A Microbial Biorealm page on the genus Rickettsia prowazekii
Higher order taxa
Bacteria; Proteobacteria; Alphaproteobacteria; Rickettsiales; Rickettsiaceae
Description and significance
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.
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
The R. prowazekii genome is circular, containing 1,111,523 base pairs and 834 protein coding genes. Also, 24% of R. prowazekii DNA is non-coding- the largest amount in any microbial genome. No genes code for anaerobic glycolosis, however, complete coding sequences for the tricarboxylicacid (TCA) cycle and respiratory-chain complex are found indicating R. prowazekii is the closest microbial ancestor to mitochrondia.
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
R. prowazekii is a Gram-, intracellular bacteria with a bacilli structure. LPS and Peptidoglycan biosynthesis are both completely coded for in R. prowazekii'.
As mentioned above, R. prowazekii cannot undergo any glycolytic pathway that will produce pyruvate. However, enzymes required for pyruvate metabolism are coded for by Rickettsia indicating that the microbe must acquire it somehow. One such mechanism for this acquisition is acquiring PEP directly from it's host. Rickettsia also lack coding sequences for Nitrogen metabolism which allows the synthesis of glutamine, indicating that, like PEP, glutamine must be acquired directly from the host cells.
Other methods for Rickettsia to gain energy include oxidative phosphorylation and ATP translocases. First, Rickettsia code for ATP translocases- there are 5 copies for these genes in their genome indicating the importance they have in energy acquisition for the microbe. The translocases allow the cell to take up ATP produced by the host. This is the major ATP acquiring method for Rickettsia since the cell will use translocases upon first entering a host cell to capture the host ATP before initiating its own pathways. Once the rickettsiae has used up all the host ATP, it will initiate the electron transport chain, which culminates with ATP Synthase and the production of ATP.
Another key molecule produced is polyhydroxyalkanoate (PHA), the concentration of which increases in low nutrient environments. PHA's are great carbon storing molecules and in the case of cellular starvation, PHA will serve as a carbon and energy source to maintain survival.
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Enter summaries of the most recent research here--at least three required
S.G. Andersson, A. Zomorodipour, J.O. Andersson, T. Sicheritz-Ponten, U.C. Alsmark, R.M. Podowski, A.K. Naslund, A.S. Eriksson, H.H. Winkler and C.G. Kurland, The genome sequence of Rickettsia prowazekii and the origin of mitochondria, Nature396 (1998), pp. 133–140.
Edited by Matthew Noble, student of Rachel Larsen