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1.
D E Bradley 《Plasmid》1978,1(3):376-387
The IncX bacterial drug resistance plasmid R485 was found by electron microscopy to determine numerous very thin filaments (designated 485 pili) only 5.0 nm thick. They exhibited a characteristic helical structure (pitch, 4.6 nm), and were able to form large pseudocrystals when detached from the cell. The concomitant transfer of both pili and the sulfonamide resistance determinant of R485 to RecA strains of Escherichia coli confirmed that the pilus determinant was part of the plasmid and had not been mobilized from the chromosome of the host strain. An extensive examination failed to reveal any similar pili on strains carrying the IncX type plasmid R6K. 相似文献
2.
Adsorption of bacteriophages specific for Pseudomonas aeruginosa R factors RP1 and R1822 总被引:12,自引:0,他引:12
D E Bradley 《Biochemical and biophysical research communications》1974,57(3):893-900
Short, thick pili were found by electron microscopy on bacteria carrying the P group drug resistance plasmids RP1 and R1822. The R1822-specific phage PRR1 was seen to adsorb to the bases of the pili. Three RP1-specific phages, one filamentous (Pf3), and two with very thick capsids (PR3, PR4), were seen to attach all around the surface of cells, and were thought to be somatic, since pilus phages appear to be strictly polar on this species. PR3 and PR4 also lysed a strain of containing an N group plasmid, suggesting a relationship between the N and P group plasmids. 相似文献
3.
Doris Ursic John D. Kemp John P. Helgeson 《Biochemical and biophysical research communications》1981,101(3):1031-1037
Growth rates of two lines of tobacco () cell suspension cultures were measured in the presence or absence of G418, a new 2-deoxystreptamine antibiotic related to Gentamycin. Cell growth rates of . cv. Burley were inhibited at drug concentrations as low as 1.65 × 10?7 M. At 4 × 10?7 M, the doubling time was increased from 1.5 days (control) to 2.3 days (treatment). The drug was lethal to cells at 4 × 10?6 M, and inhibition was irreversible. Cells of . cv. Wisconsin 38 also were inhibited by the drug, although at slightly higher concentrations (ca. 2–5 fold).In view of our findings, G418 and its associated resistance factors could be of great value in plant genetic engineering. 相似文献
4.
A derivative of Escherichia coli K-12 (strain ) has been developed in which mutations in several genes can be detected simultaneously by plating parts of the bacterial population on different selective media. The mutation types include reversions from differently induced auxotrophies (nad-, arg-) aand (forward) mutations leading to resistance against 5-methytryptophan and to gal+ phenotype. It is assumed that many types of DNA alteration, including deletions and changes involving gross DNA regions, will lead to viable detectable mutants.The usefulness of strain E. coli was tested in spot tests, in liquid tests, in tests with extracts of mammalian organs, and in mammalian-mediated tests. It is concluded that strain is at least as useful in routine mutagenicity testing (especially in mammalian-mediated assays) as other present bacterial strains. 相似文献
5.
Temperature and light interact to modify the chemical and biochemical composition of a nitrogen-limited marine diatom, Thalassiosira allenii Takano, grown at a constant dilution rate in continuous culture and under a light:dark cycle.The percent of the total 14C incorporated into protein, polysaccharide and lipid, the N/C ratio and the C/cell varied with temperature in a markedly non-linear manner. The N/cell was negatively correlated to temperature. The Chl ratio was positively correlated with temperature under saturating light and non-saturating light for temperatures > 25 °C, but was constant under non-saturating light conditions for temperatures < 25 °C.Productivity index (PI) was negatively correlated to temperature under saturating light conditions, but did not vary under low light. In each case, the variation in PI with temperature was governed by the variation in Chl .The dark carbon loss rate was exponentially related to temperature and independent of light. Variation in the percent of the total 14C incorporated into protein and polysaccharide, the ratio and C/cell was primarily due to the effects of N-limitation < 20 °C and primarily due to the effects of temperature > 20 °C. Variation in N/cell was primarily due to the effects of temperature over the entire range of temperature studied. Variation in Chl was caused by the interaction of temperature and light effects.In most cases, temperature and nutrient effects interacted to govern how a particular parameter varied with temperature while light affected the range of values over which the parameter varied.The percent of the total 14C incorporated into protein exhibited a significant linear relationship with .The dark carbon loss rate, ratio and Chl ratio data were used to test the applicability of a model for the physiological adaptation of unicellular algae. The model, with parameters derived from a non-linear least-squares fit of the dark carbon loss rate data, adequately described the ratio between 15 and 25 °C at 290 and 137 μE · m?2 · s?1, but failed to describe the data at 28 °C and at 48 μE · m?2 · s?1. The Chl ratio was adequately described by the model under all light and temperature conditions. 相似文献
6.
