不同浓度铜对紫背萍和青萍色素含量及抗氧化酶系统的影响

通过水培试验研究了不同浓度的重金属Cu对紫背萍(Spirodela polyrrhiza)和青萍(Lemna minor)的色素含量和抗氧化酶系统的影响.结果表明,低浓度Cu(0.056 mg·L^-1)的处理下,紫背萍和青萍的叶绿素a、叶绿素b和叶绿素(a+b)的含量均出现不同程度的增加,分别高出其对照11％、46％、22％和8％、15％、11％,而在高浓度Cu(0.18～5.60 mg·L^-1)的处理下,上述色素含量均显著下降,平均下降幅度分别达63％、62％、65%和46％、44％、45％.紫背萍体内丙二醛(MDA)含量为青萍的2.57倍.两种浮萍的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)的活性均随Cu浓度的增加而呈先升后降的趋势,紫背萍体内3种酶活性在Cu浓度仅为0.18 mg·L^-1时即达峰值,随后则大幅下降,而青萍体内3种酶活性却在Cu浓度分别升高到0.56、1.0和1.0 mg·L^-1时才达到峰值.可见,在Cu胁迫下,紫背萍受Cu毒害较青萍深,且其体内抗氧化酶系统也较青萍敏感.     

Cr6+和乙草胺对少根紫萍的毒性效应

采用水培实验方法,研究了重金属Cr6 和除草剂乙草胺对少根紫萍(Spirodela oligorrhiza L.)生长的单一毒性和联合毒性效应.结果表明,Cr6 和乙草胺对少根紫萍96 h生长抑制的IC50分别为15.4和6.95 mg* L-1,在质量浓度1∶ 1的情况下, Cr6 与乙草胺共存对少根紫萍96 h的IC50 为3.14 mg* L-1,二者为协同作用.随着Cr6 和乙草胺处理浓度的增加,少根紫萍叶绿素a浓度下降,复合污染对叶绿素a的影响明显大于单一污染,也表现为协同作用.另外,还对少根紫萍生长抑制实验进行了探讨,建议使用植物个体数和重复间的偏差作为衡量实验质量的指标.     

Large‐scale screening and characterisation of Lemna aequinoctialis and Spirodela polyrhiza strains for starch production

• Duckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. Selection of duckweed strains with high starch accumulation is essential for application of duckweeds to bioethanol production. Geographic differentiation had a large influence on genetic diversity of duckweeds.
• Biomass production, starch content and starch amount in geographically isolated strains of 20 Lemna aequinoctialis and Spirodela polyrhiza were calculated to evaluate their potential for bioethanol production. The influence of different collection time, culture medium and NaCl concentration on starch accumulation of the best strains were analysed.
• The results showed that biomass production, starch content and starch production of duckweeds demonstrated clonal dependency. The best strain was L. aequinoctialis 6000, with biomass production of 15.38 ± 1.47 g m^?2, starch content of 28.68 ± 1.10% and starch production of 4.39 ± 0.25 g m^?2. Furthermore, starch content of L. aequinoctialis 6000 was highest after 8 h of light, tap water was the best medium for starch induction, and NaCl did not induce starch accumulation.
• This study suggests duckweed biomass production and starch production demonstrate clonal dependency, indicating that extensive clonal comparisons will be required to identify the most suitable isolates for duckweed selective breeding for bioethanol.

     

紫萍磷转运蛋白1;1 cDNA序列的克隆及表达模式

紫萍Spirodela polyrrhiza是一种在生物质资源开发利用和水体生物修复中广泛使用的漂浮植物.随着水体富营养化日益严重,紫萍在水面随处可见.有文献报道紫萍对水体中的氮和磷有良好的净化作用.为了深入研究紫萍对水体中无机磷的吸收和转运,以紫萍为材料提取RNA反转录为cDNA,以此为模板,扩增得到1条特异性片段,...     

Isotherm and kinetic modelling of Toluidine Blue (TB) removal from aqueous solution using Lemna minor

The aim of this study was to investigate the ability of Lemna minor for Toluidine Blue (TB) removal. Influence of the initial concentration over the removal process was considered. Experimental data have been analyzed using Langmuir, Freundlich, Dubinin–Radushkevich (D–R), and Elovich isotherm models. In addition, several kinetic models, pseudo-first-, pseudo-second-order, intraparticle and film diffusion models were considered. Langmuir and Freundlich isotherm suggested a favorable adsorption of TB by Lemna minor plants. From the D–R the mean free energy was calculated to be 11.18 kJ/mol, which indicates that TB adsorption was characterized by a chemisorption process. Kinetic studies showed that liquid film diffusion plays an important role during the process. Adsorption capacities of up to 26.69 mg/g and a high capacity of adaptation indicated that phytoremediation using Lemna minor could be a valuable alternative for dyes removal from wastewaters.     

