Ch 19: Viruses Overview: A Borrowed Life Viruses called bacteriophages can infect and set in motion a genetic takeover of bacteria, such as Escherichia coli Viruses lead ?a kind of borrowed life? between life-forms and chemicals The origins of molecular biology lie in early studies of viruses that infect bacteria Concept 19.1: A virus consists of a nucleic acid surrounded by a protein coat The Discovery of Viruses: Scientific Inquiry Tobacco mosaic disease stunts growth of tobacco plants and gives their leaves a mosaic coloration In the late 1800s, researchers hypothesized that a particle smaller than bacteria caused the disease In 1935, Wendell Stanley confirmed this hypothesis by crystallizing the infectious particle,now known as tobacco mosaic virus (TMV)