Synthesis of DNA and protein by Anaplasma marginale in bovine erythrocytes during short term culture

Bovine erythrocytes infected with A. marginale were cultured for 1 to 5 days in a CO₂ incubation chamber, pulse-labeled with [³H]thymidine and [¹⁴C]methionine, lysed, and fractionated by differential centrifugation and continuous density gradient centrifugation in Renografin. Anaplasma and associated fragments of stroma formed two distinct bands in the dense region of the gradient. Electron microscopic examination of pelleted material from the bands from cells cultured for 1 day revealed the presence of organisms that were morphologically intact or in various states of degeneration. Examination of fractions from the gradient for incorporation of label revealed that anaplasma present in erythrocytes can incorporate both [³H]thymidine and [¹⁴C]methionine. Subsequent experiments demonstrated that organisms cultured for 3 and 5 days incorporated the radiolabeled compounds also, but to a lesser extent. The experiments demonstrate that it is possible to culture anaplasma in vitro for short periods of time and monitor their growth characteristics.