A HPTLC densitometric determination of flavonoids from Passiflora alata, P. edulis, P. incarnata and P. caerulea and comparison with HPLC method

A high-performance thin layer chromatographic (HPTLC) method was developed in order to determine quantitatively the flavonoids in leaves of Passiflora alata, P. edulis, P. caerulea and P. incarnata. The content of orientin and isoorientin was determined, and the results were compared with those obtained using a quantitative HPLC-UV method. The latter employed rutin as standard and was developed to analyse flavonoid content from Passiflora leaves for the purpose of ensuring the quality of Passiflora phytomedicines. The results obtained using the two methods indicate that there are qualitative and quantitative differences in the flavonoids of the reference Passiflora species studied. The two methods were also employed to analyse commercial samples to illustrate their application in qualitative ('fingerprint') and quantitative determination, demonstrating their feasibility in the quality control of flavonoids from crude Passiflora drugs and phytomedicines. The HPLC conditions used are also suitable for the quantitative analysis of aqueous extracts (Passiflora infusions).     

Compartmental analysis of Rb+ efflux from roots of intact high-salt barley plants

The validity of compartmental analysis of Rb⁺ efflux from roots of intact high-salt barley plants ( Hordeum vulgare L. cv. Salve) was examined. ⁸⁶Rb⁺ was used as a tracer. Rb⁺ (1 m M ) was included together with 3 m M K⁺ in the growth medium, and steady-state conditions were assumed to prevail during the experiment. Three phases of efflux were revealed with half-times of 23 min, 109 min and 12 h, respectively; and the time span of the experiment had to be at least 20 h to make determination of the slow phase possible. We cannot state what compartments in the root the 3 different slopes represent. A comparison of slopes was made between the plots of In efflux vs time and In content vs time. In spite of correction for tracer transport from the roots to the shoot, the slopes for the slow phase did not agree unless up to 85% of the root content of Rb⁺ is assumed not to participate in efflux.     

Carbohydrate partitioning, photosynthesis and growth in Lemna gibba G3. II. Effects of phosphorus limitation

The relationship between CO₂ assimilation rate, growth and partitioning of carbon among starch, sucrose, glucose and fructose were studied in phosphorus (P_i)-limited Lemna gibba L. G3. Two experimental models were used: 1) Cultures were grown at various stable, suboptimal rates regulated by the supply of P_i; 2) cultures growing at optimal rates were transferred to P_i-free medium. The response to a P_i deficiency can be divided into two phases. Phase I is characterized by hyperactivity of the sucrose synthesis pathway, leading to high levels of glucose and fructose. Phase II is characterized by starch accumulation associated with a decrease in the cytoplasmic pools of soluble sugars owing to inhibition of carbon export from the chloroplast. A strong negative correlation was found between the CO₂ assimilation rate and starch levels. No significant correlation was found between assimilation and ATP levels and decrease in relative growth rate did not significantly affect the adenylate energy charge (EC). The regulatory aspects of the partitioning of carbon among soluble sugars and starch as well as the negative correlation between carbohydrate levels and CO₂ assimilation at P_i-limited growth are discussed.     

The influence of phosphate nutrition on H ion efflux from the roots of young rape plants

Changes in pH around the roots of young rape plants were studied using a nutrient film technique which allowed either part or all of the root system to be subjected to specific nutrient treatments. The rapidity and direction of change of pH was assessed by embedding absorbing roots in a thin layer of agar containing bromocresol purple. Measurements were also made with a pH microelectrode placed next to the roots. Phosphate-fed plants were deprived of phosphate when 14 days old. Patterns of pH changes round the deprived roots were the same as with phosphate-fed plants until the plants had been deprived of P for three days, when H ion efflux started in the terminal portions of the roots. The lengths of root producing acid and amounts of H ion both increased as the plants became more P deficient. Both P fed and P deprived roots produced HCO₃ ions but the net amount of HCO₃ ion produced by the P deficient roots fell as did nitrate uptake rates. Cation-anion balances measured at the end of the experiment showed that uptake of all anions and K decreased in the P deprived plants but uptake of Ca and Mg were little altered. This resulted in a smaller ratio of anions to cations absorbed which was reflected in the reduced HCO₃ ion efflux.     

响应面优化紫萍黄酮提取工艺及其抗氧化活性

采用响应面法优化微波提取紫萍黄酮的条件。在单因素实验的基础上,选取乙醇体积分数、微波功率、液料比为影响因子,应用Box-Behnken中心组合法进行三因素三水平的试验设计,以紫萍黄酮得率为响应值,进行响应面分析(RSM),结果表明:微波提取紫萍黄酮的最佳提取条件为乙醇体积分数62%、液料比17∶1(mL/g)、微波功率500 W、微波时间9 min;在优化工艺下,紫萍黄酮的得率达到4.14%。对微波提取的紫萍黄酮进行抗氧化性研究发现紫萍黄酮对DPPH.清除作用较好,其抗氧化活性要优于相同浓度的抗坏血酸(VC)和2,6-二叔丁基对甲酚(BHT)。     

