Ribosomal ribonucleic acid synthesis by virulent Treponema pallidum

Inhibition of macromolecular synthesis in cultured rabbit cells by Treponema pallidum (Nichols)

Treponema pallidum partially inhibited the synthesis of DNA, RNA, and protein by rabbit cells in vitro. The inhibition of DNA synthesis was proportional to treponemal concentration and persisted during the period of exposure to T. pallidum. The toxic effect was not dependent on treponemal metabolism or on whole treponemes, since heat- and penicillin-killed treponemes and a cell-free sonicate of treponemes had similar toxicities. The toxic factor(s) was also detected in extracts of syphilitic rabbit testes but not in extracts of normal rabbit testes or testes inflamed by chemical means. The T. pallidum-derived toxic material had a molecular weight greater than 20,000 as determined by dialysis. Protein and DNA synthesis were most rapidly inhibited; RNA synthesis continued at normal rates for up to 2 h after exposure to treponemes. Protein synthesis or a necessary precursor of protein synthesis appeared to be the primary target of the T. pallidum toxin(s).

Restriction analysis of DNA from Treponema pallidum, the causative agent of syphilis

When purified DNA from pathogenic Treponema pallidum is digested with restriction endonucleases it results in the formation of discrete DNA fragments which range between 2.5 to 10 Kilobase pairs. No such precise fragmentation occurs with DNA isolated from nonpathogenic T. pallidum. The appearance of the discrete restriction fragments from the pathogenic T. pallidum DNA does not represent a contamination of satellite DNA from rabbit, the host in which the organism was propagated, but rather represents the presence of redundant DNA or DNA of less complexity in the pathogenic T. pallidum DNA preparation.

Redox potential and survival of virulent Treponema pallidum under microaerophilic conditions

A strongly reduced culture medium, capable of maintaining the virulence of Treponema pallidum (Nichols) for several days, was exposed to an atmosphere of 3% oxygen in nitrogen for 2-3 days before inoculation with T pallidum. By using various volumes of medium in uniform tubes a range of redox potentials (Ecal) from -94 mV to -325 mV was produced depending on the surface area-to-volume ratios of the medium. The anaerobic medium had an Ecal value of -387 mV. The medium was inoculated with T pallidum and incubated in an atmosphere of 3% oxygen. The survival of treponemes at different redox potentials was monitored by observing the retention of motility and by measuring the latent period of infection after inoculation of the cultures into the shaved backs of rabbits. Under these conditions T pallidum survived longest at low (electronegative) redox potential. An inverse linear relationship was observed between the redox potential of the culture medium and the survival of T pallidum, as measured by the time required for a 90% reduction of virulent organisms. No optimum redox potential was detected, the most electronegative medium (-325 mV, Ecal) giving the best survival.

Distribution of glucose incorporated into macromolecular material by treponema pallidum

Treponema pallidum was observed to incorporate glucose carbons into lipids, ribonucleic acid, deoxyribonucleic acid, and protein. Only the glycerol portions of phosphatidylcholine and phosphatidylglycerol contained glucose-derived carbons. Incorporation of exogenous choline into phosphatidylcholine was detected. Glucose was incorporated into only the pentoses of nucleic acids. About 50% of the glucose incorporated into protein was present in only one amino acid, aspartate. Evidence suggests that aspartate synthesis could follow the conversion of phosphoenolpyruvate to oxalacetic acid by a guanosine 5'-diphosphate-dependent phosphoenolpyruvate carboxykinase.

