Purification of Rickettsia rickettsi by density-gradient zonal centrifugation

Authors:
  • RAR. L. Anacker
    R. L. Anacker
  • RGR. K. Gerloff
    R. K. Gerloff
  • LTL. A. Thomas
    L. A. Thomas
  • RMR. E. Mann
    R. E. Mann
  • WBW. R. Brown
    W. R. Brown
  • WBW. D. Bickel
    W. D. Bickel
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Abstract
Rocky Mountain spotted fever rickettsiae, cultivated either in yolk sacs of embryonated chicken eggs or in mouse L cells, were purified by centrifugation through a linear sucrose density gradient in a zonal rotor. Under the conditions of the experiments the rickettsiae banded at a density of about 1.21. Intact organisms with what appeared to be large translucent capsules were found in this band. The degree of purity was high because yolk sac contamination was not detected in rickettsial suspensions derived from embryonated eggs, and little extraneous material was observed by electron microscopy in suspensions obtained from either host. About 4 × 108 rickettsial particles were recovered from each gram of yolk sac and 2 × 1010 particles from each gram of L cells, a 50-fold difference. Each milligram dry weight of purified rickettsiae contained about 1 × 1010 particles.