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1.
The DNA transformation in the industrial erythromycin-producing Saccharopolyspora erythraea was investigated as standard protoplast transformation methods are ineffective. Intergeneric conjugal transfer of DNA from E. coli demonstrated transformation efficiencies from 0.05 × 10−8 to 7.2 × 10−8 exconjugants generated per recipient. Electroporation-mediated methodologies were also established. More than 105 transformants were acquired per μg DNA. The proposed protocol provides an alternative route for the introduction of DNA into industrial strains.  相似文献   

2.
Changes in the hormone content of Tetrahymena pyriformis GL were investigated during histamine, serotonin or insulin treatment at concentrations of 10−6M to 10−21M for 30 min. The immunologically demonstrable hormone content was studied by using specific antibodies, flow cytometry and confocal microscopy. Histamine at the higher ranges elevated the serotonin content of Tetrahymena, whereas serotonin at the lower ranges (down to 10−21M) decreased its histamine levels. Insulin did not affect its serotonin content, whereas serotonin increased its insulin content at each concentration studied (down to 10−21M). Insulin between 10−6M and 10−21M increased the hista-mine levels of Tetrahymena, although histamine influenced its insulin level only at 10−6M. Our results call attention to the presence of hormonal interactions even at “low” levels of phylogeny and to the extreme sensitivity of the hormone receptors of Tetrahymena. These data might explain (1) the requirement of Tetrahymena for (vertebrate) hormone production and hormone receptors and (2) the way that it uses these hormones under natural conditions.This work was supported by the National Research Fund (OTKA-T-037303), Hungary.  相似文献   

3.
Chromosomal deoxyribonucleic acid was isolated and purified from 10 strains ofFlavobacterium breve, originating from human or other animal sources. The mean and standard deviation for the species in base content was 32.4±0.6% G+C, and in genome size was 3.21±0.37×109 daltons. In vitro DNA reassociation showed that sevenF. breve strains (mainly from human sources) had high levels of intraspecific base sequence similarity (>70%) as derived from reassociations done at the optimum temperature of reassociation (TOR) or TOR—10°C (nonstringent conditions). The three otherF. breve strains contained a high degree of base sequence divergence. All 10 strains ofF. breve were readily distinguishable in their DNA characteristics fromF. meningosepticum, F. odoratum, and allied Gram-negative bacteria.  相似文献   

4.
Tetrahymena in the log phase of growth were pulse labeled with uridine-3H, fixed in acetic-alcohol, extracted with DNase, and embedded in Epon. 0.5-µ sections were cut, coated with Kodak NTB-2 emulsion, and developed after suitable exposures. Grains were counted above macronuclei, above 1000 micronuclei, and above 1000 micronucleus-sized "blanks" which were situated next to micronuclei in the visual field by means of a camera lucida. An analysis of grain counts showed that micronuclei were less than ½000 as active as macronuclei on the basis of grains per nucleus. Since micronuclei contained, on the average, about ½0 as much DNA as macronuclei, micronuclear DNA had less than 1% of the specific activity of macronuclear DNA in RNA synthesis. However, even this small amount of apparent incorporation was not significantly different from zero. Comparisons of the frequency distributions of labeled micronuclei with those of micronuclear "blanks" showed no evidence of a small population of labeled nuclei such as might be expected if micronuclei synthesized RNA for only a brief portion of the cell cycle. We conclude from these studies that there is no detectable RNA synthesis in Tetrahymena micronuclei during vegetative growth and reproduction.  相似文献   

