Query: NC_006142:811469 Rickettsia typhi str. Wilmington, complete genome
Lineage: Rickettsia typhi; Rickettsia; Rickettsiaceae; Rickettsiales; Proteobacteria; Bacteria
General Information: This genus, like other Rickettsial organisms such as Neorickettsia and Anaplasma, is composed of obligate intracellular pathogens. The latter is composed of two organisms, Rickettsia prowazekii and Rickettsia typhi. The bacteria are transmitted via an insect, usually a tick, to a host organism, in this case humans, where they target endothelial cells and sometimes macrophages. They attach via an adhesin, rickettsial outer membrane protein A, and are internalized where they persist as cytoplasmically free organisms. Transovarial transmission (from mother to offspring) occurs in the invertebrate host. Rickettsia typhi causes murine typhus and is an obligate intracellular pathogen that infects both the flea vector and hosts such as human, rat, and mouse. In the flea vector, the bacterium penetrates the gut epithelial barrier and is found in the feces which become infective.
Subject: NC_003210:2721559 Listeria monocytogenes EGD-e, complete genome
Lineage: Listeria monocytogenes; Listeria; Listeriaceae; Bacillales; Firmicutes; Bacteria
General Information: This strain has numerous pathogenicity islands and genes as compared to the related non-pathogenic organism Listeria innocua. This organism, which causes listeriosis, is one of the leading causes of death from food-borne pathogens especially in pregnant women, newborns, the elderly, and immunocompromised individuals. It is found in environments such as decaying vegetable matter, sewage, water, and soil, and it can survive extremes of both temperatures (1-45 degrees C) and salt concentration marking it as an extremely dangerous food-born pathogen, especially on food that is not reheated. This organism is enteroinvasive, and utilizes an actin-based motility system by using a surface protein, ActA, that promotes actin polymerization, to spread intercellularly using the polymerized cytoskeletal protein as a "motor". There are 13 serovars associated with Listeria monocytogenes, and the serovar 4b strains are more commonly associated with invasive disease.