Overview: approaching genetic analysis of diverse bacteria. Bacterial pathogenesis: general concepts in bacterial pathogenesis; paradigms of bacterial pathogenesis - Salmonella typhimurium, Vibrio cholerae. Practical aspects of microbial genetics: genetic nomenclature; microbiological procedures; culture media; antibiotics, antibiotic resistance, and positive resistance, and positive and negative selections; bacterial physiology. Genetic mapping: genetic mapping of chromosomal genes; generalized transduction; genetic mapping by generalized transduction; deletion mapping. Mutants and their analysis: mutagenesis; broad host range allelic exchange systems; suppression; genetic complementation; polarity. Transposons and fusions: uses of transposons in bacterial genetics; bacteriophage mu; operon and gene fusions; operon and gene fusions with lacZ; operon fusions with uidA (gus), gene fusions with phoA, in vivo expression technology. Gene regulation: regulation of virulence genes; challenge phage; genetic analysis of DNA-protein interactions. Recombinant DNA: plasmids and conjugation; transformation and electrotransformation; basic molecular biology techniques; electrophoresis of DNA; polymerase chain reaction. Experiments. Appendices: strains, phage, and plasmids; culture media and supplements; strain colelctions; genetic exchange and mapping; enzyme assays; recombinant DNA methods; plasmid and transposon restriction maps.