Effects of bacteriophage M13 infection upon phospholipid and fatty acid compositions ofEscherichia coli

Escherichia coli K38 were grown and infected with wild type and amber mutants of bacteriophage M13 in the early log phase. Lipid compositions of the infected and healthy cultures, grown under identical conditions, were determined 2 hr after infection. From the results, it was observed that total lipid and total phospholipid content remained nearly constant, suggesting that the cell membrane which contained the maximum phospholipids was not damaged by the infection. Moreover, the percentage of diphosphatidylglycerol and lyso-compounds corresponding to phosphatidylethanolamine and phosphatidylglycerol increased, while phosphatidylethanolamine and phosphatidylglycerol decreased. The increase in lyso-compounds may be due to the release of phospholipase A₂ (a periplasmic enzyme) from the cell wall after damage by the infection. Bacteriophage M13 infection had no effect on the fatty acid composition of the phospholipids.     

Metabolism of 12-ketooctadecanoic acid byEscherichia coli K-12 andCandida tropicalis

The mode of degradation of long chain keto acids by two microorganisms was investigated.Escherichia coli K-12 converted 12-ketooctadecanoic acid to 4-ketodecanoic acid, accumulating some amounts of intermediates, 10-ketohexadecanoic, 8-ketotetradecanoic and 6-ketododecanoic acids. In contrast,Candida tropicalis completely metabolized the keto acid with transient accumulation of the metabolites mentioned above. The difference between the metabolism byE. coli of hydroxy acid and keto acid is that 12-hydroxyoctadecanoic acid is degraded as far as 6-hydroxydodecanoic acid, while 12-ketooctadecanoic acid can be degraded as far as 4-ketodecanoic acid.     

E. coli K-12琥珀酸脱氢酶sdhC基因纳米锥的设计及自组装

采用DAEDALUS软件,以E. coli K-12 MG1655的琥珀酸脱氢酶复合体C亚基编码酶基因sdhC的双链DNA为脚手架链,进行一个边长为17.68 nm的正四面锥设计,并最终通过核酸自组装反应获得了sdhC基因的纳米锥聚合体。利用琼脂糖凝胶电泳、扫描电子显微镜和透射电子显微镜对多组样品进行化学组分和形貌分析,同时利用原子力显微镜液下成像法测定了核酸聚合体的三维尺度。结果表明：DAEDALUS软件设计出的16条订书钉链,确实将624 bp的sdhC双链DNA中的一条链折叠成了平均边长为19.05nm的正四面锥,与预设模型仅相差1.37nm,证明普通基因的双链DNA可以替代M13mp18单链核酸作为DNA折纸的核酸材料,为构建核酸纳米材料提供了一种新方法。     

Influence of ionic liquids on the growth ofEscherichia coli

Ionic liquids are compounds that composed only of ions and are liquid at room temperature. Thus, it is normally named room temperature ionic liquid (RTIL). In this study, the application of RTILs to the extractive fermentation of biomaterials was investigated as a substitute of organic solvents. The relative toxicity of the RTILs on the growth ofE. coli was tested. The inhibition of cell growth in the presence of various ionic liquids was measured using solid and liquid culture, and EC₅₀ of each RTILs was calculated. The number of viable and total cells was measured by the number of colonies and optical density, respectively. Effective concentrations of toxicity (EC₅₀) in these tested systems were similar with conventional solvents, such as acetone, acetonitrile, and ethanol. The viability ofE. coli was affected by the polarity and ionic properties of ionic liquids. The resistance of the microorganisms against ionic liquids was different with the cations and anions composing ionic liquids. No general influence of the anionic compound of the ionic liquids was found on toxicity comparing with distinctive influence of cationic moiety.     

Lipids of cultured hepatoma cells: IV. Effect of serum and lipid upon cellular and media neutral lipids