5.
The goal of this paper was to explain variability of phytoplankton in a shallow coastal area in relation to physico-chemical parameters. Temporal variability and composition of phytoplankton were investigated in the Kotor Bay, a small bay located in the south-eastern part of the Adriatic Sea. Samplings were performed weekly from February 2008 to January 2009 at one station in the inner part of the Kotor Bay, at five depths (0 m, 2 m, 5 m, 10 m, 15 m). Phosphates, nitrites and nitrates ranged from values under the level of detection to the maximum values of 1.54, 1.53 and 23.91 μmol l−1, respectively. The phytoplankton biomass — represented by chlorophyll a concentration — ranged from 0.12 to 6.78 mg m−3, reaching a maximum in summer. Diatoms were present throughout the whole sampling period, reaching the highest abundance in March (3.42×105 cells l−1at surface). The peak of dinoflagellates in July (2.2×106 cells l−1 at surface) was due to a single species, Prorocentrum micans. The toxic dinoflagellate Dinophysis fortii occurred at a concentration of 2140 cells l−1 in May. The present results of phytoplankton assemblages and distribution provide valuable information for this part of the south-eastern Adriatic Sea where data is currently absent.  相似文献   

6.
Specific activity of aquatic bacteria, which indicates average heterotrophic activity per bacterial cell, was determined asV max per bacterium and turnover rate per bacterium for glucose mineralization at different sites (river and estuary) in north Humberside, northeast England.V max per bacterium ranged from 0.05×10−13 to 52.2×10−13 mg/h and turnover rate per bacterium from 0.05×10−8 to 88.3×10−8 ml/h. Highest mean values were found at river sites and the lowest at an outer estuary site, although there was considerable variation at each site and ranges from all sites overlapped. Also, ranges ofV max per bacterium from Humberside sites in general overlapped published ranges for sites in other geographical areas.V max per bacterium and turnover rate per bacterium were significantly correlated with some environmental variables, which suggests that they are of ecological significance.  相似文献   

7.
Macronuclei of Tetrahymena pyriformis contain approximately 200 copies of the genes for 25S and 17S ribosomal RNA (rRNA) per haploid genome. Micronuclei, however, contain only a few copies of the rRNA genes per haploid complement. Since macronuclei develop from, products of meiosis, fertilization and division of micronuclei, we suggested that the multiple copies of the rRNA genes in macronuclei are generated by amplification of the small number of genes in micronuclei (Yao et al., 1974). This process provides a simple mechanism for maintaining the homogeneity of the repeated rRNA genes. To test if amplification is a general mechanism operating on all repeated genes in Tetrahymena, we have examined the numbers of 5S RNA and tRNA genes in macro- and micronuclei. 5S RNA was purified by polyacrylamide gel electrophoresis and hybridized to saturation against macro- and micronuclear DNA. Approximately 0.013–0.014% of macronuclear DNA and about 0.009% of micronuclear DNA is complementary to 5S RNA. After correcting for the differences in the DNA sequence complexities between the two nuclei, we calculate that there are 300–350 5S genes per haploid macro- or micronuclear genome. From these data we conclude that there is little or no detectable amplification of the 5S genes in macronuclei relative to micronuclei. Similar studies using tRNA indicate that these genes are also highly repeated in both nuclei; about 800 genes are present per haploid genome. Thus, amplification from a small number of genes can be excluded as the mechanism for generating the repeated copies of the 5S and tRNA genes in Tetrahymena and it is likely that another, as yet unidentified, mechanism operates to maintain the homogeneity of these genes.  相似文献   

8.
In this study, four real-time polymerase chain reaction (PCR) primer sets were developed for the 16S rRNA genes of specific ammonia-oxidizing bacteria (AOB) found in activated sludge of sewage treatment systems. The primer sets target two of several sequence types of the Nitrosomonas oligotropha cluster, members within the Nitrosomonas communis cluster, and all members of the Nitrosomonas europaeaNitrosococcus mobilis cluster. The detection limit of each primer set was in the range of 3×101–6×102 genes reaction−1. Reliable quantification of the target AOB DNA was obtained when the target AOB DNA comprised more than 0.1% of total AOB DNA in the sample. The application of the primer sets to samples taken from five sewage treatment systems showed that, in all systems, the majority of the AOB population was comprised of one sequence type of the N. oligotropha cluster (3.9±1.5×109–1.7±0.5×1010 cell l−1) and, in most systems, followed by members within the N. communis cluster (2.8±0.3×109–1.0±0.1×1010 cell l−1) or/and another sequence type of the N. oligotropha cluster (1.5±0.6×108–5.5±0.5×108 cell l−1). N. europaeaN. mobilis cluster arose solely in small numbers (4.9±0.8×108 cell l−1) in one system. Real-time PCR-amplified products obtained from genomic DNA extracted from samples were verified using clone library, and it revealed that only the target AOB DNA were PCR amplified, without amplification of the nontarget sequences.  相似文献   

