Query: NC_017044:130000 Rickettsia parkeri str. Portsmouth chromosome, complete genome
Lineage: Rickettsia parkeri; Rickettsia; Rickettsiaceae; Rickettsiales; Proteobacteria; Bacteria
General Information: Animal pathogen in Mammalia (intracellular obligate). Rickettsiae are obligate intracellular Gram-negative bacteria mostly found in arthropods, some of which cause mild to severe diseases in humans. Rickettsia parkeri, a member of the spotted fever group Rickettsia (SFGR), was first isolated from the Gulf Coast tick, Amblyomma maculatum, in 1937. In 2004, the first confirmed human infection with R. parkeri was reported in a 40-year-old man from the Tidewater area of coastal Virginia. The agent was isolated in cell culture from an eschar biopsy specimen and designated the Portsmouth strain; recently, the first recognized case of tick bite-associated human infection was described.
Subject: NC_011528:535680 Coxiella burnetii CbuK_Q154, complete genome
Lineage: Coxiella burnetii; Coxiella; Coxiellaceae; Legionellales; Proteobacteria; Bacteria
General Information: Coxiella burnetii K Q154 was isolated from a patient with endocarditis and contains the plasmid QpRS. This organism is widely distributed in nature and can cause infections in reptiles, birds, and mammals. It causes Q fever, or 'query' fever, an atypical pneumonia first associated with abattoir workers in Australia. Transmission may be through insect vectors such as ticks that have bitten an infected wild or domesticated animal, or through an aerosol produced by domesticated animals such as sheep or cattle. The presence of a plasmid is believed to be associated with virulence and pathogenicity, however C. burnetii isolates containing plasmid QpDG are avirulent in guinea pigs and plasmidless isolates have been associated with endocarditis in humans. Coxiella burnetii has a developmental life cycle, and can grow vegetatively through binary fission, or asymmetrically and produce a spore-like cell. The spore-like cell may enable the organism to exist extracellularly for small amounts of time. This bacterium is an obligate intracellular pathogen. It is endocytosed by a host cell, a macrophage for example, and lives and replicates inside the phagolysozome, a unique property of this organism. The genome encodes proteins that have a higher than average pI, which may enable adaptation to the acidic environment of the phagolysozome. The chromosome also contains genes for a number of detoxification and stress response proteins such as dismutases that allow growth in the oxidative environment. The type IV system is similar to the one found in Legionella, which may be important for intracellular survival. This organism produces numerous ankyrin-repeat proteins that may be involved in interactions with the host cell. The genome has 83 pseudogenes, which may be a result of the typical genome-wide degradation observed with other intracellular organisms and also has a group I intron in the 23S ribosomal RNA gene.