Ehrlichia canis str. Jake

Ehrlichia canis is a Gram-negative, obligate intracellular bacterium. It is the causative agent of canine monocytic ehrlichiosis in dogs. It is transmitted by Rhipicephalus sanguineus, the brown dog tick. Rhipicephalus sanguineus is transmitted transstadially: the tick acquires the bacteria by feeding on an infected dog in either the larvae or nymph form and the tick transmits the disease to another dog as either the nymph or adult form. Ehrlichia seem to have a life-cycle composed of three steps. The initial bodies (small spherical structures) are believed to develop into larger multiple membrane-bound units known as morulae. The morulae are inclusions within the cytoplasm of the leukocyte. This morula is thought to then dissociate into small granules called elementary bodies. Symptoms of the acute infection are, among others, lethargy, anorexia, weight loss and even death if the disease is not treated. The genome of Ehrlichia canis (strain Jake) is made up of a single circular chromosome. It contains 17 pseudogenes. A substantial proportion of the genome (27%) is noncoding. It is an aerobic organism that is unable to use glucose or fructose as carbon or energy source, since no transport systems and essential enzymes for the utilization of these substrates were identified. However, amino acids seem to constitute the main energy and carbon source since amino acid transporters and enzymes for the utilization of aspartate, proline, glutamate, glutamine and arginine are present. It possesses biosynthetic pathways for proline, glutamate, glutamine, aspartate, lysine and arginine as well as pathways for purine and pyrimidines, pathways for lipid and phospholipid biosynthesis and for cofactor biosynthesis. Peptidoglycan and lipopolysaccharide seem to be absent from the outer membrane since enzymes for the biosynthesis of lipid A and the murein sacculus as well as for the metabolism of peptidoglycans and amino sugars are not present. Two clusters of Vir homologous proteins were identified. (EBI Integr8)