9.
The harmful effects of surfactants to the environment are well known. We were interested in investigating their potential toxicity in a pure culture of Acinetobacter junii, a phosphate (P)-accumulating bacterium. Results showed a high acute toxicity of sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HDTMA) against A. junii. The estimated EC50 values of the HDTMA for the inhibition of CFUs in the pure culture of A. junii was 3.27 ± 1.12 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 2.47 ± 0.51 × 10−6 mol L−1. For SDS, estimated EC50 values for the inhibition of CFUs in the pure culture of A. junii was 5.00 ± 2.95 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 3.33 ± 0.96 × 10−4 mol L−1. The obtained EC50 values in the standardised yeast toxicity test using Saccharomyces cerevisiae were 3.03 ± 0.38 × 10−4 and 4.33 ± 0.32 × 10−5 mol L−1 for SDS and HDTMA, respectively. These results emphasized the need to control concentrations of surfactants entering the activated sludge system. The negative effects of these toxicants could greatly decrease populations of P-accumulating bacteria, as well as eukaryotic organisms, inhabiting activated sludge systems, which in turn could result in the decrease of the system efficiency.  相似文献   

10.
Macro- and micronuclei were isolated from Tetrahymena pyriformis (Syngen 1, strain WH-6) and their DNAs compared by isopycnic centrifugation in neutral and alkaline CsCl, by analysis of thermal denaturation properties and by molecular hybridization. Unlike the situation observed in Stylonychia the buoyant densities and thermal denaturation patterns of Tetrahymena macro- and micronuclear DNAs were virtually identical—the only observable differences bordering on the limits of resolution of these techniques. DNA was isolated from the two nuclei which had been labelled with different radioactive isotopes (i.e. 14C-thymidine and 3H-thymidine), and the renaturation kinetics of mixtures of macro- and micronuclear DNA were examined using a single-strand specific deoxyribonuclease (S1). Renaturation kinetics obtained using varying ratios of macro- and micronuclear DNA suggested that 80–90% of the sequences present in micronuclei were present in similar amounts in macronuclei. However, careful analyses of the renaturation kinetics indicate that approximately 10–20% of the sequences found in micronuclei are probably absent in macronuclei, and that most of these sequences are probably moderately repetitive (100 copies per genome or less). These findings place severe constraint on possible models concerning the structure of the Tetrahymena macronucleus, and are very different from the situation observed in Stylonychia where it has been suggested that only a small percentage of the sequences in micronuclei are present in significant amounts in macronuclei. Nonetheless, these results along with those in Stylonychia can be taken as an indication that the loss or under-replication of some DNA sequences accompanies macronuclear differentiation in ciliates.  相似文献   

11.
DNA of ciliated protozoa   总被引:1,自引:1,他引:0  
DNA was isolated from macronuclei and micronuclei of the ciliated protozoan, Stylonychia mytilus under conditions that minimize the possibility of DNA degradation. Macronuclear DNA has an S value of 10 to 11 in sucrose gradients. Macronuclear DNA has an average molecular weight of 1.15×106 daltons and a range of molecular weights of 1.0×106 to 1.95×106 daltons. The average length of macronuclear DNA, measured by electron microscopy, is 0.80 microns and the range is 0.2 to 2.2 microns. Almost all micronuclear DNA pieces are too long to be measured by electron microscopy. The shortest piece of micronuclear DNA found was 15.0 microns in length.  相似文献   

