Ferreira Pilot Project Summary

The human microbiota is known as critical in protecting against infections, but little is known about how the skin microbiota performs its protective role. Members of the skin microbiome interact with other commensals as well as invading pathogens, and these interactions can be crucial to host protection. During these interactions, metabolites are produced and might play a role in how different species colonize the skin and cause infections. Our research group investigates the role of the skin microbiota in protecting against colonization and infection by pathogens by searching for, detecting, and identifying molecules that can affect the virulence of other species; in particular, biofilm production. Staphylococcus are one the most abundant genera on the human skin. Within this genus there are human pathogens, such as Staphylococcus aureus, and commensals, such as Staphylococcus epidermidis, both of which serve as models for uncovering the basic mechanisms of interactions between members of the skin microbiota. Our previous work showed that S. epidermidis produces molecules between 3 and 10KDa that strongly inhibit biofilm formation and disrupt
mature biofilms. The molecules were also able to reduce the antibiotic concentration required to eradicate biofilms. Planktonic growth was not affected, suggesting that these molecules have antivirulence activity. We also showed that the molecules produced by S. epidermidis modulate the expression of more than 800 genes in S. aureus biofilms, including several transcriptional regulators and virulence genes. In this project, we aim to better understand and characterize these molecules and the mechanisms by which S. epidermidis can affect S. aureus virulence. We propose to identify the antibiofilm molecules using solvent extraction,
fractionation, mass spectrometry and NMR analyses. We will also use bacterial genetics tools to identify genes responsible for production of the bioactive molecules by S. epidermidis as well as for the S. aureus response to the active compounds. Since there is a strong effect on overall virulence genes when S. aureus is grown in the presence of S. epidermidis metabolites, we will also evaluate the impact of these molecules on S. aureus adhesion and invasion of epithelial cells, as well as their effect on host immune responses to S. aureus.