The stress hormone cortisol induces virulence in the oral microbiome

The human microbiome maintains under normal conditions a state of homeostasis. Disruption of homeostasis also referred to as dysbiosis, has been shown to be causally linked to the development of a variety of host diseases. These dysbiotic microbial communities exhibit synergistic interactions for enhanced protection from host defenses, nutrient acquisition, and persistence in an inflammatory environment. 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 its environment thus changing its expression gene profile to fit the needs of the new environment. Cortisol or hydrocortisone is the primary hormone responsible for the stress response, and its levels increase in saliva and serum with the severity of periodontal disease. Most studies have focused on the effect of hormones on growth or virulence of individual organisms. 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.