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1.
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A reasonable degree of synchrony in the sporulation of Clostridium thermosaccharolyticum 3814 was obtained by using three 10% transfers of 8-hr cultures in a medium containing 0.5% L-arabinose, 0.5% peptone, 0.5% yeast extract, and Gc minerals. Sporulation was stimulated by L-arabinose and L-xylose, but was repressed by glucose, mannose, fructose, and D-pentoses. Sporulating cells were long and thin, whereas repressed cells were shorter and thicker. The optimal pH for sporulation was in the range of pH 5.0 to 5.5. As sporulation continued, the accumulated acetate decreased. Label studies indicated that a significant amount of acetate-2-C14 was incorporated into the spore lipid. The calcium, phosphorus, and dipicolinic acid (DPA) concentrations on a dry weight basis were 2.55, 2.60, and 7.25%, respectively. The molar ratio of Ca-DPA was 1.47.  相似文献   

3.
A reasonable degree of synchrony in the sporulation of Clostridium thermosaccharolyticum 3814 was obtained by using three 10% transfers of 8-hr cultures in a medium containing 0.5% L-arabinose, 0.5% peptone, 0.5% yeast extract, and Gc minerals. Sporulation was stimulated by L-arabinose and L-xylose, but was repressed by glucose, mannose, fructose, and D-pentoses. Sporulating cells were long and thin, whereas repressed cells were shorter and thicker. The optimal pH for sporulation was in the range of pH 5.0 to 5.5. As sporulation continued, the accumulated acetate decreased. Label studies indicated that a significant amount of acetate-2-C14 was incorporated into the spore lipid. The calcium, phosphorus, and dipicolinic acid (DPA) concentrations on a dry weight basis were 2.55, 2.60, and 7.25%, respectively. The molar ratio of Ca-DPA was 1.47.  相似文献   

4.
Summary Cellular impermeability associated with sporulating cells of Saccharomyces cerevisiae is caused by a rapid increase in the medium pH. Three factors have been identified as being important in regulating the rise in medium pH: 1) the cell density, 2) the potassium acetate concentration of the sporulation medium, and 3) and initial pH below 6.0. Sporulation conditions were established for strain 4579 which resulted in optimum uptake of 3H-adenine at T7, a period when the cells would be normally impermeable. Pulse-labeled polysomal RNA was characterized at T4 in naturally permeable cells of strain SK-1 and impermeable cells which required manipulation of the medium pH to facilitate uptake. Transfer ribonucleic acid (RNA), poly A-containing RNA and ribosomal RNA were synthesized in both cultures during the 20 min pulse. Furthermore, the rate of ribosomal RNA synthesis and processing into functional ribosomes approached the rate reported for vegetative cells. Initial sporulation conditions which caused a prolonged delay in the rise in medium pH adversely affected the kinetics of appearance and number of ascospores. The affect was shown to be on meiotic events since a reduction of sporulation was always accompanied by a reduction in the amount of intragenic recombination.  相似文献   

5.
The biological and biochemical studies of the effect of tenuazonic acid on plant cells and seedlings were carried out. Tenuazonic acid exhibited a conspicuous stunting effect on the seedling-growth of rice plant, mung bean, radish and turnip, and on the growth of suspension cultured cells of soybean and rice plants. Tenuazonic acid exhibited no effect on the O2-uptake and the activity of SH-enzyme of the plant, but inhibited the incorporation of 14C-Ieucine into the protein fraction and that of 14C-adenine into nucleic acid fraction of suspension cultured soybean cells as well as these uptake into the cells. And then it has been proved that these incorporation-inhibitions were not merely due to the inhibition of 14C-leucine and 14C-adenine uptake into the cells but based on the intrinsic inhibition of protein and nucleic acid syntheses, respectively.  相似文献   

6.
''Amsoy'' soybeans were grown for 2 months in nonsterilized Jackson silt loam amended to pH 4.0, 6.0, and 8.0. Nematodes were extracted biweekly from soil and roots. The greatest numbers of Pratylenchus alleni colonized soybean roots at pH 6.0. Hoplolaimus galeatus and members of the Tylenchinae-Psilenchinae survived best at pH 6.0, while numbers o f the Dorylaimoidea were greatest at both pH 6.0 and 8.0. The non-stylet nematodes were recovered in greater numbers from pH 8.0 soil. Potassium, manganese, and phenols were highest in soybean plants grown in pH 4.0 soil, the pH at which there were the fewest nematodes. A thicker suberized outer layer o f root tissue occurred in plants grown at pH 4.0.  相似文献   

