Mexican scientists Emma Galindo and Jorge Olarte to investigate new forms of penicillin resistance in Shigella isolates from pediatric patients in Mexico City, which lead to the discovery of new forms of "R factors" - genes responsible for antimicrobial resistance. Falkow and trainee Joan Skerman Knapp identified a virulence factor on plasmids of E. coli found in human feces, demonstrating for the first time that the ability to cause disease may be transferable between bacteria. Falkow was present at the famous Waikiki beach meeting in 1972 between Herb Boyer (who provided the restriction enzyme EcoRI) and Stanley Cohen (who provided the plasmid) that led to a plan to develop recombinant DNA technology. This led to the first cloning of a bacterial virulence factor, the heat stable toxin of E. coli, in a seminal 1976 paper with Magdalene Yh So, which heralded the application of molecular genetics to understanding gene transfer, and ultimately led to the creation of the field of synthetic biology. Falkow and his trainees developed many methods that moved biological research forward such as: a method for screening patient samples for enteric pathogens, the identification of Salmonella and Shigella in patient samples based on lysine metabolism, the application of nucleic acid hybridization to distinguish different bacterial species, the application of agarose gels to isolate plasmids of various sizes, isolation and creation of different plasmid backbones now used as cloning vectors, a method for identifying unculturable pathogens based on isolated 16S ribosomal RNA sequence, an optimized version of GFP for flow cytometry applications, and a fluorescence-based method for the detection of genes expressed by pathogens inside of host cells, among many other techniques. After studying the DNA content of many different pathogenic microbes, Falkow became one of the first scientists to suggest bacterial taxonomy should be based on DNA composition rather than phenotypic observations. Falkow and others created the universal nomenclature scheme for plasmids still in use today. Falkow established ‘Molecular Koch’s postulates’ for defining virulence determinants, which continues to influence thinking and experimental design in infectious disease research. Teaching and Service Falkow valued and enjoyed teaching as a fundamental part of scientific training and believed that all scientists have a duty to teach and train the next generation. In all of his years of employment at academic institutions, he taught students in some capacity between medical, graduate, undergraduate courses and invited lectures for courses whenever he was able