J.Brice Weinberg Paul F. Smith Itzhak Kahane 《Biochemical and biophysical research communications》1980,97(2):493-499
The ability of various bacterial lipopolysaccharides and mycoplasmal lipopolysaccharides (lipoglycans) to induce macrophage-mediated tumor cell killing and amebocyte lysate clotting was determined. Lipoglycans from the mycoplasma or had no activity or 104 to 105 less activity than lipopolysaccharides from 0128:B12, K235, or R595 in causing lysate clotting and tumor cell killing by peritoneal macrophages from normal or bacillus Calmette-Guérin-infected mice. Previous studies have shown that the lipid A portion of bacterial lipopolysaccharide is responsible for the effects on macrophage-mediated tumor cell killing and lysate clotting. The known differences in the lipid structures of bacterial lipopolysaccharides and mycoplasmal lipopolysaccharides (lipoglycans) may account for the noted differences in the biologic potencies observed here. 相似文献
7.
Mefloquine, a quinoline-4-methanol antimalarial drug, also possesses bactericidal activity. Mefloquine causes rapid loss of bacterial viability, cell and spheroplast lysis, cessation of macromolecular synthesis, release of macromolecular constituents, and inhibition of the oxidation of NADH by isolated membranes. Results are consistent with the hypothesis that mefloquine is a membrane-active drug. 相似文献
8.
Diffusion of tetracycline across the outer membrane of Escherichia coli K-12: involvement of protein Ia. 总被引:4,自引:0,他引:4
The possibility that passage of tetracycline across the outer membrane of K-12 is controlled by one or more of the proteins Ia, Ib and II1 (Henning's nomenclature) was investigated. A mutant lacking protein Ia (obtained by selection for resistance to phage TuIa) was more resistant to tetracycline than wild-type strains or those lacking only proteins Ib or II1. The envelope protein composition of a tetracycline-resistant mutant () was altered in several respects, but the major change involved loss of protein Ia. These data support our previous suggestion [12] that tetracycline diffuses across the outer membrane through hydrophilic regions. Furthermore, they imply that only protein Ia plays a significant role in the passage of this antibiotic across the outer membrane. 相似文献
9.
Washed human erythrocytes were cooled at different rates from +37 °C to 0 °C in hypertonic solutions of either NaCl (1.2 m) or of a mixture of sucrose (40% ) with NaCl (2.53% ). Thermal shock hemolysis was measured and the surviving cells were examined for their mass and cell water content and also for net movements of sodium, potassium, and 14C-sucrose. The results were compared with those obtained from cells in sucrose (40% ) initially, cooled at different rates to ?196 °C and rapidly thawed.The cells cooled to 0 °C in NaCl (1.2 m) showed maximal hemolysis at the fastest cooling rate studied (39 °C/min). In addition in the surviving cells this cooling rate induced the greatest uptake of 14C-sucrose and increase in cell water and cell mass and also entry of sodium and loss of cell potassium. A different dependence on cooling rate was seen with the cells cooled from +37 °C to 0 °C in sucrose (40% ) with NaCl (2.53% ). In this solution, survival decreased both at slow and fast cooling rates correlating with the greatest uptake of cell sucrose and increase in cell water. There was extensive loss of cell potassium and uptake of sodium at all cooling rates, the cation concentrations across the cell membrane approaching unity.The cells frozen to ?196 °C at different cooling rates in sucrose (40% ) initially, also showed sucrose and water entry on thawing together with a loss of cell potassium and an uptake of cell sodium. More sucrose entered the cells cooled slowly (1.8 ° C/min) than those cooled rapidly (318 ° C/min).These results show that cooling to 0 °C in hypertonic solutions (thermal shock) and freezing to ?196 °C both induce membrane leaks to sucrose as well as to sodium and potassium. These leaks are not induced by the hypertonic solutions themselves but are due to the effects of the added stress of the temperature reduction on the membranes modified by the hypertonic solutions. The effects of cooling rate are explicable in terms of the different times of exposure to the hypertonic solutions. These results indicate that the damage observed after thermal shock or slow freezing is of a similar nature. 相似文献
10.