Influence of oxygen on respiration and glucose catabolism by Treponema pallidum

Oxygen consumption by Treponema pallidum was observed to be glucose dependent. Treponemes consumed O2 to a low dissolved O2 concentration of 0.01 mumol of O2 per ml when respiration ceased. A fermentative degradation of glucose occurred during the maintenance of treponemes at 0.01 mumol of O2 per ml. Although the initial rate of respiration was independent of the dissolved O2 concentration, the respiration rate decreased upon prolonged incubation at 0.20 mumol of O2 per ml as compared with the respiration rate at 0.7 mumol of O2 per ml. Oxygen was determined to be the major electron acceptor during the oxidative metabolism of glucose. Acetate formation paralleled the respiration rate of the treponemes, whereas lactate production appeared to be independent of respiration. Accumulation of pyruvate occurred at 0.20 mumol of O2 per ml but not at 0.07 mumol/ml. Analyses of enzyme activities in cell-free extracts from treponemes maintained at either 0.07 or 0.20 mumol of O2 per ml for 4 h revealed a loss of pyruvate decarboxylase activity at the higher dissolved O2 concentration, suggesting the inactivation of pyruvate oxidase.

In vitro cultivation of Treponema pallidum: a review

In vitro cultivation of Treponema pallidum would facilitate many different aspects of syphilis research. This review summarizes developments in this field that have been published since 1975. Findings are discussed in terms of treponemes and the oxygen question, treponemal metabolism involving proteins, nucleic acids, and fatty acids, and treponemal interaction with tissue culture cells. Suggested future approaches and potential problem areas pertinent to successful cultivation are discussed.

Long-term incorporation of tritiated adenine into deoxyribonucleic acid and ribonucleic acid by Treponema pallidum (Nichols strain)

Treponema pallidum (Nichols strain), extracted in medium containing Eagle minimal essential medium 50% fresh, heat-inactivated normal rabbit serum, and 1.0 mM dithiothreitol, was incubated under 3% oxygen in the presence of tritiated nucleic acid precursors. [8-3H]adenine was incorporated with high efficiency into trichloroacetic acid-insoluble material; 2'-deoxyadenosine and uridine were incorporated in lower quantities, and thymine and thymidine were not incorporated. Incorporation of [3H]adenine was inhibited by penicillin G, mitomycin C, actinomycin D, and erythromycin, but was not affected by cycloheximide. Partial purification of nucleic acids from T. pallidum incubated with [8-3H]adenine for 36 to 72 h and subsequent treatment with ribonuclease and deoxyribonuclease revealed that 15 to 20% of the trichloroacetic acid-precipitable counts were resistant to ribonuclease but susceptible to deoxyribonuclease. A simple assay was developed in which NaOH treatment was used to distinguish incorporation into ribonucleic acid and deoxyribonucleic acid. Both ribonucleic acid and deoxyribonucleic acid synthesis continued for 6 days of incubation under 3% O2, whereas incorporation was limited to the first day of incubation in samples incubated under aerobic or anaerobic conditions. T. pallidum thus appears to be capable of significant de novo deoxyribonucleic acid and ribonucleic acid synthesis under microaerobic conditions.

Surface-associated host proteins on virulent Treponema pallidum

A surface coat of host serum proteins was detected on virulent Treponema pallidum by sodium dodecyl sulfate-gel electrophoresis. The loosely associated serum proteins could be removed by repeated washings in a protein-free medium. Washed T. pallidum retained the ability to readsorb numerous host proteins from rabbit serum as well as iodinated rabbit or human albumin. In addition, various avidly associated host serum proteins including albumin, alpha(2)-macroglobulin, transferrin, ceruloplasmin, immunoglobulin G, immunoglobulin M, and C3 were identified on the outer envelope of washed treponemes by an immunoadsorbent technique with protein A-bearing staphylococcus. Hyaluronidase treatment did not remove the avidly associated host proteins from the surface of washed treponemes, whereas trypsin treatment resulted in decreased levels of agglutination. Electrophoretic patterns of trypsin-treated treponemes showed that treponemal proteins as well as adsorbed host proteins were released concurrently by protease digestion. Reacquisition studies involving alpha(2)-macroglobulin and transferrin suggested the presence of noncompetitive binding sites for serum proteins on the treponemal outer envelope. Finally, differences among the T. pallidum preparations from individual rabbits with respect to incorporation of [(35)S]methionine, extent of agglutination with antisera, and length of time required for removal of avidly associated host proteins by trypsin treatment indicated biological variability among the treponemal populations.

