Permeability Properties of Rickettsia mooseri

Abstract

The passive permeability properties of Rickettsia mooseri to both inorganic and organic solutes have been examined. Visual observations by phase-contrast microscopy of rickettsiae in macerated yolk sacs taken directly from heavily infected eggs revealed plasmolysis with hypertonic NaCl and KCl as well as with sucrose solutions. In contrast, similar visual studies of rickettsiae which had been subjected to freezing or to a purification process, or both, were plasmolyzed by hypertonic sucrose but not by hypertonic NaCl and KC1. These primary observations were extended to a variety of solutes and were placed on a quantitative basis by use of optical density and radioisotope dilution methods. Intracellular Na+ and K+ concentrations in processed rickettsiae, measured by flame photometry, closely paralleled the concentration of these ions in the suspending medium. It was concluded that R. mooseri appears to possess an osmotically active, functional, and structural membrane distinct from the cell wall, located at the surface of a structure analogous to the bacterial protoplast. In the intact organism, this membrane is passively impermeable to sucrose, NaCl, and KCl. However, altered permeability properties, especially to inorganic electrolytes, may be expected in rickettsiae which have been stored in the frozen state and subjected to a lengthy purification process. The basis for the apparent obligate nature of intracellular parasitism among pathogenic rickettsiae remains unknown. With their relatively

INFLUENCE OF OSMOTIC PRESSURE ON TRANSFORMABLE AND NON TRANSFORMABLE VARIANTS OF NEISSERIA MENINGITIDIS.

“…meningitidis cells behave as osmometers upon changes in osmotic pressure at least from 1.5 atmospheres to above 24. Similar observations have been reported from other Gram-negative bacteria (20) and from Rickettsia (21 ). But the experiments also show that the absorbancy increase under otherwise identical conditions is somewhat more pronounced in cp' cells.…”

“…During exposure to hypertonic conditions, it seems that the membranes become increasingly permeable to the solutes tested, and that the cells lose their capacity to maintain an osmotic barrier. In Gram-negative bacteria the exposure to osmotic pressures above 7-8 atmospheres is often connected with plasmolysis, and the spectrophotometric procedure has often been used as a measure of plasmolysis (21,26). It thus seems, that conditions that are generally conductive to more long-lasting plasmolysis is lethal to N .…”

Differences in buoyant-density properties of Coxiella burnetii and Rickettsia rickettsii

“…Differences between Coxiella burnetii and species of the genus Rickettsia were reviewed by Weiss (5), who suggested that the unique stability of C. burnetii may indicate that "leakage does not occur with this microorganism or that lost compounds can be efficiently reacquired in an intracellular environment." Myers et al (2) found that intact R. mooseri cells were impermeable to sucrose, hypertonic NaCl, or hypertonic KCl, but that after being subjected to freezing or lengthy purification procedures these rickettsiae were unable to control the intracellular level of inorganic salts but still retain their impermeability to sucrose. We reported previously (4) that the buoyant density of both formalin-treated and ultraviolet (UV)treated preparations of purified phase I C. burnetii rickettsiae differed from that of untreated rickettsiae in CsCl gradients but were the same as the untreated cells when placed in sucrose gradients; we suggested that this observation might be explained by a permeability difference of the altered rickettsial membrane to sucrose and inorganic salts.…”

Potassium Fluxes on Hyperosmotic Shock and the Effect of Phenol and Bronopol (2‐bromo‐2‐nitropropan‐1,3‐diol) on Deplasmolysis of Pseudomonas aeruginosa

“…Because of the large refractive index of sucrose, an overall reduction in OD occurs with increasing concentrations of sucrose (Myers et al 1967;Kroll 1980).…”