The respiratory adaptation process in both wild-type and UV-sensitive strains of was sensitive to small doses of UV-radiation (10 and 0.7 J/m2, respectively). These doses of irradiation were ineffective in arresting induced synthesis of acid phosphatase and catalase. Exposure of the irradiated cells to visible light (370 – 800 nm) could completely restitute the impaired respiratory adaptation process. UV irradiation at these doses affected DNA and RNA synthesis in maturing mitochondria in both the yeast strains. The UV-induced block could however be eliminated by exposure of the cells to visible light. These results suggest that the lesion in the UV-induced block in the respiratory adaptation may be in the DNA of promitochondria. 相似文献
11.
Immediate fragmentation of parental DNA by near-ultraviolet irradiation at 313 nm was measured in cultured skin fibroblasts from normal individuals, patients with Xeroderma pigmentosum of complementation group A (XPA) and Xeroderma pigmentosum variants (XPV) by the alkaline elution procedure. For a dose of 2.25 KJm?2 given at Oo fragmentation was comparable in all cell strains. However, fragmentation was strongly increased relative to Oo in XPV but not in normal fibroblasts and the XPA strains when irradiation was carried out at 37o. From our results it appears that a step in the repair of DNA is abnormal in XPV. 相似文献
12.
Membrane mutation related to the production of extracellular -amylase and protease in bacillus subtilis 总被引:13,自引:0,他引:13
Mutants which had a genetic character to increase the production of both α-amylase and protease simultaneously, were isolated from a transformable strain of Marburg by NTG treatment. This mutation seems to have occurred at a single gene of the bacterial chromosome and was not linked to 116 which was closely linked to the α-amylase gene. When this mutation and an α-amylase regulator gene (h) coexisted in one strain, their synergistic effect on extracellular α-amylase production ws observed. The introduction of this mutation resulted in a loss of competence for the transformation. The SDS disc gel electrophoretic profiles of the membrane proteins from the original strain, the mutants and transformants with this mutation showed a remarkable difference in one component. 相似文献
13.
Klaus Gietzen Peter Adamczyk-Engelmann Andreas Wüthrich Anka Konstantinova Hermann Bader 《生物化学与生物物理学报:生物膜》1983,736(1):109-118
Compound , a condensation product of N-methyl-p-methoxyphenethylamine with formaldehyde, is composed of a family of cationic amphiphiles differing in the degree of polymerization. Compound was found to be a potent inhibitor of the calmodulin-activated fraction of brain phosphodiesterase and red blood cell Ca2+-transport ATPase, with IC50 values of 0.3 and 0.85 μg/ml, respectively. However, the basal activity of both enzymes is not at all suppressed by the drug at concentrations up to 300 μg/ml. Inhibition of Ca2+ transport into inside-out red blood cell vesicles by compound follows a similar pattern in that basal, calmodulin-independent, transport is also not affected by the drug. Kinetic analysis revealed that the stimulation of Ca2+-transport ATPase induced by calmodulin is inhibited by compound according to a competitive mechanism. It was demonstrated that the inhibitory constituents of compound bind to calmodulin in a Ca2+-dependent fashion. Comparison of the specificity of several anti-calmodulin drugs showed that compound is the most specific inhibitor of the calmodulin-dependent fraction of red blood cell Ca2+-transport ATPase that has been described hitherto. In addition, compound was found to be a rather specific inhibitor of the calmodulin-induced activation of Ca2+-transport ATPase when compared with the stimulation induced by an anionic amphiphile or by limited proteolysis. Half-maximal inhibition of the activity stimulated by oleic acid or mild tryptic digestion required 8- and 32-times higher concentrations of compound , respectively, compared with the calmodulin-dependent fraction of the ATPase activity. Moreover, calmodulin-independent systems as rabbit skeletal muscle sarcoplasmic reticulum Ca2+-transport ATPase or calf cardiac sarcolemma (Na+ + K+)-transport ATPase are far less influenced by compound as compared with trifluoperazine and calmidazolium. Because of its high specificity compound is proposed to be a promising tool for studying calmodulin-dependent processes. 相似文献
14.
K S Sundaram T A Venkitasubramanian 《Biochemical and biophysical research communications》1977,78(2):839-845
The effect of various sub-inhibitory concentrations of isoniazid on tryptophan uptake by H37Rv grown and was studied. Uptake, measured after 3 minutes of drug exposure was inhibited mildly by 0.1 μg/ml and 0.2 μg/ml concentration and completely by 0.3 μg/ml. However, with the minimal inhibitory concentration (MIC)7 of 0.5 μg/ml, not only inhibition but also a strong efflux of the preformed tryptophan pool were observed. The results are discussed in the light of the theory that isoniazid interferes with the cell wall mycolate synthesis. 相似文献
15.
