Rhapidosomes: 2'-O-methylated ribonucleoproteins

Methylation of the RNA component from seven flexibacterial rhapidosomes varied in extent, distribution along the RNA chain, and distribution between nucleotides. Flexibacterial soluble and ribosomal RNA had normal (low) methylation.

Involvement of protein and ribonucleic acid in the association of deoxyribonucleic acid with other cell components of Escherichia coli

Cells of Escherichia coli were labeled with precursors of ribonucleic acid (RNA), deoxyribonucleic acid (DNA), and protein, lysed with detergent, and examined by starch-block electrophoresis and CsCl density gradient centrifugation. A large amount of the DNA was seen to remain at positions of low electrophoretic mobility and light density along with tryptophan and arginine-containing proteins and some RNA. Addition of labeled, phenol-extracted DNA to unlabeled cells prior to lysis and electrophoresis showed that only a small amount of the DNA became associated during or after lysis. Sonic treatment of a lysate removed most of the DNA to a position of electrophoretic mobility and density similar to that of free DNA, whereas pronase and ribonuclease released only a part of the DNA. We concluded that binding of DNA to cell membranes or other cell components occurs in the cell prior to lysis and involves protein and probably a specific type of RNA.

Ribonucleic acid synthesis in T2-infected Escherichia coli during "stringent" control

The leucine auxotroph Escherichia coli 2961 exhibited stringent control of net ribonucleic acid (RNA) synthesis during amino acid starvation. After leucine was exhausted from the medium, the rate of uracil incorporation into RNA rapidly decreased to 2 to 4% of the prestarvation value. Infection of the starved cells with T2 phage stimulated uracil incorporation to a level equivalent to that of unstarved, T2-infected cells. The RNA synthesized during leucine starvation of the T2-infected cells consisted of T2 and E. coli messenger RNA, but stable ribosomal RNA (23S and 16S) did not appear to be synthesized. It is concluded that one or more T2-specific proteins are required to shut off host messenger RNA synthesis. Furthermore, transcription of E. coli and T2 deoxyribonucleic acid is not necessarily coupled to the translation of messenger RNA during stringent control of net RNA synthesis.

Studies on the role of polyamines associated with the ribosomes from Bacillus stearothermophilus

1. Spermine and spermidine were the main polyamines detectable in Bacillus stearothermophilus. 2. When grown at 65 degrees B. stearothermophilus contained lower concentrations of polyamines per mg. of RNA than when grown at 45 degrees or at 55 degrees . 3. Ribosomes isolated from B. stearothermophilus in 0.01m-tris-hydrochloric acid buffer (pH7.4)-0.01m-magnesium chloride contained sufficient polyamines to neutralize between 4% and 9% of their RNA phosphorus. 4. Removal of polyamines from the ribosomes by dialysis against m-potassium chloride did not appreciably alter the hypochromicity or thermal denaturation profiles of the ribosomes when measured in 0.01m-tris-hydrochloric acid buffer (pH7.4)-0.01m-magnesium chloride, though it did cause a loss of ribosome particles sedimenting at greater than 78s. 5. When ribosomes were dialysed against acridine orange solutions acridine orange bound to the ribosomes and did not displace spermine, but when a mixture of ribosomal RNA and spermine was dialysed against acridine orange the acridine orange displaced the spermine. It is concluded that polyamines in the ribosomes are less accessible for displacement by acridine orange than when polyamines are bound to ribosomal RNA.

Mitomycin C induction of a temperate phage in Pseudomonas aeruginosa

After addition of mitomycin C to Pseudomonas aeruginosa strain MAC-264 cells, DNA synthesis stops but resumes again after 45 min. This resumption in DNA synthesis is due to the induction of a temperate phage. Early after induction, both RNA and protein syntheses continue but later on little or no net synthesis of these macromolecules occurs. Cell lysis occurs at 90 to 105 min after addition of mitomycin C. Analysis of the lysates indicates that a DNA phage with an icosahedral head about 55 mμ in diameter with a short wedge-shaped tail is produced. This phage [Formula: see text] has a buoyant density of 1.468 g/ml in CsCl. The guanine + cytosine content of the phage DNA determined by its buoyant density in CsCl is 46% compared to 68% for the host DNA.Some phage tail-like structures which have a buoyant density of 1.305 g/ml in CsCl are also induced at the same time.

Survival and intracellular changes of Pseudomonas aeruginosa during prolonged starvation

The viability of suspensions of Pseudomonas aeruginosa, prepared from 48-h cultures, grown in either a nitrogen-limited or carbon-limited medium, decreased 25% during 48-h of endogenous respiration, whereas the viable numbers of 48-h cells harvested from a complete medium increased 57% during the early stages of endogenous respiration and remained constant thereafter. In all endogenously respiring cell suspensions, ribonucleic acid and protein decreased by similar amounts and deoxyribonucleic acid increased. Glucosamine was not found to decrease to a significant degree during starvation. Constitutive enzymes and (or) the cofactors involved in the oxidation of glucose were found to diminish with progressive starvation. Starvation severely depleted the ribosome complement of the cells; however, the starved cells were able to synthesize a permease for α-ketoglutarate. The addition of an exogenous substrate brought about the reincorporation of endogenously liberated ammonia and of 260 mμ absorbing material with a concurrent synthesis of 50S ribosomes.