Minimal deviation hepatoma 7288C cells were cultured in a modified Swim's medium supplemented with decreasing levels of serum, lipid-free serum, lipid-free serum plus fatty acids, and other additives. Cellular and media neutral lipid classes were quantitated, the fatty acids of triglycerides and sterol esters analyzed, and the carbon number distribution of triglycerides determined. Cellular triglyceride biosynthesis virtually was inhibited when the medium was supplemented with bovine serum alone. This inhibition was not observed when the medium was supplemented with fetal calf serum alone or mixtures of fetal calf serum and bovine serum. Cells cultivated on medium supplemented with lipid-free serum plus palmitic or linoleic acids had much lower levels of free and esterified cholesterol. The fatty acid composition of cellular triglycerides and cholesterol esters differed dramatically from the corresponding media lipid classes. Except when linoleic acid was added to the medium, changes in the media serum and lipid levels had only marginal effects upon the fatty acid composition of cellular triglycerides and cholesterol esters. These data, in conjunction with earlier data that showed the media neutral lipid levels did not decrease during cell growth, indicate that these hepatoma cells utilize little or no serum triglycerides and cholesterol esters. Linoleic acid added to the medium dramatically reduced the level of 18∶1 acids in cellular triglycerides and cholesterol esters. Palmitic acid added to the medium did not change the fatty acid compositions significantly. Comparison of experimentally determined and calculated triglyceride carbon number percentages indicated a random distribution of fatty acids in this glyceride. The fatty acid composition of cellular triglycerides was similar to the composition of the cholesterol esters. The lack of characteristic and distinguishable compositions of these two classes that occur in most normal tissues suggests a loss of specificity in the lipid metabolism of this neoplasm at the class level.     

Influence of different reactor types on Nannochloropsis oculata microalgae culture for lipids and fatty acid production

Greenhouse gases emitted into the atmosphere by burning of fossil fuels cause global warming. One option is obtaining biodiesel. Nannochloropsis oculata was cultured under different light intensities and reactors at 25°C for 21 days with f/2 medium to assess their effects on cell density, lipid, and fatty acids (FAs). N. oculata improved cell density on fed-batch glass tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, yielding 3.5 × 10⁸ cells ml⁻¹, followed by fed-batch Erlenmeyer flask (1 L) at 650 μmol E m⁻² s⁻¹ with 1.7 × 10⁸ cells ml⁻¹. The highest total lipid contents (% g lipid × g dry biomass⁻¹) were 44.4 ± 0.8% for the reactor (1 L) at 650 μmol E m⁻² s⁻¹ and 35.2 ± 0.2% for the tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹, until twice as high compared with the control culture (Erlenmeyer flask 1 L, 80 μmol E m⁻² s⁻¹) with 21.2 ± 1%. Comparing the total lipid content at 200 μmol E m⁻² s⁻¹, tubular reactor (7 L) and reactor 1 L achieved 35.2 ± 0.2% and 28.3 ± 1%, respectively, indicating the effect of shape reactor. The FAs were affected by high light intensity, decreasing SFAs to 2.5%, and increased monounsaturated fatty acids + polyunsaturated fatty acids to 2.5%. PUFAs (20:5n-3) and (20:4n-3) were affected by reactor shape, decreasing by half in the tubular reactor. In the best culture, fed-batch tubular reactor (7 L) at 200 μmol E m⁻² s⁻¹ contains major FAs (16:0; 38.06 ± 0.16%), (16:1n-7; 30.74 ± 0.58%), and (18:1n-9; 17.15 ± 0.91%).     

Pulmonary lipid peroxides and fatty acids of rats fed different lipids and exposed to oxygen at hyperbaric pressure

Semipurified diets containing different lipids were fed to rat dams during lactation and subsequently to their pups for 33 weeks post-weaning. Some rats within each group were exposed to oxygen at hyperbaric pressure (OHP). Lipid peroxide levels were lower in lungs of rats fed 7% hydrogenated coconut oil or 10% butter as compared with their controls, fed 7% corn oil or 10% safflower oil, respectively. Exposure to OHP increased lung peroxide levels. This increase varied with the type of fat in the diet. Studies of the fatty acid composition indicate that lipid peroxide levels generally increased with an increase in the levels of 18∶2 in lung total lipids. The results suggest that the type of dietary lipid may alter the susceptibility of the animal to pulmonary oxygen toxicity.     

洗衣机洗涤参数对不同污渍洗净性能的研究

采用不同洗涤条件对3种标准污染布进行洗涤,比较污染布洗净率的变化。实验表明,家用滚筒洗涤对皮脂污染布的洗净率较高,对蛋白污染布的洗净率较低。40℃洗涤温度是3种污染布比较合适的洗涤温度,洗涤时间45min是比较合适的主洗时间,洗涤转速50r/min是较合适的主洗转速;转停比较小时,对污染布的洗净率无显著影响;转停比较大时,对污染布的洗净率有显著影响,20∶10为较佳转停比。     

Conversion of lipids upon the mechanical degradation of lacustrine sediments

The effect of the mechanical treatment of lacustrine sediments in mechanical activators of various designs on the degree of dispersion, the yields of free and bound lipids, and the carotenoid and chlorophyll contents of lipids was studied. A comparative analysis of changes in the composition of lipids upon the acid and mechanical treatments of lacustrine sediments was performed.     