7.
2,3-Dinitrilo-1,4-dithia-9,10-anthraquinone (DDA) is an effective inhibitor of respiration of intact cells ofMycobacterium smegmatis in the presence of glucose, glycerol, pyruvate, acetate and other citric acid cycle intermediates or substrates associate d with this cycle (glutamate, asparagine). DDA inhibits the incorporation of both14C-leucine and14C-adenine into appropriate macromolecules ofM. smegmatis (TCA-precipitable fractions), and causes a drop in the incorporated activity ofU-14C-glycine or its degradation products in all the cell fractions studied (lipids, RNA, DNA, proteins). DDA suppresses the growth ofM. smegmatis probably through an interference with the cell energy-carbon metabolism.  相似文献   

8.
Incorporation of 14C-phenylalanine, 14C-carbon dioxide, 14C-glucose,and 14C-glycine into the protein of Chlorella is inhibited bycycloheximide. A concentration of 2.5 µg per ml inhibitsincorporation by about 80 per cent; increasing the concentrationup to 10 µg per ml does not increase the degree of inhibition.The incorporation of 14C-adenine into ribonucleic acid (RNA)and deoxyribonucleic acid (DNA), and of 14C-glucose into polysaccharideis also inhibited. Unlike inhibition of protein synthesis, thatof nucleic acid and polysaccharide synthesis is observed onlyafter some delay. The delay is shortest for DNA synthesis andlongest for polysaccharide synthesis. Inhibition of 14C-glycineincorporation into DNA and RNA follows a similar pattern tothat obtained with 14C-adenine but the delay is much shorter.Cycloheximide also inhibits the formation of isocitrate lyasc(isocitrate-glyoxylate lyase, EC 4.1.3.1 [EC] ) when autotrophicallygrown cells are supplied with acetate.  相似文献   

9.
Rifampicin was found to inhibit the growth and incorporation of14C-adenine,14C-leucine and14C-glycine in exponentially growing cells ofM. smegmatis cultivated in Merrill’s synthetic medium. Increasing concentrations of the antibiotic inhibited respiration in resting cells, in the presence of glucose or 2-oxoglutarate as substrates in particular. In addition to the well-known interference of rifampicin with the biosynthesis of RNA, the effect on the energy metabolism should also be considered.  相似文献   

10.
Cultures of mitotic Chinese hamster cells, prepared by mechanical selection, were pulse-labeled with methionine-methyl-14C or with uridine-3H at different stages in the life cycle. The rate of 14C incorporation into 18S RNA was measured, as was the rate of uridine-3H incorporation into total RNA for both monolayer and suspension cultures. The rate of incorporation increased continuously throughout interphase in a fashion inconsistent with a gene-dosage effect upon RNA synthesis.  相似文献   

11.
MANY normal mammalian cells in culture are sensitive to a growth-inhibitory effect of cellular interaction, evidenced by an almost complete arrest of macromolecular synthesis and cellular division at relatively low population densities (contact inhibition of growth)1. It has, however, been shown that the environmental pH is an important element in this phenomenon2. In the bicarbonate-buffered media ordinarily used for animal cell cultures, an initial alkalinization to pH 7.8–8.0 as a result of CO2 loss is followed by the metabolic acidification of the medium to pH 6.8–7.0, at a rate determined by the population density and the metabolic activity of the specific cell. If, by the use of appropriate non-volatile buffers3,4, cells are kept at or near the pH optimal for the specific strain (H. E., unpublished work), the early contact inhibition of growth does not develop and the cells achieve population densities as much as two to four times greater than those ordinarily observed2.  相似文献   

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Abstract— The amino acid and carbohydrate metabolism of confluent cultures of C-6 glioma cells has been investigated. It was observed that the presence of glutamine in the incubation fluid was essential to maintain high glutamine levels in the cells during a 2 h incubation. When cells were incubated in a cerebrospinal fluid-like medium glutamate, glutamine, aspartate and γ-aminobutyrate (GABA) levels were comparable to those occurring in whole forebrain of adult rat in vivo. Glucose uptake was high, approx 1 μmol/mg protein/2 h, 50% of which was accounted for by lactate production. Of the remaining glucose uptake a substantial proportion was unaccounted for by known oxygen-coupled citric acid cycle flux, or glycogen or amino acid synthesis. Interestingly, the cells released into the medium significant amounts of the neuroinhibitory amino acids, GABA and glycine, and rapidly cleared the medium of the neuroexcitatory amino acids glutamate and aspartate. Metabolism of [2-14C]glucose and [3H]acetate by the cells indicated rapid labelling of the glutamate and aspartate pools of the cells by glucose in 1 h, but the relative specific activities of glutamine and GABA were much lower. The metabolism of tracer concentrations of [3H]acetate to glutamate by the cells indicated greater dilution of this isotope compared to that of labelled glucose. However, the ratio of 3H to 14C radioactivity in glutamate and other amino acids was similar to that in the mixture of glucose and acetate added to the medium. Therefore, some active route of acetate metabolism which communicates metabolically with the route of glucose metabolism to glutamate appears to exist in the cells. Significant acetate activation and fatty acid turnover would explain the present results. Some of the amino acid labelling patterns observed in these studies are not consistent with these glial-like cells behaving as models for the small compartment of amino acid metabolism in brain. Enzyme measurements corroborated the metabolic studies. Glutamate decarboxylase activity was 3–10% of the level found in whole brain. GABA transaminase was also low compared to brain as was glutamine synthetase. Glutamate dehydrogenase was present at levels equal to or higher than those of whole brain.  相似文献   

