A Microbial Biorealm page on the genus Rickettsia typhi
Higher order taxa
Domain:Bacteria, Phylum: Proteobacteria, Class: Rickettsiales, Order: Rickettsiales, Family: Rickettsiaceae
Description and significance
Rickettsia typhi is a small Gram-negative rod bacteria. Therefore, it has an outer membrane and a thin murein layer. Lipopolysaccharides which are unique to bacteria can be found on it’s outer membrane. Rickettsia typhi is the cause of murine typhus, a terrible disease this endemic or murine typhus is much milder than the epidemic typhus caused by R. prowazeki. Infection causes headache, fever, and leads to multisystem disease, including infection of the brain, lung, liver, kidney and heart. Humans become infected when the flea or tick deposits it's feces on the human's skin.
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
The complete genome sequence of R. typhi is 1,111,496 base pairs. There were 877 genes and 838 encode proteins and 24 were unique to R. typhi. The Guanine + Cytosine content in their DNA is 29-30% of it's DNA. R. typhi's genome size is 1080 Mdaltons. It has a circular chromosome
What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
Rickettsiae thrive in environments of high potassium, usually in the cytosol of eukaryotic cells. Membrane transport systems are used to acquire molecules such as ATP and amino acids from the host. However, they have and independent metabolism where they can produce their own ATP and proteins. Rickettsiae enter the cells by phagocytosis but escape and replicate in the cytoplasm. Its inability to maintain intracellular concentrations of several essential nutrients including ATP. Actin polymerization in the cytoplasm can move the microbe through the cytoplasm and into other cells. However this is done poorly and R. typhi remains relatively nonmotile. This allows accumulation of the microbe before the host cell lysis and spreads.
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Humans are affected by this because ticks/fleas can carry this bacteria. Although typhus can be found worldwide, it is mostly present in warm coastal areas. Typhus is uncommon in the United States. It is usually seen in areas where hygiene is poor. Murine typhus is transmitted by exposure to rat fleas or rat feces, or exposure to other infected animals in the environment.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Rickettsia typhi can be transmitted to host by the bite of an infected flea or through the feces of the carrier. In the endothelium is where the microbe divides and transmits itself through feces of the infected. The microbe accumulates after binary fission then the host cell bursts releasing many rickettsia. Destruction of the endothelial cell causes damaged tissue, organs, and loss of blood. Antimicrobial agents are made to enter the host cells and aid in decreasing the effects or R. typhi. Some medications made are doxycycline, tetracycline and chloramphenicol. Developments of insecticides and rat control are being made to decrease the probability of typhus occurring.
In people, typhus causes fever, chills, headache, and general pain. Sometimes a rash is found on the body. The disease is diagnosed through blood testing and is treated with tetracycline, doxycycline, or chloramphenicol. Prevention of the disease is through rodent and flea control.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Murine typhus is caused by R. typhi, however no other useful compunds or enzymes have been found from this microbe that are useful to biotechnology. It's ability to be acquired via aerosol and it's painful sypmtoms make rickettsiae a potential bioweapon and bioterror agent.
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Rickettsiae cannot be cultivated on an artificial medium in the lab. They must be grown in other ways such as in animals or cell cultures.
Enter summaries of the most recent research here--at least three required
(1)Schaechter, Moselio, and Medoff, Gerald, and Eisenstein, Barry. Mechanisms of Microbial Disease, Second Edition. Baltimore, Maryland: Williams & Wilkins, 1993
(2)Schaechter, Moselio, and Engleberg, Cary, and Medoff, Gerald, and Eisenstein, Barry. Mechanisms of Microbial Disease, Third Edition. Baltimore, Maryland: Williams & Wilkins, 1998
(3)Walker, David. Biology of Rickettsial Diseases. Galveston, Texas: CRC Press, 1988
(4)Goodman, Jesse, and Dennis, David, and Sonenshine, Daniel. Tick-Borne Diseases of Humans. Washington, D.C.: ASM Press, 2005
(5)Complete Genome Sequence of Rickettsia typhi and Comparison with Sequences of Other Rickettsiae. 6 April 2007 <http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=516817>
(6)RICKETTSIA, CHLAMYDIA, MYCOPLASMA. 31 April 2007 <http://www.kcom.edu/faculty/chamberlain/Website/Lects/RICKETT.HTM>
Edited by Omar Mendoza student of Rachel Larsen and Kit Pogliano
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