Energy-linked light-scattering changes in Escherichia coli

Effect of antineoplastic and cytotoxic Mannich Bases derived from conjugated styryl ketones on mitochondrial respiration in rat liver cells

Five cytotoxic Mannich bases (5-dimethylamino-1-substituted phenyl-1-penten-3-ones), three having antineoplastic activity, were evaluated for respiratory-inhibiting properties in rat liver mitochondria in the presence of four substrates: succinate, glutamate, 3-hydroxybutyrate, and palmitylcarnitine. Four compounds (Ib--Ie) showed significant inhibiting properties which, on occasion, were reversed partially by coenzyme Q10. Evaluation of the spectra of the mitochondrial cytochromes indicated that Ib--Ie blocked the electron transport chain prior to the sequence of cytochromes. Since inhibition occurred when different substrates were used, a common site of action for Ib--Ie is likely; competition of Ib--Ie with coenzyme Q10 probably occurs. Compounds Ia--Ie inhibited RNA polymerase from Swiss mouse kidney cells but were virtually bereft of activity versus RNA polymerase from L-1210 leukemia cells. Polarography of the Mannich bases and the related styryl ketones showed that antineoplastic activity was associated with higher half-wave potentials.

Betaine-induced stimulation of respiration at high osmolarities in a halotolerant bacterium

It was shown that non-penetrating solutes at high concentrations inhibit the respiration of the halotolerant bacterium Ba1. Betaine relieved the inhibition caused by osmotic stress and exhibited in this respect a considerable structural specificity. The rate of oxidation of various substrates was stimulated to different extents. It stimulated the rates of both respiration and growth to a similar extent, leaving the energy yield essentially unchanged. In cells pre-loaded with labelled glutamate, betaine also stimulated the rate of oxidation of this intracellular substrate. Betaine was accumulated by respiring cells, and the maximum amount taken up was correlated with the osmolarity of the medium. As judged by chromatography, accumulated intracellular betaine underwent no chemical modification, and this accumulated betaine could not be exchanged with the betaine in the medium or released by passive efflux when respiration was inhibited. Intracellular betaine caused no stimulation of respiration, whereas betaine added to the medium increased the respiratory rate to the same extent in cells pre-loaded with betaine as that in the nonloaded cells. The above observations suggest that iso-economic adjustment is not involved in the anti-osmotic effect of betaine, and that betaine exerts its action on the cellular membrane from the outside.

Conservation and transformation of energy by bacterial membranes

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Response of Escherichia coli B-r to high concentrations of sucrose in a nutrient medium

Escherichia coli B/r was subjected to sucrose concentrations up to 1 m in the presence of Nutrient Broth. Plasmolysis seldom was evident 2 min after this treatment. The subsequent response was characterized by transient decreases in optical density as well as changes in appearance as seen under phase optics. No transient effects were detected in the synthetic rates or in the division of the survivors.

Nitrate reductase and soluble cytochrome c in Spirillum itersonii

The addition of nitrate to cultures of Spirillum itersonii incubated under low aeration produced a diauxic growth pattern in which the second exponential phase was preceded by the appearance of nitrite in the medium. The organism also grew anaerobically in the presence of nitrate. Nitrate reductase activity could be demonstrated in cell-free extracts by use of reduced methyl viologen as the electron donor. The enzyme was located in the supernatant fraction after centrifugation of extracts for 2 hr at 40,000 x g, and it sedimented as a single peak when centrifuged in a sucrose gradient. Nitrate reductase activity was found in cells grown with low aeration without nitrate, but was increased about twofold by addition of nitrate. Enzyme activity was negligible in cells grown with high aeration. The proportion of soluble cytochrome c was increased two- to threefold in cells grown with nitrate. The specific activities of nitrate reductase and soluble cytochrome c rose when nitrate or nitrite was added to cell suspensions incubated with low aeration; nitrite was more effective than nitrate during the early stages of incubation. A nitrate reductase-negative mutant synthesized increased amounts of soluble cytochrome c in response to nitrate or to nitrite in the cell suspension system. It is concluded that enhanced synthesis of soluble cytochrome c does not require the presence of a functional nitrate reductase.