Effects of dissolved oxygen control on cell growth and exopolysaccharides production in batch culture ofAgaricus blazei

To investigate the effects of DOC on cell growth and EPS production, DOC was controlled at three different levels of 10, 20, and 40% of air-saturation by manipulating agitation speed in a series of batch cultures ofA. blazei. The cellular and EPS productivities increased with the DOC level up to 20%. However, DOC had no significant effects over 20%. When DOC was controlled at 20%, the cellular and EPS productivities were observed to increase 1.6-fold and 2.2-fold, respectively, as compared to the control case with no DOC control in which DOC dropped to and there-after remained at almost zero. Another batch culture was carried out with the DOC controlled at 20% by manipulating the amount of oxygen supply at a rather low agitation speed of 100 rpm. In this case, the cellular productivity was comparable to that of the former case in which DOC was controlled at the same level of 20% by manipulating agitation speed in the range of 100–450 rpm. However, the EPS productivity was about 15% lower than the former case, implying that a sufficient level of agitation is also important for EPS production.     

Effects of polarity and pH on the solubility of acid-treated carbon nanotubes in different media

The aggregation of acid-treated carbon nanotubes (CNTs) as a solid and their solubility in solvents of different polarity and in water of different pH were investigated as a function of acid treatment conditions. The CNTs were found to form solid hydrogen-bonded aggregates, with a higher content of COOH groups resulting in a denser aggregate. The untreated CNTs were non-polar in nature and could dissolve, or be easily dispersed, in non-polar or low polar solvents such as acetone and alcohols (methanol and ethanol), but precipitated from deionized water, a highly polar solvent. In contrast, the acid-treated CNTs dissolved or were well dispersed in the deionized water, but not in acetone or alcohols. The treated CNTs were insoluble in an aqueous solution of pH 0, but soluble in those of pH 4 and higher with their solubility monotonically increasing with pH up to pH 10. The considerable ionic bond strength between carboxylate anions and sodium cations could be a reason for a decrease of their solubility in an aqueous solution of pH 12.     

Formulation and optimization of two culture media for the production of tumour necrosis factor-β in Escherichia coli

Two culture media were designed and optimized by statistical techniques for the growth of Escherichia coli K12 HB101 (pCG402) which expressed human tumour necrosis factor-β (TNF-β). Common compounds, such as MgSO₄ and KH₂PO₄, were used to provide the bacteria with the necessary elements for biomass synthesis. For compounds not required for biomass synthesis, such as thiamine, or compounds used for both biomass synthesis and as an energy source, such as glucose, yield coefficients were used. In formulating the composition of the nutrients, carbon was chosen as the limiting substrate in both media. In the complex medium (CM), casein hydrolysate was selected to supply the two auxotrophic amino acids, proline and leucine. The optimal ratio of glucose to casein hydrolysate was determined to be 1:0·6 by using a centre composite design experiment. In the defined medium (DM), the concentrations of the three carbon sources, glucose, proline and leucine were based on their respective yield coefficients (Y_{biomass/glucose}: 0·5, Y_{biomass/proline}: 7, Y_{biomass/leucine}: 13·5). Shake flask experiments based on a fractional design were used to confirm that the two media were glucose limiting. Bacterial growth was improved in CM whereas DM gave higher TNF-β expression. A 2-dm³ fed-batch fermentation using CM was performed and a dry biomass concentration of 20 g dm^?3 was obtained with the expression of soluble TNF-β being 20 mg g^?1 dry biomass. With this fed-batch system, a high biomass concentration and high expression of TNF-β were achieved concomitantly.     

