Query: NC_009882:167350 Rickettsia rickettsii str. 'Sheila Smith', complete genome Lineage: Rickettsia rickettsii; Rickettsia; Rickettsiaceae; Rickettsiales; Proteobacteria; Bacteria General Information: This strain was isolated from from a patient with Rocky Mountain spotted fever. Causative agent for Rocky Mountain Spotted Fever. This genus, like other Rickettsial organisms such as Neorickettsia and Anaplasma, are obligate intracellular pathogens and is composed of two groups, the spotted fever group, and the typhus group. 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. Rickettsia rickettsii was first identified by Dr. Howard Rickets as the causative agent of Rocky Mountain Spotted Fever, which was originally named for its geographic distribution at the time, it is now known to be widespread throughout the North American continent. This bacterium is an obligate intracellular pathogen that infects primarily the vascular endothelium, and occasionally smooth muscle tissue. This bacterium is an obligate intracellular pathogen that infects primarily the vascular endothelium, and occasionally smooth muscle tissue. It is passed to the human host from a tick bite, and the tick acts as both a natural reservoir and a vector for disease transmission. Once the organism is endocytosed by the host cell, it quickly escapes the phagozome, and replicates intracellularly, causing cell death and tissue damage. The disease is characterized by a spotted rash and has a high mortality rate if left untreated.
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General Information: This strain has been isolated from the tracheal aspirate of a previously healthy HIV-negative patient with severe respiratory symptoms caused by this infection. Causes urogenital and respiratory disease. This genus currently comprises more than 120 obligate parasitic species found in a wide spectrum of hosts, including humans, animals, insects and plants. The primary habitats of human and animal mycoplasmas are mucous membranes of the respiratory and urogenital tracts, eyes, mammary glands and the joints. Infection that proceeds through attachment of the bacteria to the host cell via specialized surface proteins, adhesins, and subsequent invasion, results in prolonged intracellular persistence that may cause lethality. Once detected in association with their eukaryotic host tissue, most mycoplasmas can be cultivated in the absence of a host if their extremely fastidious growth requirements are met. The latter is one of the major traits that puts them in the separate taxonomic group of microorganisms, class Mollicutes. The cell membrane is rich in protein components (up to two thirds of the membrane mass) that largely consists of highly structurally adaptive lipoproteins employed in invading the host immune system, attachment to the host cells, and pathogenic invasion. Cell division proceeds via normal binary fission or via elongation of a parental cell to form multinucleated filaments and the subsequent breakup to form coccoid bodies.Mycoplasmas carry the smallest genomes of self-replicating cells (less than 500 recognizable coding regions), which is one of the reasons they were among the first microorganisms selected for the genome-sequencing projects. During their evolution, mycoplasmas appear to have lost all of the genes involved in amino acid and cofactor biosynthesis, synthesis of the cell wall and lipid metabolism, resulting in a requirement for the full spectrum of substrates and cofactors taken up from the host or from the complex artificial culture medium. They have lost a number of genes involved in cellular processes, such as cell division, heat shock response, regulatory genes, the two-component signal transduction systems, histidine protein kinases or their target response regulators, and most transcription factors. The majority of mycoplasmas are deficient in genes coding for components of intermediary and energy metabolism and thus are dependent mostly on glycolysis as an ATP-generating pathway. This organism infects humans in the urogenital and respiratory tracts though invasion of tissues. The disease is mainly associated with HIV-1 infection, particularly in the homosexual population, and is very persistent and believed to contribute to the deterioration of the immune system during HIV. Mycoplasma penetrans infection has also been suggested to be a primary cause of some forms of human urethritis and respiratory disease in non-HIV individuals.