Bacteria Genomes - RICKETTSIA CONORII

Rickettsia are obligate intracellular bacteria normally living in arthropod cells. They occasionally cause diseases in humans. R. conorii is the agent of Mediterranean spotted fever, which is transmitted by brown dog ticks.

The bacterium is closely related to R. prowazekii, which causes typhus. Both bacteria are parasites with a relatively small genome, in part because they tend to inactivate their own genes when they can make use of genes from their host. The R. conorii genome has 1.3 million base pairs and 1,374 genes, slightly more than its cousin. The overlap for parts of the genomes is striking: All but thirty genes from a set of 834 in R. prowazekii have counterparts in R. conorii.

R. conorii requires an arthropod (insect) vector for transmission. Transovarian transmission of the pathogen from one generation of insect to the next is important in many rickettsial diseases. From the portal of entry in the skin, rickettsiae spread via the bloodstream to infect the endothelium and sometimes the vascular smooth muscle cells. Common symptons of disease in humans include nausea, vomiting, abdominal pain, encephalitis, hypotension, acute renal failure, and respiratory distress.

References:

http://genomenewsnetwork.org/sequenced_genomes/genome_guide_p3.shtml#psyrin
http://www.ebi.ac.uk/integr8/QuickSearch.do?action=doOrgSearch&organismName=Rickettsia+conorii
Science 290: (5490):347-50 (2000)
Science 293:2093-2098(2001)