14.
The sexually agglutinative yeast Hansenula wingei lives in association with bark beetles that inhabit coniferous trees. This yeast was induced to sporulate by malt extract, which contains a high percentage of maltose (50%) and a low percentage of nitrogen (0.5%). A solution of 1.5% maltose without any growth factors also induced ascosporogenesis in H. wingei. Thus, only a carbon source is required for sporulation as in Saccharomyces. However, potassium acetate did not induce sporulation in H. wingei as it does in S. cerevisiae. Instead, disaccharides (such as maltose, sucrose, or cellobiose) promote sporulation better than either monosaccharides (such as dextrose, fructose, or mannose) or respiratory substrates (such as ethanol or glycerol). The specificity of disaccharides in promoting sporulation in H. wingei may be considered an adaptation since these disaccharides are present in the natural environment of this yeast. In addition, the specificity of disaccharides may be related to the induction of the disaccharidase because cells precultured on dextrose sporulate well on maltose, but cells precultured on maltose sporulate poorly on maltose. When (NH4)2SO4 was added at a low concentration (3 mM) to synthetic sporulation medium (1.5% maltose solution), sporulation was abolished, whereas other salts and nitrogen sources inhibited to a lesser extent and vitamins and trace elements had no effect. Oxygen was required for sporulation, as expected for an obligate aerobe. Maximal sporulation was achieved in 2% malt extract broth at high cell density (109 cells per ml), pH 5, and 25°C. By using these optimal physiological conditions and hybrid strains selected from an extensive genetic breeding program, about 30% asci (10% tetrads) were obtained routinely. Thus, the genetics of cell recognition in this yeast can now be studied.  相似文献   

15.
Addition of l-[U-14C]glutamate to a suspension of mechanically isolated asparagus (Asparagus sprengeri Regel) mesophyll cells results in (a) alkalinization of the medium, (b) uptake of l-[U-14C]glutamate, and (c) efflux of [14C]4-aminobutyrate, a product of glutamate decarboxylation. All three phenomena were eliminated by treatment with 1 millimolar aminooxyacetate. In vitro glutamate decarboxylase (GAD) assays showed that (a) 2 millimolar aminooxyacetate eliminated enzyme activity, (b) activity was pyridoxal phosphate-dependent, and (c) activity exhibited a sharp pH optimum at 6.0 that decreased to 20% of optimal activity at pH 5.0 and 7.0. Addition of 1.5 millimolar sodium butyrate or sodium acetate to cell suspensions caused immediate alkalinization of the medium followed by a resumption of acidification of the medium at a rate approximately double the initial rate. The data indicate that (a) continued H+/l-glutamate contransport is dependent upon GAD activity, (b) the pH-dependent properties of GAD are consistent with a role in a metabolic pH-stat, and (c) the regulation of intracellular pH during H+/l-Glu symport may involve both H+ consumption during 4-aminobutyrate production and ATP-driven H+ efflux.  相似文献   

16.
Natural isolates of two entomogenous fungi, Beauveria bassiana and Metarrhizium anisopliae, were cultured in liquid culture media containing 24 amino acids and KNO3 to determine their effect on growth and sporulation. In addition, the growth and medium pH changes for each isolate grown on an asparagine-containing medium were compared. Tryptophan and alanine were most effective for growth and sporulation of B. bassiana, although glutamine and KNO3 also produced large numbers of regularly shaped spores. Tryptophan, glutamic acid, and histidine were all well utilized for both growth and sporulation of M. anisopliae. Nitrogen sources containing sulfur were poorly utilized for sporulation by M. anisopliae. In general, B. bassiana produces greater mycelial mass and much larger numbers of spores than M. anisopliae. Both fungi attained nearly the same growth maximum on asparagine medium though B. bassiana exhibited an initially more rapid growth rate. In both fungi this rapid growth phase was accompanied by a decline in medium pH followed by a rise in pH during the decline phase of growth.  相似文献   