Optimum concentration of dissolved oxygen for the survival of virulent Treponema pallidum under conditions of low oxidation-reduction potential

A maintenance medium with a low oxidation-reduction (redox) potential, when gently bubbled with 5% oxygen in nitrogen or with air for various periods of time, gave a range of dissolved oxygen concentrations between 1.6 and 5.8 micrograms/l. Virulent Treponema pallidum (Nichols strain) inoculated into these media were assayed 24 and 48 hours later for motility and virulence and were compared with samples taken at zero time. Virulent T. pallidum survived best in the presence of 2.4 micrograms/l dissolved oxygen over a 48-hour period, which corresponded to a gaseous mixture of 3% oxygen in nitrogen. Higher concentrations of oxygen did not give significantly different results from anaerobic conditions over this period. Thus, until it can be grown in vitro, T. pallidum would appear to be a microaerophilic bacterium.

Glucose incorporation by Treponema pallidum

Treponema pallidum incorporated glucose into trichloroacetic acid-precipitable material. The amount of incorporation was proportional to the number of treponemes and was estimated to equal 3% of the glucose oxidized.

Capacity of virulent Treponema pallidum (Nichols) for deoxyribonucleic acid synthesis

Treponema pallidum (Nichols) was extracted from infected rabbit tissue, and cell lysates were prepared for monitoring thymidine kinase and deoxyribonucleic acid polymerase activities. No thymidine kinase could be demonstrated in preparations of T. pallidum or the cultivable T. phagedenis biotype Reiter. Significant levels of deoxyribonucleic acid polymerase were detected in both treponemal samples. Interestingly, comparisons of polymerase activity among a spectrum of bacterial genera revealed a direct correlation between enzyme concentrations and estimated generation time. Incorporation of [3H]uridine and [3H]thymidine into macromolecules by intact T. pallidum and the Reiter treponeme was examined. Selective ribonuclease-deoxyribonuclease digestion and cesium chloride gradient banding demonstrated that T. pallidum, independent of the host, and T. phagedenis were capable of synthesizing deoxyribonucleic acid only from the [3H]-uridine precursor.

Influence of oxygen tension, sulfhydryl compounds, and serum on the motility and virulence of Treponema pallidum (Nichols strain) in a cell-free system

The motility and virulence of Treponema pallidum (Nichols strain) were monitored during incubation in a modified tissue culture medium to study the effects of oxygen tension and medium composition on survival of the organism. A basal medium of Eagle minimal essential medium with 50% fresh, heat-inactivated normal rabbit serum was used inasmuch as better survival occurred with 50% normal rabbit serum than with lower concentrations. Addition of 0.5 to 2.0 mM dithiothreitol or 2.0 mM dithioerythritol to the basal medium led to significantly longer retention of T. pallidum viability in the presence of 3% oxygen than under aerobic or anaerobic conditions. The results of this investigation lend support to the classification of T. pallidum as a microaerophilic organism and provide direction for the design of potentially successful culture systems, with or without tissue culture cells.

Radiolabeling of Treponema pallidum (Nichols virulent strain) in vitro with precursors for protein and RNA biosynthesis

We observed uptake of [U-14C]serine, U-14C-labeled amino acid hydrolysates, and [2-14C]uracil by virulent Treponema pallidum in vitro for at least 96 h. No uptake of [2-14C]thymine, [1-14C]pyruvate, [U-14C]pyruvate, and [2-14C]uridine was detected. Treponemal protein and RNA biosynthetic activity was identified by erythromycin inhibition of amino acid and uracil uptake. Radioactivity due to uptake of radiolabeled amino acids by residual testicular cells in the cultures remained at background levels regardless of the presence or absence of cycloheximide. Accumulation of the radiolabeled substrates by T. pallidum proceeded at a linear rate for 48 to 96 h during incubation in vitro. The longevity of substrate uptake using the system of incubation described will facilitate future studies on the metabolism of the microorganism to help determine essential growth factors and environmental conditions for multiplication of T. pallidum in vitro.