1. The document discusses the structure of three types of bacterial viruses (bacteriophages): Lambda phage (λ), T4 phage, and bacteriophage phiX174 (ɸX174). 2. Lambda phage has an icosahedral head containing its DNA and can enter a lysogenic or lytic life cycle in its E. coli host. T4 phage has a contractile tail that helps it infect hosts and contains double stranded DNA. PhiX174 contains a single circle of DNA surrounded by an icosahedral protein capsid. 3. Electron micrographs are provided to show the structure of each type of phage.