17.
Both chick embryo fibroblasts and mouse 3T3 cells reduce the rate at which they incorporate H3 uridine into RNA as their growth becomes inhibited at high cell density. This reduction occurs as a function of the cell population density, and with chick embryo cells (in contrast to 3T3 cells) it is not accompanied by significant medium alterations. This indicates the importance of the cell population density in the control of cellular metabolism. The decline in H3 uridine incorporation is paralleled by a decline in the rate of uptake of the isotope into the acid-soluble pool, suggesting that decreased entry of H3 uridine into the cell, rather than a decreased rate of RNA synthesis, is responsible for the reduced rate of incorporation into RNA of density-inhibited cells. This suggestion was confirmed by finding that when the restriction on uridine uptake was overcome by increasing the concentration of uridine in the medium, the density-dependent inhibition of uridine incorporation was largely reversed. We conclude that, even though the rate of H3 uridine incorporation into RNA is reduced three- to five-fold in density-inhibited cells, the rate of synthesis of pulse-labeled RNA continues at 70 to 85% of the rapidly-growing rate.  相似文献   

18.
19.
Chromosome Replication in Sporulating Cells of Bacillus subtilis   总被引:4,自引:4,他引:0       下载免费PDF全文
A method of specifically labeling the chromosomal terminus of Bacillus subtilis is described. When sporulating cultures were pulse-labeled with [3H]thymidine and then treated with 6-(p-hydroxyphenylazo)uracil, a drug which inhibits deoxyribonucleic acid (DNA) synthesis rapidly and completely, the only labeled spores formed were those that had completed replication during the pulse period. DNA-mediated transformation was used to show that the DNA of spores formed in the presence of 6-(p-hydroxyphenylazo)uracil had the same ratio of origin to terminus markers as DNA from untreated spores. Furthermore, spores formed in the presence of 6-(p-hydroxyphenylazo)uracil had the same DNA content as untreated spores. These two observations indicated that spores formed in the presence of 6-(hydroxyphenylazo)uracil contained completed chromosomes. The rate of termination of chromosomes destined to be packaged into spores was determined by this method, using the Sterlini-Mandelstam replacement system and a single medium exhaustion system for inducing sporulation. With both systems the rate of termination reached a broad peak 2 h after the start of sporogenesis. This was measured from the time of resuspension by using the replacement system and from the point where exponential growth ceased in the exhaustion system. The amount of spore DNA synthesized in the Sterlini-Mandelstam sporulation-inducing medium was very close to one-half the amount of the DNA present in mature spores. This suggests that chromosomes destined to be packaged into spores were replicated from close to the origin and possibly initiated in the sporulation-inducing medium. A method was devised for estimating the time taken to complete replication of the chromosomes destined to be packaged into spores. This was probably no more than 50 min. Whereas starvation must have occurred almost simultaneously in most cells in the population, the chromosome replication that was essential for sporogenesis was distributed over a wide time span. Thus, in some cells, replication started within 10 min of the nutritional step-down, but the peak rate was not reached for 1 h; thereafter replication continued at a substantial rate.  相似文献   

20.
To determine when the dormant mRNA of Blastocladiella emersonii zoospores is synthesized, the metabolism of poly(A) RNA and rRNA was studied during growth and sporulation using pulse-chase techniques. Zoospore poly(A) RNA is synthesized at all stages of the growth cycle investigated in cultures grown either on a normal 15-hr growth cycle or in minicyclic cultures induced to sporulate after only 6.5 hr growth. For cells labeled during the growth phase the specific activity of the pulse-labeled poly(A) RNA and rRNA was identical at the beginning and end of sporulation for any of the 2-hr labeling times investigated. From this it was concluded there is neither a preferential conservation nor degradation during sporulation of the poly(A) RNA and rRNA synthesized at various times during growth. Poly(A) RNA synthesized during early sporulation is preferentially degraded; in contrast, poly(A) RNA synthesized during late sporulation is conserved in the zoospore. Approximately one-third of the total zoospore poly(A) RNA accumulates during the final 15–20 min of sporulation. The accumulation rate for both poly(A) RNA and rRNA decreases as sporulation proceeds. In addition, the rate of degradation for both types of RNA decreases at later stages of sporulation.  相似文献   

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