A Microbial Biorealm page on the genus Ehrlichia chaffeensis
Higher order taxa
Domain: Bacteria; Phylum: Proteobacteria; Class: Alphaproteobacteria; Order: Rickettsiales; family: Anaplasmataceae [Others may be used. Use NCBI link to find]
Description and significance
Ehrlichia chaffeensis causes a tick-borne disease affecting both animals and humans. The first incident of human ehrlichiosis (the infection caused by the Ehrlichia bacterium) was reported in Japan in 1954. An event of human ehrlichiosis was not reported in the United States until 1986. In 1991, E. chaffeensis was isolated from a military recruit stationed at Fort Chaffee, Arkansas, this was the first isolation from a human in the US. (3 Dawson) Public attention peaked after this bacterium was found to be the causative agent of human monocytotropic ehrlichiosis (HME). According to the Center for Disease Control and Prevention (CDC), HME is one of the most frequent life-threatening tick-borne zoonoses (a disease that can be transmitted from an animal to a human) but frequently goes unreported in the United States since symptoms are similar to many other diseases or infections a person may get from insect bites, like Lyme disease from a tick. E. chaffeensis has been isolated in white-tailed deer and even dogs, with the latter being a possible carrier of the tick which can infect humans with HME. E. chaffeensis is also easily contracted in nature where bare skin is exposed and a tick carrying the bacteria can attach and infect. HME is mostly found in the southern states of the US but there are cases reported all over the country as well as in other parts of the world. (2 McQuiston)
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?
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
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?
It is still unknown whether or not E. chaffeensis produces any useful substances. Most major research on this bacterium has occurred in the past ten years, thus its biotechnological impact is still in its infancy.
(1) Dawson, J.E., Anderson, B.E., Fishbein, D.B., Sanchez, J.L., Goldsmith, C. S., Wilson, K. H. and C. W. Duntley. “Isolation and characterization of an Ehrlichia sp. from a patient diagnosed with human ehrlichiosis”. Journal of Clinical Microbiology. 1991. 29(12): p. 2741-2745.
(2) Dumler, J., Choi, Kyoung-Seong, Garcia-Garcia, Jose Carlos and Nicole S. Barat et. al. “Human Granulocytic Anaplasmosis and Anaplasma phagocytophilum” Emerging Infectious Diseases. Volume 11, Number 12, December 2005. p.1828-1834.
(3) Kumagai, Y., Cheng, Z., Lin, M. and Y. Rikihisa. "Biochemical Activities of Three Pairs of Ehrlichia chaffeensis Two-Component Regulatory System Proteins Involved in Inhibition of Lysosomal Fusion." Infect Immun. 2006 September; 74(9): 5014-5022.
(4) Lin, M. and Y. Rikihisa. “Degradation of p22phox and inhibition of superoxide generation by Ehrlichia chaffeensis in human monocytes”. Cell Microbiol. 2007 Apr;9(4):861-74.
(5) Lin, M. and Y. Rikihisa. “Ehrlichia chaffeensis and Anaplasma phagocytophilum lack genes for lipid A biosynthesis and incorporate cholesterol for their survival”. Infect Immun. 2003 Sep;71(9):5324-31.
(6) Lockhart, J. M., Davidson, W. R., Stallknecht, D. E., Dawson, J. E. and E. W. Howerth. “Isolation of Ehrlichia chaffeensis from wild white-tailed deer (Odocoileus virginianus) confirms their role as natural reservoir hosts”. J Clin Microbiol. 1997 July; 35(7): 1681–1686.
(7) McQuiston, J.H., Paddock, C.D., Holman, R.C. and J.E. Childs. “The human ehrlichioses in the United States”. Emerging Infectious Diseases. 1999 Sep-Oct;5(5):635-42.
(8) Miura, K and Y. Rikihisa. "Virulence Potential of Ehrlichia chaffeensis Strains of Distinct Genome Sequences." Infect Immuno. 2007. (in press)
(9) Reeves, W.K., Easterbrook, J.D., Loftis, A.D. and G.E. Glass. “Serologic evidence for Rickettsia typhi and an ehrlichial agent in Norway rats from Baltimore, Maryland, USA”. Vector Borne Zoonotic Dis. 2006 Fall;6(3):244-7.
(10) Schutze, G.E., Buckingham, S.C., Marshall, G.S. and C.R. Woods et al. “Human Monocytic Ehrlichiosis in Children”. Pediatr Infect Dis J. 2007 Jun;26(6):475-479. (in press)
(11) Varela-Stokes, A.S., Stokes, J.V., Davidson, W.R. and S. E. Little. “Co-infection of white-tailed deer with multiple strains of Ehrlichia chaffeensis”. Vector Borne Zoonotic Dis. 2006 Summer;6(2):140-51.
(12) Yu, X.J., McBride, J.W. and D.H. Walker. “Restriction and expansion of Ehrlichia strain diversity”. Vet Parasitol. 2007 Feb 28;143(3-4):337-46.
(13) Zhang, J.Z., Popov, V.L., Gao, S., Walker, D.H. and X.J. Yu. “The developmental cycle of Ehrlichia chaffeensis in vertebrate cells”. Cell Microbiol. 2007 Mar;9(3):610-8. Epub 2006 Sep 20.
Edited by Armen J. Sarkisian, student of Rachel Larsen and Kit Pogliano