Francisella tularensis

Image of tularemia lesion
A Tularemia lesion on the dorsal skin of right hand. Tularemia is caused by the bacterium, Francisella tularensis. Symptoms vary depending on how the person was exposed to the disease, and as is shown here, can include skin ulcers. Source: CDC Public Health

About the Project

P.I.: George Weinstock (BCM-HGSC), Joseph Petrosino (BCM-HGSC)
Collaborators: Rebecca Morton (Oklahoma State University), Kenneth Clinkenbeard (OSU)
Genome size:  
Strain: ATCC6223
Current Status of the Project
Latest assembly date: 6-27-2006
Total number of reads: 434,995
Coverage: 24x (for 1.9 Mb gneome)
Number of contigs: 88
N50 contig size: 32049 bp
Number of scaffolds: NA
N50 scaffold size: NA
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About Francisella tularensis ATCC6223

F. tularensis, a small, nonmotile, nonsporulating, gram-negative, coccobacillus is currently one of the most infectious bacteria known and is the causative agent of the systemic disease tularemia, a potentially severe and fatal disease in humans. F. tularensis is also characterized by its resilience to environmental conditions and its ease of dissemination. For these reasons, F. tularensis poses a serious threat to laboratory workers who handle the organism and is a bioterrorism concern.

The gamma-protobacterial family Francisellaceae consists of two genera: Francisella tularensis and Francisella philomiragia. F. tularensis has four subspecies: tularensis (Type A), holarctica (Type B), mediaasiatica (geographically restricted to the central Asia) and novicida (a rare isolate initially isolated from a water source in Utah in 1951). F. tularensis subsp. tularensis, is the most virulent subspecies and is geographically restricted to the North American continent, with only one report of isolation of Type A in Europe. Subspecies holarctica is moderately virulent and is found throughout the Northern hemisphere including the Scandinavian countries, Russia, Spain, Japan and the U. S. Because the subspecies are very similar, diagnostic microbiological identification has relied on differences in virulence and in a small number of non-routine biochemical/DNA assays (e.g. PCR-based DNA fingerprinting analyses).

The subsp. holarctica live attenuated vaccine strain (LVS) is currently the only effective vaccine against tularemia. The vaccine is approved in the U.S. only for use in clinical trials, and its future availability is undetermined because the protective response offered by the vaccine has not been well characterized, the basis of its attenuation is unknown, and the LVS strain is fully virulent when delivered intraperitoneally in mice. The fact that the LVS provides protective immunity suggests that efforts to create a defined attenuated mutant may be fruitful, however such strains may not be available for some time.

ATCC6223, also known as B38, is an attenuated Type A strain. The sequence data from this genome will serve as a comparative reference to aid in the identification of Type A virulence factors and will provide further data toward identifying the genetic determinants that distinguish Type A pathogenicity and geographic distribution.

Christopher, G.W., Cieslak, T.J., Pavlin, J.A., and E.M. Eitzen. 1997. Biological warfare: a historical perspective. JAMA 278:412-417

Tarnvik, A. 1989. Nature of protective immunity to Francisella tularensis. Rev. Infect. Dis. 11:440-451.

Gurycova, D. 1998. First isolation of Francisella tularensis subsp. tularensis in Europe. Eur. J. Epidemiol. 14:797-802.