Mechanism of optical effects in suspensions of a marine pseudomonad

When cells of a marine pseudomonad washed free of medium components with 0.05 m MgSO(4) were suspended in solutions containing 200-mm concentrations of various salts, there was an immediate increase in optical density (OD), followed by a slow decrease. The decrease following the initial increase, but not the increase itself, could be prevented by omitting K(+) from or by adding metabolic inhibitors to the suspending solution. With NaCl, the initial increase in OD rose to a maximum as the salt concentration was increased to 200 mm and then declined at 500 mm. There was a corresponding decrease in intracellular fluid volume to a minimum at 200-mm NaCl and then a rise. When the increased OD produced by NaCl was maintained, the internal Na(+) and Cl(-) could be shown to have reached essentially the same concentration in the cells as in the medium. Thus, the OD changes could not have been due to osmotic effects. No evidence was obtained of a salt-induced aggregation of nuclear material. The OD of suspensions of isolated cell envelopes increased in response to increases in NaCl concentration in the absence but not in the presence of 0.05 m MgSO(4). The data was interpreted to indicate that the salt-induced increases in OD occurring in suspensions of the cells resulted from an interaction of salts with components of the cell envelope, causing contraction of the envelopes and shrinkage of the cells.

Differential light scattering: a physical method for identifying living bacterial cells

Differential light scattering techniques appear to represent an attractive physical method for the rapid identification of various microorganisms. Certain general results of inverse scattering theory suggest strongly that characteristic of each distinct microorganism that scatters light is an essentially unique scattering pattern, i.e., unique differential scattered intensity and polarization. Although a mathematically rigorous inversion procedure seems impractical at this time, the use of detailed differential scattered intensity data as an identification fingerprint shows considerable. promise. Published measurements on nonbiological scatterers confirm this possibility. A variety of calculations are presented that contrast the expected scattering characteristics of certain microorganisms such as Bacillus subtilis, B. anthracis, Staphylococcus epidermidis, S. aureus, Escherichia coli, and the spores of B. mcgaterium and B. cereus. Experimental and instrumentation difficulties and possible procedures are discussed. A review and laboration of some applicable features of Rayleigh-Gans scattering are included as an appendix.

FACTORS WHICH MODIFY THE EFFECT OF SODIUM AND POTASSIUM ON BACTERIAL CELL MEMBRANES

Henneman, Dorothy H. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Factors which modify the effect of sodium and potassium on bacterial cell membranes. J. Bacteriol. 87:1266-1273. 1964.-Suspensions of Escherichia coli B, when placed in 0.2 to 0.5 m solutions of NaCl, KCl, or LiCl, show an increased turbidity. With NaCl, this increased turbidity is stable with time; with KCl and LiCl, it is gradually lost. The stability to NaCl with time is due to substances removable from the cell by incubation in phosphate buffer; these materials exist in water washings from such phosphate-incubated cells.

INFLUENCE OF THE PHYSICAL STATE OF THE BACTERIAL CELL MEMBRANE UPON THE RATE OF RESPIRATION

Henneman, Dorothy H. (Rutgers, The State University, New Brunswick, N.J.), and W. W. Umbreit. Influence of the physical state of the bacterial cell membrane upon the rate of respiration. J. Bacteriol. 87:1274-1280. 1964.-NaCl and KCl in concentrations of the order of 0.2 to 0.5 m inhibit the respiration of Escherichia coli B and other gram-negative organisms. Cell-free enzymes concerned in respiration and prepared from the same organisms are not inhibited by these salts, whereas these same enzymes tested in intact cells are. The physical state of the cell membrane appears to be a factor controlling its respiratory activity.

TURBIDITY CHANGE DURING GLUCOSE PERMEATION IN ESCHERICHIA COLI

Rogers, Dexter (Utah State University, Logan) and Shon-Hua Yu . Turbidity change during glucose permeation in Escherichia coli . J. Bacteriol. 85: 1141–1149. 1963.—In contrast to the normal turbidity decrease, which was observed at pH 5.5, the turbidity of suspensions of Escherichia coli strain A (Weigle) increased during uptake of glucose permease substrates when uptake was studied at pH 6.5. Although the turbidity increase at pH 6.5 was the reverse of the expected change, it correlated with the uptake of substrate. During the later phase of permeation at pH 6.5, both uptake of substrate and turbidity change were reversed. We suggest that the observed turbidity response indicated the accumulation of substrate at the cell membrane when the mechanism for releasing substrate to the cytoplasm was inhibited at pH 6.5. Under this condition, uptake of substrate did not cause swelling because the substrate was osmotically inactive, since it may have been bound to the membrane. Permeability was observed to be susceptible to modification by prior treatment with substrate, by aging in the presence of chloramphenicol, and by treatment with dinitrophenol. Permeation and turbidity change are discussed in terms of a proposed phosphorylative mechanism of glucose transport.