Intake of different eicosapentaenoic acid-containing lipids and fatty acid pattern of plasma lipids in the rats

The ethyl ester of eicosapentaenoic acid (EPA) is the only pure EPA-containing lipid available in bulk for oral administration. However, there is doubt as to whether EPA ethyl ester can efficiently increase the plasma levels of EPA in comparison with the ability of other kinds of EPA-containing lipids to do so. Therefore, two other kinds of EPA-containing lipids were prepared to study the efficiency of oral administration of those lipids for increasing the EPA content in plasma phospholipids and cholesteryl esters. EPA-containing lipids which were investigated were [A], 1,2,3-trieicosapentaenoyl-glycerol, [B] 2-eicosapentaenoyl-phosphatidylcholine and [C] ethyl ester of EPA. An adjusted amount of lipids [A], [B] and [C] was administered to rats through a gastric tube for 4 days (the first experiment) or for 10 days (the second experiment), and the fatty acid composition of plasma phospholipids and cholesteryl esters was determined. In the first experiment, there were no significant differences in the efficiency for increasing EPA levels in either phospholipids or cholesteryl esters among the lipids. In the second experiment, the EPA levels of both plasma phospholipids and cholesteryl esters of rats administered ethyl ester of EPA were significantly higher than those of rats administered 2-eicosapentaenoyl-phosphatidylcholine. The EPA levels of the rats administered 1,2,3-trieicosapentaenoylglycerol were between the levels of the two groups mentioned above, but the differences in the EPA levels were not significant. Although an ethyl ester-type molecule is not a naturally occurring lipid, ethyl ester of EPA is equal to 1,2,3-trieicosapentaenoyl-glycerol and appears to be superior to 2-eicosapentaenoyl-phosphatidylcholine as to the efficiency for increasing EPA levels in total plasma phospholipids and plasma cholesteryl esters.     

Effect of oxygen levels on the fatty acids and lipids ofMucor rouxii

The effect of aerobic and oxygen limiting (anaerobic) growth conditions upon the fatty acid and lipid composition ofMucor rouxii has been examined. The aerobic cells contained a range of fatty acids typical of phycomycetes, i.e. γ-linolenic acid, with an unsaturation index of 1.20, whereas the anerobic cells contained relatively high levels of shorter chained fatty acids and very low concentrations of unsaturated acids (unsaturation index=0.025). The unsaturated compounds were monoolefinic tetra-, hexa-, and octadecenoic acids; and closer examination of their di-trimethylsilyl derivatives by gas chromatography and mass spectrometry showed that all three acids contained the double bond in the Δ⁹ position. These results were consistent with a microaerobic biosynthetic pathway. In addition, there were major quantitative differences in the lipid composition of the two types of cells; and it was evident that the differences in growth environment markedly affected the cellular lipid and fatty acid compositions.     

Partial purification and conversion of the particulate-bound diglyceride kinase ofEscherichia coli to a water soluble,detergent free state

Alkali (pH 11.5) treatment of a washed, ammonium sulfate-precipitated residue derived from a triton-X-100 extract of a 30,000 Xg particulate diglyceride kinase preparation ofE. coli converts much of the enzyme to a 100,000 Xg soluble, detergent free state. This procedure improves the enzyme as an analytical tool for the structural analysis of triglycerides, and may be applicable for the solubilization of the many other glyceride- and phosphoglyceride-forming enzymes which have all resisted further purification because of insoluble, particulate properties.     

In vivo and in vitro biosynthesis of free fatty alcohols inEscherichia Coli K-12

In vivo studies have indicated that exogenous free fatty acids may serve as precursors of the free fatty alcohols ofEscherichia coli K-12. Following disruption of the cells, the enzymatic activity capable of catalyzing the reduction of long chain fatty aldehydes to fatty alcohols was localized in the 100,000 x g supernatant fraction. Nicotinamide adenine dinucleotide phosphate, reduced form, was the required cofactor. The product of the reaction was characterized rigorously as 1-hexadecanol when hexadecanal was the substrate. Three independent, but complementary, assay methods were developed to assay the aldehyde reductase activity. By employing these methods, an equivalence between nicotinamide adenine dinucleotide phosphate, reduced form, oxidation and 1-hexadecanol synthesis was established. Two protein fractions catalyzing the reduction of fatty aldehydes to fatty alcohols were detected in the 100,000 x g supernatant fraction following ammonium sulfate fractionation and diethylaminoethyl-cellulose chromatography. Enzymatic activity (70%) applied to the diethylamino-ethyl-cellulose column was eluted at a phosphate concentration of 0.115 M. The remaining 30% was eluted at a concentration of 0.23 M. Following sephadex chromatography, it was observed that the enzyme eluting at 0.115 M phosphate had an apparent mol wt of 250,000 Daltons while that eluting at 0.23 M had an apparent mol wt of 62,000 Daltons. The enzymes were similar with respect to substrate specificity, pH optima, ionic strength optima, and stability with respect to thiol inhibitors, suggesting different sized aggregates of similar subunits.