Rickettsia typhi

From MicrobeWiki, the student-edited microbiology resource
Revision as of 18:49, 5 June 2007 by Ojmendoz (talk | contribs)

A Microbial Biorealm page on the genus Rickettsia typhi

Classification

Higher order taxa

Domain:Bacteria, Phylum: Proteobacteria, Class: Rickettsiales, Order: Rickettsiales, Family: Rickettsiaceae

Species

NCBI: Taxonomy


Rickettsia typhi

Description and significance

Rickettsia typhi is a small Gram-negative rod bacteria. Therefore, it has an outer membrane and a thin murein layer. Murein is a strong polymer found in the cell walls of prokaryotes. 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 can lead 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.

American Society for Microbiology-MicrobeLibrary.org: Rickettsia, Obligately Intracellular Bacteria, Pathogenic for Humans I [ http://www.microbelibrary.org/images/Walker/images/rick2-an.jpg ].

Genome structure

The complete genome sequence of R. typhi is 1,111,496 base pairs. There were 877 genes, 838 encode proteins and 24 were unique to R. typhi. The Guanine + Cytosine(G+C) content in it's DNA is roughly 29-30% of it's DNA. R. typhi's genome size is 1080 Mdaltons and it has the typical prokaryote circular chromosome. Currently, no plasmids have been found in this microbe.

Cell structure and metabolism

Rickettsiae thrive in environments with a high concentraion of potassium an a low concentration of glucose(sugar), usually this is the cytosol of eukaryotic cells. Cell membrane transport systems are used to acquire molecules such as ATP(energy) and amino acids from the host. This is one of many ways this microbe exploits it's host. Its inability to maintain concentrations of essential nutrients like ATP. Make R. typhi relatively non-motile. This non-motility allows for accumulation of the microbe in the host cell, which causes the cell to lyse/burst. However, they have and independent metabolism where they can produce their own ATP and proteins. Rickettsiae enter the cells by phagocytosis, a process where a microorganism enters a cell through it's membrane. Later they escape and replicate in the cytoplasm.

Ecology

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.

Pathology

Rickettsia typhi can be transmitted to host by the bite of an infected flea or through the feces of the carrier. Typically, in the endothelium tissue is where the microbe divides and transmits its infection. The microbe accumulates 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.

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?

Current Research

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. Developments of insecticides and rat control are being made to decrease the probability of typhus occurring.

Enter summaries of the most recent research here--at least three required

References

(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

Retrieved from "http://microbewiki.kenyon.edu/index.php/Genus_larsen"