Valdivia Receives Merck Irving S. Sigal Memorial Award

DURHAM, N.C. (February 2007) — Raphael Valdivia, PhD, an assistant professor in the Department of Molecular Genetics and Microbiology at the Duke University Medical Center, was selected to receive the Merck Irving S. Sigal Memorial Award from the ASM for 2007. Dr. Valdivia is honored for his established record of creative and independent research in the area of molecular and cellular microbiology.

Dr. Valdivia received his B.S. in Microbiology, Cornell University, Ithaca, New York, and his Ph.D. in Microbiology and Immunology at Stanford University School of Medicine, Stanford, California. As a graduate student, Dr. Valdivia pioneered the use of fluorescent reporter proteins as probes for pathogen gene expression during host infection. He and Dr. Brendan Cormack, developed green fluorescent protein mutants with enhanced fluorescent properties and applied flow cytometric techniques to identify bacterial genes that are specifically activated in infected cells. This work led to the discovery of novel virulence factors in the enteric pathogen Salmonella typhimurium.

As a postdoctoral fellow at the Howard Hughes Medical Institute, University of California, Berkeley, Dr. Valdivia turned his focus to the genetic and biochemical analysis of protein sorting in the endosomal system of the model yeast Saccharomyces cerevisiae. His postdoctoral work led to the discovery of a previously unrecognized function of a yeast clathrin adaptor protein complex in sorting membrane proteins in the Golgi, and later in uncovering a role for cell stress signaling pathways in regulating the transport of cell wall biosynthetic enzymes to the plasma membrane.

As an independent investigator, Dr. Valdivia merged his expertise in microbial pathogenesis and cell biology to study the cellular microbiology of obligate bacterial pathogens. His laboratory has established an S. cerevisiae-based expression system to identify and characterize virulence factors from the sexually transmitted pathogen Chlamydia trachomatis that target host membrane and lipid transport pathways.

Dr. Valdivia has been the recipient of several awards, including a Damon Runyon Postdoctoral Fellowship and a career development award from the Pew Scholar’s Program in the Biomedical Sciences. Dr. Valdivia was nominated by Dr. Thomas D. Petes, Chair, Department of Molecular Genetics and Microbiology and Joseph Heitman, Director of the Center for Microbial Pathogenesis, Duke University Medical Center.