This project aims to investigate diversity and community structure, identify novel and constitutively present species, and analyze the functional role of the virtually uncharacterized ocular surface microbiome. Successful completion will provide the first guidance to the uncharted territories of ocular microbial ecology, allow detecting of the previously untraceable bacteria, and study host-microbiome interactions.

This project has high relevance to human health, since in the majority of cases of ocular surface (OS) infections and acute inflammation the disease-causing pathogen remains unidentified. One explanation is the presence of new, previously uncharacterized pathogens on the OS. In support of this notion, recent evidence that a diverse commensal microbiota (the microbiome) colonize healthy OS started to accumulate. How abundant and diverse are the indigenous OS microbiota, what role does the microbiome play in the OS health and disease and how does it avoid the host immune surveillance? Conventional microbiology cannot be used to address these questions because most microbes resist growing in culture. Our experiments demonstrated that as many as 300 different bacterial phylotypes are present on the human conjunctiva, which is four times more than previously identified in culture. These include representatives of 24 bacterial genera have never been detected on the OS before and dozens of unknown species.

More intriguingly, in our experiments we detected high bacterial load on healthy, culture-negative corneal epithelium. These data and our results obtained in the conjunctiva allow us to hypothesize that the uncultivable microbial community colonizing the human cornea is unique in structure. The high abundance of corneal microbiota implies that it is essential for the homeostasis of this vital for sight tissue. To test this hypothesis we will utilize culture-independent approach, the next-generation 454 sequencing technology to define the community structure, diversity and identify core bacterial species present on corneas of all individuals.