Anaplasma phagocytophilum
A Microbial Biorealm page on the genus Anaplasma phagocytophilum
Classification
Higher order taxa
Bacteria; proteabacteria; alphaproteobacteria; rickettsiales; anaplasmataceae; Anaplasma; phagocytophium group (2)
Species
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NCBI: Taxonomy |
Anaplasma phagocytophilum; Anaplasma marginale; Anaplasma platys(2)
Description and significance
Anaplasma phagocytophilum is an intracellular obligate pathogen. It is widely distributed and can be found in North America, Europe, and Asia. Anaplasma phagocytophilum causes the disease Human granulocytic ehrlichiosis(HGE) and is most often spread through tick bites and is thus widely studied. The bacterium infects and colonizes neutrophils in host organisms, often leading to immunodeficiency diseases(1). The Human granulocytic ehrlichiosis pathogen was first described in 1994 in patients in Wisconsin and Minnesota(14). Ticks collected from the area of infection were also discovered to be carriers of the HGE pathogen(14). The infectious agent, first classified as Ehrlichia phagocytophila has recently been reclassified as Anaplasma phagocytophilum(14).
Genome structure
Anaplasma phagocytophilum has one circular genome composed of 1471282 base pairs, composing 1264 protein genes (4). Anaplasma phagocytophilum contains no known plasmids (8).
Cell structure and metabolism
Anaplasma phagocytophilum is a small gram negative bacterium of 0.2-2 micrometer diameter(5). It is a obligate intracellular pathogen and replicates within a host cell vacuole to form a morula microcolony(5). On the membrane surface of Anaplasma phagocytophilum can be found its major antigenic membrane proteins p44 and msp2 both of which are approximately 44-kDa in size(13). These two membrane proteins play a vital role in Anaplasma phagocytophilum virulence. The bacterium has a Type-IV secretion apparatus by which it is able to transfer materials between itself and the host(12). Unlike many gram negative bacterium, Anaplasma phagocytophilum lacks a peptidoglycan layer on their outer membrane(7). In addition, they lack the genes necessary for the biosynthesis of lipid A and peptidoglycan, resulting in very fragile cells that are highly susceptible to stress(7). Anaplasma phagocytophilum is a disease causing intracellular bacterium in dogs, humans, horses and ruminants(3). It lacks lipopolysaccharide biosynthetic machinery(12). The bacterium resides in host endosomes whereby the obtain the nutrients sufficient to carry out binary fission(12). Due to the lack of the ability to synthesize peptidoglycan, Anaplasma phagocytophilum rely on membrane cholesterol to maintain physical integrity(7). Anaplasma phagocytophilum also lack of genes related to the biosynthesis or modification of cholesterol or related sterols(7). All cholesterols are therefore are directly taken from exogenous sources without extensive modification before incorporation into the membrane(7). Anaplasma phagocytophilum is able to carry out major metabolic pathways including glycolysis, citric acid cycle, pentose phosphate pathway(16). It is able to metabolize saccharides such as pentose, fructose, and mannose into metabolic intermediates(16).
Ecology
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Pathology
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Application to Biotechnology
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Current Research
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References
Edited by student of Rachel Larsen and Kit Pogliano
