Abstract
The taxonomic composition of the salivary microbiota has been reported to differentiate between oral health and disease. However, information on bacterial activity and gene expression of the salivary microbiota is limited. The purpose of this study was to perform metagenomic and metatranscriptomic characterization of the salivary microbiota and test the hypothesis that salivary microbial presence and activity could be an indicator of the oral health status. Stimulated saliva samples were collected from 30 individuals (periodontitis: n = 10, dental caries: n = 10, oral health: n = 10). Salivary microbiota was characterized using metagenomics and metatranscriptomics in order to compare community composition and the gene expression between the three groups. Streptococcus was the predominant bacterial genus constituting approx. 25 and 50% of all DNA and RNA reads, respectively. A significant disease-associated higher relative abundance of traditional periodontal pathogens such as Porphyromonas gingivalis and Filifactor alocis and salivary microbial activity of F. alocis was associated with periodontitis. Significantly higher relative abundance of caries-associated bacteria such as Streptococcus mutans and Lactobacillus fermentum was identified in saliva from patients with dental caries. Multiple genes involved in carbohydrate metabolism were significantly more expressed in healthy controls compared to periodontitis patients. Using metagenomics and metatranscriptomics we show that relative abundance of specific oral bacterial species and bacterial gene expression in saliva associates with periodontitis and dental caries. Further longitudinal studies are warranted to evaluate if screening of salivary microbial activity of specific oral bacterial species and metabolic gene expression can identify periodontitis and dental caries at preclinical stages.
Highlights
Periodontitis and dental caries are the two most prevalent oral diseases and the primary causes of tooth loss in the western world.[1,2] At present, periodontitis and dental caries are mostly diagnosed at late stages of disease, often leading to costly and invasive dental treatment
A significantly higher α-diversity was recorded by metagenomics compared to metatranscriptomic analysis (Figs. 1a–b) (p < 0.05)
No difference in α-diversity was observed between groups using either salivary microbiomes were dominated by formate C-acetyltransferase, enolase, 5-methyltetrahydropteroyltriglutamate--homocysteine methyltransferase, and pyruvate oxidase (Supporting material Fig S2A)
Summary
Periodontitis and dental caries are the two most prevalent oral diseases and the primary causes of tooth loss in the western world.[1,2] At present, periodontitis and dental caries are mostly diagnosed at late stages of disease, often leading to costly and invasive dental treatment. The oral cavity harbors a diverse microbiota comprising more than 700 unique bacterial species.[3] The microbiota plays a pivotal role in maintenance of oral homeostasis, as various oral habitats are colonized by characteristic bacterial community profiles organized in local biofilms.[4] ecological changes, for example in relation to increased sugar intake, insufficiently performed oral hygiene or fluctuations in the immune response can induce structural[5,6,7] and functional alterations[8,9,10] of local oral biofilms Such alterations may in turn change the relation between the host and the resident microbiota from symbiosis to dysbiosis, thereby fueling initiation and progression of periodontitis and dental caries
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