Led by scientists at The Institute for Genomic Research (TIGR) and The Ohio State University (OSU), a team of researchers report the complete genomes of three emerging pathogens that cause ehrlichiosis--Anaplasma phagocytophilum, Ehrlichia chaffeensis, and Neorickettsia sennetsu--and compare the genomes with those of 16 other bacteria with similar lifestyles. The study reports new genes that allow the bacteria to evade a host's immune system, adapt to new niches, and more. Finally, the report reconstructs the metabolic potential of five representative genomes from these bacteria.
"By comparing so many different pathogens, some closely related and others diverse, we're able to identify genes linked to different diseases and organisms," explains molecular biologist Julie Dunning Hotopp of TIGR, first author of the PLoS Genetics paper. Because the pathogens causing ehrlichiosis are obligate intracellular bacteria--able to thrive only inside host cells--they are hard to isolate and study in the lab, Hotopp adds. "How are these diseases different? How are they the same? Can we correlate certain genes with certain characteristics? For the first time, our comparative genomics database offers a resource for tackling these questions."
Recognized since at least the 1930s, ehrlichiosis sickens not only humans, but also dogs, cattle, sheep, and other animals. In Japan, human ehrlichiosis is commonly called sennetsu fever. In the U.S., most human cases have been linked to ticks.