12.
The antibacterial effect of cationic surfactants against the pure culture of phosphate (P)-accumulating bacterium Acinetobacter junii was investigated. The estimated EC50 values of the N-dodecylpyridinium chloride (DPC) for growth inhibition was 1.4±0.5 × 10−6 mol L−1 and for the inhibition of the P-uptake rates 7.3±2.6 × 10−5 mol L−1. The estimated EC50 values of the N-cetylpyridinium chloride (CPC) for growth inhibition was 4.9±1.3 × 10−7 mol L−1 and for the inhibition of the P-uptake rates 7.7±2.9 × 10−6 mol L−1. This suggests the importance of controlling the amounts of cationic surfactants in influent of the wastewater treatment systems in order to avoid the possible failure of the biological P removal from wastewaters.  相似文献   

13.
Culturable counts of antibiotic resistant, genetically engineeredPseudomonas fluorescens were determined on antibiotic-containing plate count agar during starvation in water. Prior to starvation, colony counts obtained on all media separated into two groups. The mean of the colony counts on plate count agar with or without tetracycline (4.9 × 106 ml−1) was significantly higher than the mean colony counts on plate count agar containing either nalidixic acid or nalidixic acid plus tetraclycline (2.5×106 ml−1). After 20 days of starvation the highest mean colony counts continued to be obtained on plate count agar (7.2 × 106 ml−1) with slightly, but significantly, lower counts obtained on plate count agar containing either nalidixic acid (5.6 × 106 ml−1) or tetraclycline (1.5×106 ml−1). A combination of nalidixic acid and tetracycline in plate count agar, however, dramatically reduced colony counts (8.3 × 102 ml−1) after this starvation period. The addition of catalase to plate count agar containing nalidixic acid and tetracycline negated the effect caused by this combination of antibiotics. When colony counts obtained over the entire 20 day incubation were considered, the addition of MgSO4 to plate count agar containing nalidixic acid and tetracycline resulted in a significant increase in colony counts. Other combinations of antibiotics, nalidixic acid+carbenicillin, nalidixic acid+kanamycin, streptomycin+tetracycline, streptomycin+carbenicillin, rifampicin+tetracycline, rifampicin+carbenicillin, and rifampicin+kanamycin, did not inhibit colony formation of starved cells. Antibiotic resistant strains ofP. putida andEscherichia coli also displayed sensitivity to the combination of nalidixic acid and tetracycline in plate count agar after starvation.  相似文献   

14.
Summary The ability of Pseudomonas aeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pK i =1.66±3.26×10−3, 1.92±1.63×10−4 and 2.16±3.79×10−4) and binding constant of cadmium metal ions (pK M1=1.99±2.45×10−3 and pK M2=1.67±4.08×10−3) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pK f) constant is 2.04±2.1×10−5 suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (q max) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10−3± 2.10×10−3, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains.  相似文献   

15.
Summary An essential component of anyin vitro model for endothelial permeability is a confluent cell monolayer. The model reported here utilizes primary human umbilical vein endothelial cells (HUVEC) cultured on recently developed polyethylene terephthalate micropore membranes. Using a modification of the Wright-Giemsa stain, confluent HUVEC monolayers grown on micropore membranes were routinely assessed using light microscopy. Determination of confluence using this method was confirmed by scanning electron microscopy. Transendothelial electrical resistance of HUVEC monolayers averaged 27.9±11.4 Ω · cm2, 10 to 21% higher than literature values. Studies characterizing the permeability of the endothelial cell monolayer to3H-inulin demonstrated a linear relationship between the luminal concentration of3H-inulin and its flux across HUVEC monolayers. The slope of the flux versus concentration plot, which represents endothelial clearance of3H-inulin, was 2.01±0.076 × 10−4 ml/min (r2=.9957). The permeability coefficient for the HUVEC monolayer-micropore membrane barrier was 3.17±0.427×10−6 cm/s with a calculated permeability coefficient of the HUVEC monolayer alone of 4.07±0.617×10−6 cm/s. The HUVEC monolayer reduced the permeability of the micropore membrane alone to3H-inulin (1.43±0.445×10−5 cm/s) by 78%. Evans blue dye-labeled bovine serum albumin could not be detected on the abluminal side without disruption of the HUVEC monolayer. These results demonstrate a model for endothelial permeability that can be extensively assessed for monolayer integrity by direct visualization, transendothelial electrical resistance, and the permeability of indicator macromolecules.  相似文献   

