Ar. Alleman et al., ANALYSIS OF THE ANAPLASMA-MARGINALE GENOME BY PULSED-FIELD ELECTROPHORESIS, Journal of General Microbiology, 139, 1993, pp. 2439-2444
Anaplasma marginale is a rickettsial parasite of bovine erythrocytes c
ausing world-wide economic losses in livestock production. Despite its
importance, little is known about this rickettsia at a molecular leve
l because it has not been cultured in vitro, and there is no small-ani
mal model. Although several genes have been cloned and sequenced, the
gross genome structure of the organism has not yet been well character
ized. We separated intact bovine erythrocytes from leucocytes, and det
ermined the genome size of A. marginale by use of restriction endonucl
ease cleavage and pulsed-field gel electrophoresis (PFGE). A value of
56 mol % G + C was obtained for this genome by spectral analysis. Undi
gested A. marginale DNA failed to migrate under several different elec
trophoretic conditions, indicating a circular genome. Digestions of in
tact A. marginale DNA were performed using restriction endonucleases N
otI, SfiI and PacI. Complete digestion with SfiI resulted in 12 distin
ct bands ranging in size from 14 to 170 kbp. Total size determined by
addition of SfiI-digested fragments was approximately 1200 kbp. PacI c
leaved the A. marginale genome from three different isolates into just
three fragments, of 598, 557 and 97 kbp. Incomplete digestion produce
d a band measuring 1250 kbp. These results indicate that A. marginale
has a circular genome between 1200 and 1260 kbp, with a G + C content
of 56 mol %.