summaries of swami and friends

Topics: Typhus, Rickettsia, Bacteria Pages: 3 (1100 words) Published: June 23, 2014
The Rickettsiae are small (0.3-0.5 x 0.8-2.0 um), Gram-negative, aerobic, coccobacilli that are obligate intracellular parasites of eucaryotic cells. They may reside in the cytoplasm or within the nucleus of the cell that they invade. They divide by binary fission and they metabolize host-derived glutamate via aerobic respiration and the citric acid (TCA) cycle. They have typical Gram-negative cell walls, and they lack flagella. The rickettsiae frequently have a close relationship with arthropod vectors that may transmit the organism to mammalian hosts. The rickettsiae have very small genomes of about 1.0-1.5 million bases. Rickettsia prowazekii, the cause of epidemic typhus, is the prototypical rickettsia. Typhus has plagued humanity throughout history. The American bacteriologist, Hans Zinsser, to whom this textbook is dedicated, was able to grow the elusive intracellular pathogen and develop a protective vaccine for typhus fever. He wrote a book about the bacterium, published in 1935, Rats, Lice, and History: "being a study in biography, which, after 12 preliminary chapters indispensable for the preparation of the lay reader, deals with the life history of typhus fever". Rickettsia prowazekii has made science news recently since it has been shown to be the probable origin of eucaryotic mitochondria. Its complete genome sequence of 1,111,523 base pairs has been shown to contain 834 protein-coding genes. The functional profiles of these genes show similarities to those of mitochondrial genes. No genes required for glycolysis are found in either R. prowazekii or mitochondrial genomes, but a complete set of genes encoding components of the tricarboxylic acid cycle and the respiratory-chain complex is found in both. In effect, ATP production in the rickettsia is the same as that in mitochondria. Many genes involved in the biosynthesis and regulation of biosynthesis of amino acids and nucleosides in free-living bacteria are absent from R. prowazekii and...
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