Transient inhibition by cycloheximide of protein synthesis in cultured plant cell suspensions: a dose response paradox 总被引:6,自引:0,他引:6
cell suspension cultures supplied with high concentrations (>10?5M) of cycloheximide (CH) rapidly develop a resistance to the drug under conditions in which protein synthesis is initially severely impaired. CH at 10?6M, while equally effective in inhibiting protein synthesis, is markedly less efficient in inducing resistance. Development of resistance is not due to selection, or to induction of the capacity to metabolize the drug. Cells washed free of CH retain their resistance over several generations before reverting to the CH-sensitive condition. 相似文献
16.
F F Campo M Hernández-Asensio J M Ramírez 《Biochemical and biophysical research communications》1975,63(4):1099-1105
The initial rate of uptake of methyl α-D-glucopyranoside by is inhibited by respiration. The inhibition is more pronounced in mutant strains which cannot use the energy-rich state of the membrane to form ATP because of a defective Ca2+, Mg2+-activated ATPase. In both mutant and normal strains, the inhibition of glucoside uptake is not accompanied by an increase of the ATP content of the cells and is abolished by carbonyl cyanide -chlorophenylhydrazone, a drug which dissipates membrane energy. It appears, therefore, that the inhibitory effect of respiration is mediated by the energy-rich state of the membrane and that ATP does not participate in the inhibition. 相似文献
17.
cultures of sp. were exposed to various concentrations of hydroxyurea (HU) during the logarithmic phase. In the presence of 5 × 10?2M HU, cell division was completely blocked after an initial increase in cell numbers by about 20%. Inhibition of incorporation of 3H-thymidine into acid-insoluble material was effective within 1 hr of exposure to the drug (5 × 10?2M) and it reached a level of 80% after 8 hr. At lower concentrations (5 × 10?4M ? 1 × 10?3M), however, incorporation of 3H-thymidine was remarkably increased while cell division remained unaffected indicating that the increase in incorporation was not due to increased DNA synthesis in preparation for cell division. 相似文献
18.
The antibody response to RGG of 8-wk old mice of various strains was assessed in terms of half-lives () of lightly iodinated rabbit gamma globulin (131I-RGG) elimination. was increased if the small aggregate content in 131I-RGG was reduced. The effect of aggregates was least in AKR, largest in Balb/c and SJL and intermediate in the majority of strains, typified by A mice. Differences between various strains, in the degree of tolerance to aggregate freed RGG (centrifuged at 123,000 g), were observed. The level of residual responsiveness was greatest in SJL mice. More profound tolerance could be induced with biofiltered RGG. Resistance of SJL mice to tolerance induction was also observed when human gamma globulin (HGG) and bovine serum albumin served as tolerogen. Tolerance to RGG and sheep red cells was induced in cyclophosphamide-treated SJL animals. 相似文献
19.
W H McClain 《Biochemical and biophysical research communications》1979,86(3):718-724
Synthesis of T4 tRNAGln depends on normal levels of ribonuclease III. Infection of cell strains carrying a mutation in the gene for this enzyme resulted in severe depression in tRNAGln production, as revealed by chemical and suppressor tRNA analyses. The remaining seven T4 tRNAs were synthesized in the mutant cells. The requirement of ribonuclease III for synthesis of tRNAGln points to an essential cleavage by the enzyme of a precursor RNA containing tRNAGln. 相似文献
20.
P.G. Wislocki A.W. Wood R.L. Chang W. Levin H. Yagi O. Hernandez D.M. Jerina A.H. Conney 《Biochemical and biophysical research communications》1976,68(3):1006-1012
(±)-7β,8α-Dihydroxy-9β,10β-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BP 7,8-diol-9,10-epoxide) is a suspected metabolite of benzo[a]pyrene that is highly mutagenic and toxic in several strains of and in cultured Chinese hamster V79 cells. BP 7,8-diol-9,10-epoxide was approximately 5, 10 and 40 times more mutagenic than benzo[a]pyrene 4,5-oxide (BP 4,5-oxide) in strains TA 98 and TA 100 of and in V79 cells, respectively. Both compounds were equally mutagenic to strain TA 1538 and non-mutagenic to strain TA 1535 of . The diol epoxide was toxic to the four bacterial strains at 0.5–2.0 nmole/plate, whereas BP 4,5-oxide was nontoxic at these concentrations. In V79 cells, the diol epoxide was about 60-fold more cytotoxic than BP 4,5-oxide. 相似文献