The van Opijnen lab studies the genes that allow a bacterial species to become infectious. Within a given species of bacteria, one strain may be harmless, and another potentially lethal. Such drastic differences are perhaps not surprising: Recent studies indicate that one strain of a specific bacterial species may differ from another strain of the same species by 200 genes. Furthermore, many of these microbes can swap their DNA. Thus, any search for the genes that fuel infectiousness should include all of the genes available within the entire species. I will take advantage of an innovative sequencing technique developed in Dr. van Opijnen's lab in order to analyze the genetic material of 50 strains of Streptococcus pneumoniae and identify the genes that are most important for infecting a host and causing disease. This work has clear implications for the understanding and treatment of infectious diseases.