Research in VMP at the College of Veterinary Medicine

The Anaplasma marginale Genome Sequencing Project

Anaplasma marginale is the most prevalent tick-borne pathogen of cattle worldwide. The disease results in significant morbidity and mortality in U.S. cattle and is a constraint to export. Critically, there is no federally licensed vaccine available and the live, blood-based vaccines widely used in tropical countries cannot be licensed in the U.S. due to the risk of transmitting both known and unknown pathogens. A vaccine for anaplasmosis is a priority for the USDA National Cattlemen’s Beef Association and many other research groups worldwide.

A. marginale is the type species for the genus Anaplasma which contains both animal and human pathogens.

The first strain selected for sequencing was the St. Maries strain as it represents a virulent tick transmissible strain. The second strain selected for sequencing was the virulent non-tick-transmissible Florida strain. These projects were completed using a targeted BAC-based clone-by clone approach. More recent genome projects have employed pyrosequencing to provide >96% genome coverage of the Virginia, Puerto Rico and Mississippi strains.

The A. marginale centrale subspecies genome was sequenced using a traditional shotgun based approach.

The A. marginale genome sequences were generated with funding from USDA/ARS CRIS, USDA CSREES and the Wellcome Trust.

The figure shows genome maps of the St. Maries and Florida strains. The inner most circle shows GC skew, the next circle show positions of tRNA (purple) and rRNA (orange) genes. The positions of CDSs are indicated as bars with genes on the reverse strand shown within the circle depicting genes on the forward strand. The St. Maries strain then shows the positions of the BAC clones (blue and pink arcs) or gap spanning PCR fragments (green and yellow arcs) that were used to obtain the complete sequence. The next ring shows the locations of the msp1, 2, 3 genes, while the outermost ring indicates the genome size coordinates (in 100 kb increments). The Florida strain map shows genome size (in bp) below the black circle. The outer four series of bars indicate repetitive genes (black), and regions missing from pyrosequenced genomes relative to the FL sequence: Virginia (blue), Puerto Rico (red) and Mississippi (green).

Publications

Brayton, K. A., D. P. Knowles, T. C. McGuire, and G. H. Palmer. Efficient use of a small genome to generate antigenic diversity in tick-borne ehrlichial pathogens. Proceedings of the National Academy of Sciences. 98: 4130-4135, 2001.

Brayton, K. A., L. S. Kappmeyer, D. R. Herndon, M. J. Dark, D. L. Tibbals, G. H. Palmer, T. C. McGuire and D. P. Knowles Jr. Complete genome sequencing of Anaplasma marginale reveals that the surface is skewed to two superfamilies of outer membrane proteins. Proceedings of the National Academy of Sciences. 102: 844-849, 2005.

Dark, M. J., D. R. Herndon, L. S. Kappmeyer, M. P. Gonzales, E. Nordeen, G. H. Palmer, D. P. Knowles, Jr., and K. A. Brayton. Conservation in the face of diversity: Multistrain analysis of an intracellular bacterium. BMC Genomics. 10: 16. 2009.