microbial genetic potential might be 10 times greater than the one of the human being carrying it. The Human Microbiome Project was created by the National Institutes of Health to answer some of the basic questions associated with organismal microbiology in a cohort of healthy adult subjects. Among the eighteen body sites selected and samples, seven were related to surfaces of the oral cavity and two of the oropharynx.
To investigate microbial composition and genetic potential two metagenomic approaches were used. Bacterial identification was performed using 454 pyrosequencing targeting the 16S rRNA. Metabolic and genetic potential of the microbiota was identified using Illumina-based shotgun sequencing. The raw data was processed through validated bioinformatics pipelines and made available for analysis. Additionally, LEfSe was used to identify biomarkers between body sites. The availability of over 200 healthy subjects presented unique opportunities to investigate normal microbial representation, diversity, and abundance.
Results/Conclusions
Comparative analysis of the nine oral sites phylogenetic composition indicated a predominance of Firmicutes phylum. The other major phyla includes Bacteroidetes, Proteobacteria, Fusobacteria and Actinobacteria. The relative abundance of some environmental phyla indicates that those are not transient bacteria and are part of the natural flora of healthy individuals. Streptococcus is the most represented genus in all oral sites, and might be the driver of future probiotic design for oral health.
The analysis of differentially represented genera among the nine oral sites indicated a novel subgrouping. The tooth, the only non-shedding surface of the digestive track shows a high level of similarity with the other sites. The oropharynx microbiota, represented by the throat and the palatine tonsils, is similar to the tongue microbiota. This novel subgrouping could be used to facilitate the monitoring of prospective cohort studies by using predictive reporter sites.
Shotgun sequencing of the microbiota sampled from three oral sites was performed. Differentially represented pathways and pathway penetrance were investigated using both KEGG and KEGG orthology. No major metabolic shift was observed. Pathways representation differed among each body sites and was associated in some instances with different membership levels of genera among the sites. The genetic potential of the microbiota associated with healthy subjects shows a similarity among body sites beyond the core functions.
