Tuesdays, 4:00 - 5:00pm T-639 UW Health Sciences Building
**Unless otherwise noted
Tuesday, October 5, 2010, 1PM- T733 HSB
Lucas R. Hoffman, M.D., Ph.D.
Assistant Professor of Pediatrics, Pulmonary Division, Department of Pediatrics, University of Washington
"Bacterial adaptation during chronic, polymicrobial infections: Lessons from cystic fibrosis.”
The advent of antibiotics in the 20th century revolutionized the treatment of many types of infections. However, chronic infections, which frequently involve multiple microbial species infecting together, are often poorly responsive to antibiotic therapy. Chronic, polymicrobial infections therefore represent a key frontier in infectious disease research, presenting a substantial global burden of disease. The polymicrobial chronic lung infection in the airways of people with cystic fibrosis (CF) serves as a paradigm for studying the behavior of multispecies microbial communities infecting human tissues. In this seminar, I will describe recent findings by us and others indicating that bacteria infecting CF airways interact on a molecular level, and that these interactions impact response to antibiotics. Often, these effects could not have been identified by the single-species cultures routinely used to characterize these infections. I will describe how these findings, obtained from relatively simple models and clinical observations, motivated our laboratory’s current translational approach to studying complex, polymicrobial interactions.
Tuesday, October 5, 2010, 4PM- T639 HSB
Gerard P. Andrews, Ph.D.
Assistant Professor, Veterinary Sciences, Medical Microbiologist, University of Wyoming
"Application of In Vivo–induced Antigen Technology (IVIAT) Reveals Genes Associated with Persistence of Brucella abortus in the Mammalian Host."
The exact mechanisms of Brucella abortus pathogenesis in humans and animals remain obscure; however through the use of in vivo-induced antigen technology (IVIAT), it has become easier to identify genes important for this pathogen’s survival in a susceptible host. In this regard, serum collected from sero-positive elk at the National Elk Refuge in Jackson, Wyoming, was pooled and absorbed against in vitro grown cultures of Brucella abortus to remove antibody reactive against constitutively expressed antigens. E. coli expression libraries of B. abortus genomicDNA were next prepared and screened by colony immunoblot using the pooled, absorbed elk sera. Reactive clones were isolated, rescreened by immunoblot, and recombinant plasmid inserts sequenced. To date, screening of approximately 35,000 clones has yielded ten genes whose products were confirmed reactive with the absorbed serum. These loci included: malate dehydrogenase (Mdh), an outer membrane protein, Omp25d, an iron ABC transporter component, AfuA, a putative membrane lipoprotein, D15, and a component of a Type-IV secretion system, VirJ. Immunoblotting results of recombinant products from these five IVI genes revealed unique serologic patterns which delineated between naive animals and those infected with two different strains of B. abortus (in both elk and cattle). Furthermore, immunization with at least two of these proteins reduced bacterial load in challenged, vaccinated mice relative to naïve animals. Examination of spleens from infected immune mice suggested increased inflammatory responses which correlated with increased INF-g levels compared to the unimmunized controls. In vitro analysis of Mdh was shown to stimulate high levels of the anti-inflammatory cytokine, IL-10, compared to other recombinant proteins and medium alone, as well as stimulate proliferation of splenocytes. Taken together, our data suggest that anti-inflammatory processes induced by the pathogen may be neutralized with the appropriate stimulation of humoral immunity, which counters the traditional paradigm that a robust cellular response is sufficient for clearance of brucellosis. Continued library screening, as well as further characterization of the remaining ten IVI gene products, may not only clarify the genetic pattern of the pathogen’s infection/survival in susceptible hosts, but potentially identify virulence factors critical in eliciting a protective immune response to brucellosis.
Monday, October 11 2010, 12:30PM- T739 HSB
Christopher Neumann, Ph.D.
Research Fellow in Biological Chemistry and Molecular Pharmacology, Harvard Medical School
"The Chemistry and Biology of Enzymatic Halogenation.”
In biological systems, the modulation of signaling pathways and mediation of ecological interactions can be performed by small organic molecules. Enzymatic halogenation is a unique and versatile chemical process that allows producing organisms to build and tailor these natural products for maximum biological effect, and many halogenated compounds (e.g., vancomycin) have proven applications in treating human disease. In this talk, I will present two contrasting examples of enzymatic chlorination from prokaryotic and eukaryotic microbial systems. In the first case, our studies on the kutzneride family of antifungal compounds led to the elucidation of a pathway where chlorination serves not as an endpoint, but rather as an intermediate step in the biosynthesis of an unusual non-proteinogenic amino acid. This result provides a valuable new cassette of genes that can be used in future efforts to engineer antibiotic biosynthesis in microbes. In the second example, we have been exploring the biosynthesis of chlorinated polyketides in the social amoeba Dictyostelium discoideum. Using a combined biochemical and genetic approach, we have elucidated the enzyme responsible for chlorination in the biosynthesis of the morphogen Differentiation-Inducing Factor (DIF)-1, and confirmed that this gene is essential for proper development of starved cells into a multicellular fruiting body. Ongoing studies are aimed at understanding the function of this same gene in the production of chlorinated antibacterial compounds after development, thus suggesting multiple biological roles for a single halogenase in this species.
Tuesday, October 19, 2010, 4PM- T639 HSB
John Collier, Ph.D.
Presley Professor of Microbiology and Molecular Genetics
Harvard Medical School
"An Ode to Diphtheria Toxin”
The study of diphtheria toxin in the late 1800‘s and early 1900‘s revealed a simple and effective way to vaccinate against diphtheria, which in turn led to the virtual eradication of the disease in industrialized nations. After diphtheria ceased to be a major threat, diphtheria toxin became a model system for understanding how a microbial toxin can damage a mammalian host. Studies on the protein's production, structure and mode of action have yielded insights of major importance in understanding bacterial pathogenesis. In this lecture I outline the history of studies on diphtheria toxin, describing some key experiments and the scientists who performed them.
Tuesday, October 26, 2010, 4PM- T639 HSB
Sandra Weller, Ph.D.
Visiting Professor (Sabbatical), Chemical and Systems Biology, Stanford University Medical Center
“How HSV-1 commandeers cellular DNA damage and protein quality control machinery.”
When a virus infects a cell it must contend with a hostile environment and host machinery that is intrinsically antiviral. One
of the hallmarks of Herpes Simplex Virus (HSV) infection is the
dramatic reorganization of the infected cell nucleus leading to the
formation of large globular replication compartments in which gene expression, DNA replication and encapsidation occur. During
infection, cellular factors that are beneficial to the virus are hijacked while other factors and pathways are degraded or
inactivated. Two of the cellular homeostatic pathways affected by
HSV-1 infection are the protein quality control (PQC) and DNA damage
response pathways. These events are orchestrated by immediate-early
and early viral proteins that play roles in remodeling the infected
cell nucleus, hijacking host PQC machinery and manipulating cellular
DNA damage responses. This seminar will also describe the role of
viral and host proteins during HSV DNA replication. We are
particularly interested in how the two subunit viral recombinase
(UL12 and ICP8) interacts with cellular repair proteins during this