Presence of ribosomal ribonucleic acid in the rickettsia Coxiella burneti

Isolation and characterization of a plasmid from phase I Coxiella burnetii

The DNA from the Nine Mile phase I strain of Coxiella burnetti, the etiological agent of Q fever, has been isolated and purified by cesium chloride-ethidium bromide density gradient centrifugation. A fraction of this DNA has a density characteristic of plasmid DNA. The plasmid DNA was cut with 20 different restriction endonucleases and shown to be a discrete entity. The plasmid, designated QpH1, is approximately 36 kilobases in size and has a molecular mass of 2.4 x 10(7) daltons. A partial restriction map of QpH1 has been constructed by using the restriction endonucleases SalI, KpnI, PstI, and XbaI. QpH1 DNA radioactively labeled by nick translation was used to show that sequences similar to the plasmid are also present in the phase II antigenic variant of C. burnetii.

Q fever and Coxiella burnetii: a model for host-parasite interactions

Images

Purification of Rickettsia tsutsugamushi by Percoll density gradient centrifugation

Purification of Rickettsia tsutsugamushi has been achieved by Percoll density gradient centrifugation. The microorganisms purified showed good retention of infectivity and intracellular morphology. Budding rickettsiae in the egressing stage and intracellular rickettsiae in the multiplying process were harvested separately and purified by this technique. In electron microscopic observations, the intracellular rickettsiae obtained were surrounded with double membrane-layers of cell wall and cell membrane, and the budding rickettsiae were enveloped with an additional outermost membrane which may have originated from host cell membrane obtained in the budding process.

Efficacy of translation in the rickettsia Coxiella burnetii

The addition of coliphage Q beta ribonucleic acid to a cell-free translation system obtained from Coxiella burnetii cells caused the formation of monosomes and disomes from ribosomal subunits and resulted in synthesis of viral coat protein. Rickettsial ribosomes and associated translation factors functioned together, with fidelity, efficiency, and a specificity similar to those of free-living gram-negative bacteria.

Genome size of the rickettsia Coxiella burnetii

The genome size of Coxiella burnetii Nine Mile strain was determined by the method of initial rate of deoxyribonucleic acid renaturation. The mean value obtained was 1.04 X 10(9) daltons.

Synthesis of ribonucleotides and their participation in ribonucleic acid synthesis by Coxiella burnetii

Synthesis of ribonucleic acid (RNA) by the deoxyribonucleic acid-dependent RNA polymerase of Coxiella burnetii required adenosine, uridine, guanosine, and cytidine 5'-triphosphates. Cell-free preparations of this obligate intracellular procaryotic parasite had competence to phosphorylate ribonucleoside mono- and diphosphates in the presence of exogenous adenosine and guanosine 5'-triphosphates to the corresponding di- and triphosphates. C. burnetii contained about 2 nmol of adenosine 5'-triphosphate per mg of protein, which could serve as a approximately P donor for in vivo synthesis of nucleoside triphosphates. The latter were then used as substrates in the synthesis of RNA in a coordinated metabolic system with C. burnetii RNA polymerase. It is suggested that during infection the rickettsiae might obtain the nucleotides necessary for RNA synthesis from the vacuoles in which C. burnetii proliferates.

Further characterization of a lipopolysaccharide from Coxiella burneti

The lipopolysaccharide previously isolated from the rickettsial agent of Q fever, Coxiella burneti, phase I, has been further characterized. The sugar residues ribose, mannose, gluclose, D-glycero-D-mannoheptose, and L-glycerto-D-mannoheptose are present. Two sugars remain unidentified, one of which is a minor and the other a major constituent. Isomyristic, palmitic, and beta-hydroxymyristic acids are the major fatty acid residues of the 15 identified. The nature and content of other lipopolysaccharide constituents are presented.

Separation of viable Rickettsia typhi from yolk sac and L cell host components by renografin density gradient centrifugation

Rickettsia typhi cultivated in the yolk sac of chicken embryos or in L cells irradiated 7 days previously was separated from host cell components by two cycles of Renografin density gradient centrifugation. Preliminary steps involved differential centrifugation and centrifugation over a layer of 10% bovine plasma albumin of infected yolk sac suspensions, or trypsinization and passage through filters of wide porosity of infected L cell suspensions. Rickettsial preparations obtained by these methods appeared to be free from host cell components while retaining high levels of hemolytic activity, egg infectivity, and capacity to catabolize glutamate. Average yields were 3.3 mg of rickettsial protein per yolk sac or 0.44 mg per 16-oz (ca. 475-ml) L cell culture. Extracts from these two preparations displayed malate dehydrogenase activity of electrophoretic mobility identical to each other but quite different in migration patterns from the corresponding host cell enzymes. This method of separation of rickettsiae from host cell constituents appears to be particularly well suited for the study of rickettsial enzymatic activity.

Electron microscopy studies of the limiting layers of the rickettsia Coxiella burneti

Surface layers of Coxiella burneti studied at a high resoulution reveal a plasma membrane and an outer surface membrane 6 to 7 nm thick, and a thin, moderately electron-dense intermediate layer associated with the inner surface of the outer membrane of many cells. This layer appears to be unaffected by lysozyme treatment. Ruthenium red staining was used to delineate a layer of filamentous material external to the outer membrane; this fuzzy layer has a mean thickness of 20 nm and is not often seen on the surface of cells prepared by conventional means. Both antigenic phase I and II cells show a ruthenium red-binding surface layer. It is suggested that this fuzzy layer may be, among other possibilities, a highly branched mucopolysaccharide.

Some physiological and biochemical effects of a Coxiella burneti lipopolysaccharide preparation on guinea pigs

A lipopolysaccharide obtained in a dialyzed phenol extract from the rickettsia Coxiella burneti produced the following effects in guinea pigs after intraperitoneal injection: hyperthermia, loss of body weight, increased liver weight and concomitant lipid infiltration, elevated levels of hepatic and plasma cortisol, increased incorporation of [(3)H]orotic acid into hepatic 28S and 18S ribosomal ribonucleic acid, increased incorporation of (14)C-labeled amino acids into liver and plasma protein, and leukocytosis. Most of these events also occur during infection of guinea pigs with C. burneti, and a causal relationship between the rickettsial lipopolysaccharide and the biochemical changes that occur during Q fever is suggested.

Ribosomes and ribonucleic acids of Coxiella burneti

This report describes the direct isolation and characterization of rickettsial ribosomes. Ribosomes from the rickettsia Coxiella burneti were isolated and partially characterized. The ribosomes had a sedimentation constant of about 70S and could be dissociated into 50 and 30S subunits. Electron microscopy revealed ribosomal particles with dimensions similar to those reported for other procaryotic organisms. Ribonucleic acid (RNA) species (23 and 16S) were isolated from the ribosomal particles. The nucleotide compositions of the ribosomal RNAs were found to be similar to those reported for bacterial ribosomal RNA. In addition to the high-molecular-weight ribosomal RNA, 5S RNA was also extracted from the organism.

Growth and physiology of rickettsiae

Images

Ribonucleic acid and protein synthesis in guinea pig liver during Q fever

Protein and ribonucleic acid (RNA) syntheses increase in the liver during Q fever, coincident with progressive increments in cortisol levels. Cell-free protein-synthesizing systems indicate that the pH 5 enzyme fraction was chiefly responsible for enhanced activity. Although the polysome profiles from normal and infected livers were similar, the number of liver ribosomes doubled during infection. There was a concomitant increase in orotate incorporation in the 28s, 18s, and 4s RNA species of infected liver.