Changes in buoyant density relationships of two cell types of Coxiella burneti phase I

Abstract

Coxiella burneti phase I, purified from a formalin-inactivated yolk-sac vaccine, was separated into two bands of morphologically distinct cell types when subjected to sucrose gradient centrifugation. Recycling of the less dense, rod-shaped cells in unbuffered sucrose gradients (pH 5.5 to 6.0) resulted in the formation of bands having the location and appearance of the original two bands. Recycling of the denser band of larger ovoid-shaped cells yielded a single band, suggesting that the larger cell type arose from the smaller cell. In contrast to vaccine-derived rickettsiae, live, cell culture-propagated phase I organisms formed a single band in unbuffered sucrose gradients, at the same density as the upper band of the vaccine preparation. Centrifugation of cell culture-derived rickettsiae for 26 to 48 h in sucrose gradients of pH 5.5 resulted in the formation of a second band, at the same density as the lower band of the vaccine preparation. This did not occur in gradients of pH 7.0. Treatment of cell culture-propagated rickettsiae with formalin or germicidal ultraviolet radiation induced a total shift of the less dense cell population to a zone of higher density when centrifuged isopycnically in CsCl gradients. This density change did not occur in sucrose gradients, suggesting a difference in the effect of these treatments on the permeability of the cell membrane to sucrose and CsCl.

Electron microscopic study on the interaction between normal guinea pig peritoneal macrophages and Coxiella burnetii

“…Although we cannot directly rule out the possibility that there is a complex cycle in the multiplication of C. burnetii, our data do not support it. Other investigators have observed two morphological types of phase I or II C. burnetii after purification by density gradient centrifugation (9,28,29). Wiebe et al (29) speculated that the oval to round forms may be degenerate forms produced by host-mediated digestion or alteration by chemical treatment :o .…”

“…5 ,tm. or that they may represent two stages in a complex developmental cycle. Wachter et al (28) indicated that the larger forms could be derived from the rod-shaped rickettsiae by various stresses.…”

Q Fever

“…burnetii displays a complex intracellular cycle, leading to the formation of spore-like forms (227). McCaul and Williams (228) have proposed the terms "small-cell variant" (SCV) and "large-cell variant" (LCV) to differentiate the two C. burnetii cell forms observed in persistently infected cells (48,251,388,398). SCVs and LCVs correspond to different intracellular development stages of C. burnetii (227).…”

Some characteristics of heavy and light bands of Rickettsia prowazekii on Renografin gradients

“…The experiments reported here do pertain to reports of heterogeneous rickettsial banding in CsCl gradients, however. C. burnetii in phase I gave rise in two bands in CsCl (22), and inactivation with Formalin (18,19,22) or ultraviolet light (18, 19) caused a shift of organisms from the light to the heavy band. (It also has been reported that lengthy centrifugation of C. burnetii at lowered pH in sucrose caused the appearance of a heavy band, but that ultraviolet light or Formalin treatment, which caused heavy band formation in CsCl, did not have that effect in sucrose [18]).…”

“…C. burnetii in phase I gave rise in two bands in CsCl (22), and inactivation with Formalin (18,19,22) or ultraviolet light (18, 19) caused a shift of organisms from the light to the heavy band. (It also has been reported that lengthy centrifugation of C. burnetii at lowered pH in sucrose caused the appearance of a heavy band, but that ultraviolet light or Formalin treatment, which caused heavy band formation in CsCl, did not have that effect in sucrose [18]). Noninactivated phase I C. burnetii which naturally formed two bands in CsCl also were easily distinguished morphologically, the rickettsiae in the upper band being smaller with more condensed nucleoids than those in the lower band (22).…”