16.
The bacteriostatic potency of the cerium-humic acid complex was evaluated by experimental measurement of this complex interaction with E. coli, Bacillus pyocyaneus, Staphylococcus aureus, Leuconostoc and Streptococcus faecalis, and by comparison bacteriostatic effects with the cerium-citrate complex. The experimental results indicated that the cerium-humic acid complex strongly inhibited growth of all five bacterial strains, and its diameter of bacteriostatic circles were more than 30 mm. The minimal bacteria-inhibiting concentration were 1×10−3, 2×10−3 and 1×10−2 mol/L for E. coli and Bacillus pyocyaneus, Staphylococcus aureus, and Leuconostoc and Streptococcus faecalis individually, and the measured minimal bactericidal concentrations were 2×10−3 and 1×10−2 mol/L for Bacillus pyocyaneus, E. coli, and Leuconostoc. To kill Staphylococcus aureus and Streptococcus faecalis, the concentration had to be more than 1×10−2 mol/L. On the contrary, we found that cerium-citrate complex did not inhibit the growth of the above five bacteria, but stimulated bacterial growth. The completely different bacteriostatic results of two cerium complexes may hint that the association and chemical properties of the two complexes were different.  相似文献   

17.
Bdellovibrio spp. strains 6-5-S, 100, 109 (Davis), and A3.12 multiply in the presence of viable but non-proliferating or heat-killed (70 or 100 C, 10 min; 121 C, 5 min) cells ofSpirillum serpens strain VHL suspended in buffers supplemented with Ca++ and/or Mg++. Ca++ (optimal, 2 × 10−3 m) and Mg++ (optimal, 2 × 10−5 m) independently stimulate the groth of bdellovibrios: additive effects are noted. Multiplication ofBdellovibrio in the presence of Ca++ and Mg++ is associated with the release into the culture supernatant solution of UV-absorbing materials and of amino sugars (presumably by activating or stabilizing lytic enzymes). The growth rate ofBdellovibrio strain 6-5-S in suspensions of heat-killed host cells is lower than in living but non-proliferating host cells. Bdellovibrio spp. strains 100, 109 (Davis), 109 (Jerusalem), A3.12, and 6-5-S all require added Ca++ for growth in cell suspensions of homologous or heterologous host bacteria which have been grown in minimal medium.Bdellovibrio sp. strain 109 (Jerusalem) is capable of growing in the presence of the low level of Ca++ boundin situ to the cells of its host,E. coli B, when the host cells had been cultivated in a complex medium but not when the host cells had been grown in a Ca++-depleted minimal medium (except when Ca++ is added). Addition of ethylenediaminetetraacetic acid (0.01m) preventsBdellovibrio growth, which is restored by addition of Ca++ and Mg++. The nonparasitic growth ofBdellovibrio spp. strains 100, 109, A3.12, and 6-5-S in heat-killed cell suspensions only in the presence of added cations indicates that, in this system, the cations are essential for activity of bacteriolytic and other enzymes and that they might also directly affectBdellovibrio growth rather than — as may be the case in other systems of live host cells plusBdellovibrio — only indirectly by affecting attachment to the host cell, maintaining integrity of the host spheroplasts, and increasing the burst size.  相似文献   

