The effect of the stress hormone cortisol on the metatranscriptome of the oral microbiome.

Imbalances of the microbiome, also referred to as microbial dysbiosis, could lead to a series of different diseases. One factor that has been shown to lead to dysbiosis of the microbiome is exposure to psychological stressors. Throughout evolution microorganisms of the human microbiome have developed systems for sensing host-associated signals such as hormones associated with those stressors, enabling them to recognize essential changes in their environment, thus changing their expression gene profile to fit the needs of the new environment. The most widely accepted theory explaining the ability of hormones to affect the outcome of an infection involves the suppression of the immune system. Commensal microbiota is involved in stressor-induced immunomodulation, but other biological effects are not yet known. Here we present the impact that cortisol had on the community-wide transcriptome of the oral community. We used a metatranscriptomic approach to obtain first insights into the metabolic changes induced by this stress hormone as well as which members of the oral microbiome respond to the presence of cortisol in the environment. Our findings show that the stress hormone cortisol directly induces shifts in the gene expression profiles of the oral microbiome that reproduce results found in the profiles of expression of periodontal disease and its progression.