Annual Review of Microbiology, Vol. 72

My interest in membranes was piqued during a lecture series given by one of the founders of molecular biology, Max Delbrück, at Caltech, where I spent a postdoctoral year to learn more about protein chemistry. That general interest was further refined to my ultimate research focal point—the outer membrane of Escherichia coli—through the influence of the work of Wolfhard Weidel, who discovered the murein (peptidoglycan) layer and biochemically characterized the first phage receptors of this bacterium. The discovery of lipoprotein bound to murein was completely unexpected and demonstrated that the protein composition of the outer membrane and the structure and function of proteins could be unraveled at a time when nothing was known about outer membrane proteins. The research of my laboratory over the years covered energy-dependent import of proteinaceous toxins and iron chelates across the outer membrane, which does not contain an energy source, and gene regulation by iron, including transmembrane transcriptional regulation.