18.
In this report we are examining how the antioxidant flavonoids can prevent DNA damage and what mechanism of action is involved in the process. Flavonoids are strong antioxidants that prevent DNA damage. The anticancer and antiviral activities of these natural products are implicated in their mechanism of actions. We study the interactions of quercetin (que), kaempferol (kae), and delphinidin (del) with DNA and transfer RNA in aqueous solution at physiological conditions, using constant DNA or RNA concentration 6.25 mmol (phosphate) and various pigment/polynucleotide(phosphate) ratios of 1/65 to 1 (DNA) and 1/48 to 1/8 (tRNA). The structural analysis showed quercetin, kaempferol, and delphinidin intercalate DNA and RNA duplexes with minor external binding to the major or minor groove and the backbone phosphate group with overall binding constants for DNA adducts K que = 7.25 (±0.65) × 104 M−1, K kae = 3.60 (±0.33) × 104 M−1, and K del = 1.66 (±0.25) × 104 M−1 and for tRNA adducts K que = 4.80 (±0.50) × 104 M−1, K kae = 4.65 (±0.45) × 104 M−1, and K del = 9.47 (±0.70) × 104 M−1. The stability of adduct formation is in the order of del>que>kae for tRNA and que>kae>del for DNA. Low flavonoid concentration induces helical stabilization, whereas high pigment content causes helix opening. A partial B to A-DNA transition occurs at high drug concentration, while tRNA remains in A-family structure. The antioxidant activity of flavonoids changes in order delphinidin>quercetin>kaempferol. The results show intercalated flavonoids can make them strong antioxidants to protect DNA from harmful free radical reactions.  相似文献   

19.
Databases on effects of chronic low-LET radiation exposure were analyzed by non-parametric statistical methods, to estimate the threshold dose rates above which radiation effects can be expected in vertebrate organisms. Data were grouped under three umbrella endpoints: effects on morbidity, reproduction, and life shortening. The data sets were compiled on a simple ‘yes’ or ‘no’ basis. Each data set included dose rates at which effects were reported without further details about the size or peculiarity of the effects. In total, the data sets include 84 values for endpoint “morbidity”, 77 values for reproduction, and 41 values for life shortening. The dose rates in each set were ranked from low to higher values. The threshold TDR5 for radiation effects of a given umbrella type was estimated as a dose rate below which only a small percentage (5%) of data reported statistically significant radiation effects. The statistical treatment of the data sets was performed using non-parametric order statistics, and the bootstrap method. The resulting thresholds estimated by the order statistics are for morbidity effects 8.1 × 10−4 Gy day−1 (2.0 × 10−4–1.0 × 10−3), reproduction effects 6.0 × 10−4 Gy day−1 (4.0 × 10−4–1.5 × 10−3), and life shortening 3.0 × 10−3 Gy day−1 (1.0 × 10−3–6.0 × 10−3), respectively. The bootstrap method gave slightly lower values: 2.1 × 10−4 Gy day−1 (1.4 × 10−4–3.2 × 10−4) (morbidity), 4.1 × 10−4 Gy day−1 (3.0 × 10−4–5.7 × 10−4) (reproduction), and 1.1 × 10−3 Gy day−1 (7.9 × 10−4–1.3 × 10−3) (life shortening), respectively. The generic threshold dose rate (based on all umbrella types of effects) was estimated at 1.0 × 10−3 Gy day−1.  相似文献   

20.
By means of microcalorimetry, the effect of four copper(II) complexes on Tetrahymena growth was investigated. The extent and duration of the inhibitory effect on the metabolism, judged by the rate constant, k, and the half inhibition concentration, IC50, varied with the different complexes. The results showed that the half inhibition concentrations IC50 of CuCl2, (C9H6NO)2Cu and [Cu(phen)2]Cl2⋅6H2O were 9.9 × 10−4, 2.0 × 10−4, and 2.6 × 10−4 mol/L, respectively. The sequence of antibiotic activity of these three complexes was: (C9H6NO)2Cu > [Cu(phen)2]Cl2⋅6H2O > CuCl2. The growth rate constants of [Cu(phen)3]Cl2⋅6H2O did not change obviously with the increase of concentrations, but [Cu(phen)3]Cl2⋅6H2O also can prolong the time of Tetrahymena growth.  相似文献   

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