The temperature optimum of the intestinal flora of the rat

Two types of experiments were performed to determine if the microbial flora of the intestinal tract of the rat was optimally adapted to body temperature. The first involved the preparation of agar-spread plates from dilutions of intestinal material and incubation at a variety of temperatures. The temperature optima of the colonies which arose were then determined by replica plating. The second procedure involved the measurement of the temperature optimum for the incorporation of radioactive isotopes into the mixed microbial flora taken directly from the intestinal tract and studied without culture or preincubation. One series of experiments involved measurement of the rate of incorporation of 32PO4≡ into ribonucleic acid and deoxyribonucleic acid. In another set of experiments, the temperature optimum for the incorporation of 14C-glucose into the mixed microbial flora was measured. All of these studies showed that the optimum temperature of the microbial flora was indeed similar to the temperature of the habitat. Preliminary studies were also done with a dog and with red squirrels, with similar results.

Nucleic acid methylase activity in hamsters bearing tumors induced by adenovirus-12

Cell-free extracts of tumor cells induced by adenovirus-12 derived from Syrian hamsters possessed higher transfer RNA (tRNA) methylase activity than cell-free extracts from liver, lung, kidney, spleen, or skin and muscle. No difference was found between normal and tumor cell free extracts in the methylation of DNA or ribosomal RNA.The tRNA methylase activities in cell-free extracts from hamster embryos were in the range found for normal adult tissue extracts. It appears therefore that the increase in tRNA methylase is characteristic of the tumor cells, and is not a result of their rapid growth.

Effect of chloramphenicol on the synthesis and stability of ribonucleic acid in Bacillus subtilis

The effect of chloramphenicol on the synthesis and accumulation of ribonucleic acid (RNA) in Bacillus subtilis was studied. In the presence of chloramphenicol, transfer RNA and ribosomal RNA were synthesized as rapidly 2 to 3 hr after challenge as they were just prior to the addition of the antibiotic. However, under the same conditions, net RNA accumulation ceased after only 30 to 45 min. The failure to accumulate RNA after this time resulted from a rapid degradation of ribosomal RNA synthesized in the presence of chloramphenicol and a slow degradation of mature ribosomes. Since transfer RNA was not appreciably degraded, the ratio of transfer RNA to total RNA increased during the challenge.

Synthesis of protein and ribonucleic acid in a psychrophile at normal and restrictive growth temperatures

A defined medium was capable of supporting the growth of a psychrophilic coccus over its growth temperature range, -4 to 25 C. A rapid loss of viability occurred when exponential cells were transferred to growth-restricting temperatures above 25 C. Comparative studies of the chemistry of exponential-phase cells and cells exposed to supermaximum temperature indicated that this loss of viability is not due to temperature-induced membrane damage, inhibition of respiration or energy metabolism, or depletion of intracellular reserves. Moribund and dead cell populations showed an elevated level of intracellular adenosine-5'-triphosphate and amino acids-a finding reflected in the reduced rate of amino acid synthesis during the recovery of heat-shocked cells-and also leakage of degraded ribonucleic acid products into the medium. Incorporation studies indicated that loss of viability at 30 C was correlated with inhibition of protein synthesis, followed later by inhibition of ribonucleic acid synthesis. Deoxyribonucleic acid synthesis was unaffected by temperature above the maximum.

Separation of bacterial ribosomal ribonucleic acid from its macromolecular precursors by polyacrylamide gel electrophoresis

Electrophoresis on polyacrylamide gels was found to be a powerful technique for separating the mature from the precursor forms of bacterial ribosomal nucleic acid (rRNA). The separation of the 16S rRNA from its precursor was, for all practical purposes, complete; that of the 23S rRNA from its precursor was detectable but incomplete. When mature and precursor rRNA preparations were heated to randomize secondary structure, etc., and then cooled, it was found that electrophoretic mobility differences between mature forms of rRNA and their precursors persisted. This, in conjunction with the rather large electrophoretic mobility differences between mature and precursor forms, can be taken as strong evidence for a molecular weight difference between mature rRNA and its precursor forms of RNA. With the 16S rRNA, this difference could be as large as 130,000 daltons.

Metabolic events occurring during recovery from prolonged glucose starvation in Escherichia coli

The effects of starving Escherichia coli for glucose and required amino acids were determined. The disappearance of the majority of the ribosomal population, particularly of the ribonucleic acid (RNA) moiety, was noted. The events during recovery are detailed, with emphasis placed on the timing, requirements, and control of deoxyribonucleic acid, RNA, and protein synthesis and on ribosome reassembly. Finally, the applicability of the system to the study of temperature-sensitive mutants is documented and discussed.

Thermally induced ribonucleic acid degradation and leakage of substances from the metabolic pool in Staphylococcus aureus

The effects of temperatures of 50 and 60 C on log-phase and stationary-phase cell suspensions of Staphylococcus aureus are described. There is a leakage of free amino acids, protein, and 260 mmu-absorbing material from both types of cell suspension, and membrane damage, as measured by the intracellular penetration of 8-anilino-1-naphthalene-sulfonic acid, may be partially related to this leakage. Ribonucleic acid (RNA) degradation at any one temperature is virtually the same for both types of cell suspension, proceeding initially at a more rapid rate at 60 C than at 50 C. However, at the lower temperature, there is a secondary breakdown of RNA, which may be the result of enzyme action on a particularly labile RNA fraction. With stationary-phase cell suspensions heated in 1 m sucrose, there is a more rapid degradation of RNA at 60 C than with cells in water. The results are discussed in relation to the biochemical effects of moist heat on the organism.