Raphael H. Valdivia
Professor of Molecular Genetics and Microbiology

My laboratory is interested in how microbes influence human health, both in the context of host-pathogen and host-commensal interactions.  For many pathogens, and certainly for most commensal microbes, the molecular basis of how host and microbial factors contribute to a beneficial outcome for us, is poorly understood. We currently focus on two experimental systems:

Chlamydia trachomatis infections are responsible for the bulk of sexually transmitted bacterial diseases and are the leading cause of infectious blindness (trachoma) in the world. Chlamydia  resides within a membrane bound compartment (“inclusion”). From this location, the pathogen manipulates the cytoskeleton, inhibits lysosomal recognition of the inclusion, activates signaling pathways, re-routes lipid transport, and prevents the onset of programmed cell death. Remarkably, all of these functions are achieved with a genome that encodes < 900 proteins, indicating that the Chlamydia genome is streamlined for intracellular survival.

Our laboratory focuses on identifying and characterizing the bacterial factors that are secreted into the host cell cytoplasm to manipulate eukaryotic cellular functions. We use a combination of cell biological techniques, biochemistry, genetics, genomics, proteomics and molecular biology to determining the function of virulence factors that reveal novel facets of the cell biology of host-pathogen interactions.  Our ultimate goal is to understand how these obligate intracellular bacterial pathogens manipulate host cellular functions to replicate, disseminate and cause disease.

A second area of focus in my research group is the development of new methods to perform genetic analysis in many of the microbes that reside in our gut. Understanding how the collection of genetic information of microbes associated with our bodies (microbiomes) impact our health is one of the new frontiers in microbiology.  We are currently studying how bacteria that proliferate in the mucus layers of our gut contribute to nutrient homeostasis and immunological health.

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