Glucosylation of Teichoic Acid: Solubilization and Partial Characterization of the Uridine Diphosphoglucose:Polyglycerolteichoic Acid Glucosyl Transferase from Membranes of Bacillus subtilis

Polyglycerolteichoic acid:glucosyl transferase (TAG transferase), one of the three enzymes involved in the pathway leading to the glucosylation of teichoic acid in Bacillus subtilis 168, was investigated. During the early stages of the growth of B. subtilis, TAG transferase is predominantly a soluble enzyme found in the cytoplasm. As growth proceeds, the amount of soluble enzyme decreases and the proportion of insoluble, membrane-bound TAG transferase increases, reaching a maximal value at the close of the logarithmic phase. Data are presented which suggest that these are two forms of the same enzyme, or have some common component. The effects of chaotropic agents, such as sodium trichloroacetate and sodium perchlorate, on the cytoplasmic membrane were also studied. These data show that such compounds can effectively remove the TAG transferase from the membrane in a water-soluble form. A study of some of the physical properties of this solubilized enzyme suggests that there is little difference between the two forms of the enzyme. Experiments are described which indicate that the glucosyl transfer by both the membrane-bound and soluble enzymes is not mediated by lipids.     

A STUDY OF GLUCO-CORTICOSTEROID-INDUCED PYKNOSIS IN THE THYMUS AND LYMPH NODE OF THE ADRENALECTOMIZED RAT

Pyknotic nuclei, observed in the thymus of steroid-treated rats, are dense, homogeneous, intensely basophilic and Feulgen positive. Under the electron microscope, the image is that of a complete segregation of the chromatin from the nuclear sap producing a margin or crescent of condensed chromatin. Approximately 30% of all small thymocytes appeared to undergo this type of degeneration within 3–4 hr after administration of the synthetic corticosteroid, dexamethasone. At this time, pyknotic thymocytes were observed in clusters, probably as a result of the activity of dense reticular cells and macrophages. Topographical and experimental data suggest the existence of a select population of steroid-sensitive thymic cells. Furthermore, on the basis of thymidine-³H incorporation studies, it appears that the steroid-sensitive population of thymocytes does not correspond to "aged" cells. In addition, many plasma cells became pyknotic after the same steroid treatment, indicating an unexpected similarity between their nuclei and those of lymphocytes. Finally, steroid failed to induce pyknosis of thymocytes in a variety of in vitro experiments, suggesting that the in vivo effect of steroid is of an indirect nature. The results are discussed in terms of (a) the nature of the nuclear changes characterizing pyknosis, (b) the hypothetical mechanism whereby steroids trigger such changes, and (c) the population of cells susceptible to steroid-induced pyknosis.     

Salt injury to plants with special reference to cations versus anions and ion activities

Summary In contrast with the toxicities of sulfate and chloride salts added to substrates, the anions SO₄ and C1 were not injurious when accumulated without leaf burning by cotton and tomato plants from atmospheres enriched with SO₂ or HC1 gases. The foregoing results are discussed in terms of cationenzyme interactions which appear to represent at least a major cause of salt toxicity. Although anions are largely unreactive with enzymes it has long been observed that chloride salts in soil solutions are far more toxic than sulfate salts. Five of seven species have shown nearly equal growth repressions on substrates with 100 me/1 of C1 salts versus 200 me of SO₄ salts, each added as 50 per cent Na. The ion activities of the two solutions were equal and the sum of cations in the plant saps were similar. The osmotic differentials (average about 10 atm) between the expressed tissue fluids and these substrate solutions were remarkably uniform within species. It is projected that the downward transport of salts via the phloem provides for root concentrations which supply ions to the xylem and thereby control the uptake of substrate salts.     

Inhibition of Transformation of Bacillus subtilis by Heavy Metals

Mercuric ions, as well as organomercuric ions and cadmium ions, can inhibit deoxyribonucleic acid-mediated transformation in Bacillus subtilis 168 without decreasing the viability of the total population. Differences in the inhibition of transformation by mercuric ions are identifiable on a temporal and concentration dependence basis. Sensitivity to low concentrations (9.2 x 10(-8) M) appears early in the uptake of deoxyribonucleic acid before the transformed markers have become insensitive to deoxyribonuclease. Resistance to "low concentrations" of Hg(2+) is kinetically indistinguishable from the requirement for magnesium in the transformation process. This inactivation is not reversed by the mercury-binding compound glutathione. Sensitivity to mercuric ions at a higher concentration (5.52 x 10(-7) M) occurs after the donor deoxyribonucleic acid has become insensitive to deoxyribonuclease. These complex interactions between mercuric ions and the process of transformation are discussed.     

Mutation in Saccharomyces cerevisiae Conferring Streptomycin and Cold Sensitivity by Affecting Ribosome Formation and Function

A cold-sensitive, streptomycin-sensitive mutant of Saccharomyces cerevisiae accumulates a 28S ribonucleoprotein particle when grown at low temperature. This particle contains 17S ribosomal ribonculeic acid which is degraded when exposed to ribonuclease. The particle does not serve as a precursor to 60 and 40S ribosomal subunits nor is it turned over when growth is allowed to resume at the permissive temperature; rather it is only diluted by growth. That streptomycin sensitivity (allelic with cold sensitivity) is ribosomal is evidenced by the inhibition of protein synthesis in vitro by streptomycin and the binding of labeled streptomycin to the mutant but not the parental 40S ribosomal subunit.