Dynamics of CO2 efflux from the substrate root system of container-grown plants associated with irrigation cycles

In intensive horticultural crops, the choice of growing media and the adequate management of irrigation must ensure an optimal trade-off between aeration and water supply to roots. The proportion of gas-filled pores and their composition can be strongly affected by the water status and hence by irrigation. In this context, continuous measurement of gas exchange and water status of the growing medium could bring out some insights into how irrigation events affect root activity and aeration in a time scale of minutes to several hours. For this purpose, a measuring system was developed that measured the CO₂ efflux rate from the entire substrate root system of pot plants while their shoots were kept outside, undisturbed. It was able to monitor four plants at a time for several weeks at a rate of one measurement per plant every 10 min, thus tracing the dynamics of CO₂ efflux through a great many irrigation cycles. The results showed a marked pattern of CO₂ efflux around each irrigation event, consisting mainly of a sharp, conspicuous peak followed by a depression until a threshold in substrate water potential was reached. Analysis of these data suggests that the pattern is imposed mainly by the effects of irrigation and water content on the mobility of gases in the growing medium. The peak can be explained by the CO₂-enriched air being displaced by the water added to the growing medium in the pot, and the following depression can be the result of the reduced mobility of gases when substrate water content is high. In spite of the great variation in the instantaneous efflux rate of CO₂, the integration of these CO₂ values for the entire day provides a rather predictable value given the root biomass and does not seem to be affected by the number of irrigation events that occur in a given day.     

Effect of pH,Temperature, and Lead Concentration on the Bioremoval of Lead from Water Using Lemna Minor

This study examined the ability of the aquatic plant Lemna minor (duckweed) to remove soluble lead under various laboratory conditions. In a batch process L. minor was exposed to different pH values (4.5–8.0) and temperature (15–35°C) in presence of different lead concentrations (0.1–10.0 mg L^?1) for 168 h. The amount of biomass obtained in the study period on a dry weight basis, the concentrations of lead in tissue and in medium and net uptake of lead by Lemna all have been determined in each condition. The percentages of lead uptake ratios (PMU) and bioconcentration factors (BCF) were also calculated for these conditions. Bioaccumulated lead concentrations and the PMU were obtained at lowest pH of 4.5, and at 30°C. The highest accumulated lead concentration was found at pH 4.5 as 3.599 mg Pb g^?1 in 10.0 mg L^?1. It decreased to pH 6.0, but it did not change at pH 6.0–8.0 range. The maximum lead accumulation was obtained at 30°C as 8.622 mg Pb g^?1 in 10 mg L^?1 at pH 5.0, and the minimum was at 15°C as 0.291 mg g^?1 in 0.1 mg L^?1. Lead accumulation gradually increased with increasing lead in medium, but the opposite trend was observed for PMU. Lead accumulation increased up to 50 mg L^?1, but did not change significantly in the 50.0–100.0 mg L^?1 range. The lead uptake from water was modeled and the equation fit the experimental data very well.     

Phosphate efflux from jejunal enterocytes of the rat: effect of phosphate concentration gradient and pH.

The effect of variation in the intracellular and extracellular phosphate concentration on the Pi efflux across the basolateral membrane of pre-loaded enterocytes has been examined. Efflux rate constants for Pi fell from 0.89 h-1 to 0.68 h-1 as the extracellular Pi concentration was increased from 0.5 mM to 5 mM. As the intracellular Pi concentration was raised from 0.5 to 3 mM the rate constant dropped from 0.95 h-1 to 0.77 h-1. The findings are indicative of the presence of Pi-specific transporter at the basolateral membrane. The efflux rate constant of Pi at pH 7.1 was higher than that at pH 7.4 suggesting that the Pi flux across the basolateral membrane of enterocytes follows a similar pattern towards pH changes as do fluxes across the brush-border membrane.     

The production-influencing factors of extracellular polysacchadde(EPS) from a Strain of lactic acid bacteria and EPS extraction

The influencing factors of extracellular polysaccharide(EPS)produced from a strain of lactic acid bacteria(LAB L15)were studied by using the phenol-H2SO4 method.It was demonstrated that the strain produced EPS at the most amount when it was incubated for 40-48 h and when the pH value was 4 under 30℃.Glucose was the most suitable carbon source for LAB-producing EPS.The rough EPS was obtained from L15 culture after centrifugation,dialysis,deprotein,decoloration,and ethanol-precipitation.The sample was at least composed of two polysaccharides mat were completely different in molecular weight and the amount.The purified EPS was passed through the SephadexG-200 colunm and it showed that it was a sample purified by thin layer chromatography.     

The production-influencing factors of extracellular polysaccharide (EPS) from a strain of lactic acid bacteria and EPS extraction

The influencing factors of extracellular polysaccharide (EPS) produced from a strain of lactic acid bacteria (LAB L15) were studied by using the phenol-H₂SO₄ method. It was demonstrated that the strain produced EPS at the most amount when it was incubated for 40–48 h and when the pH value was 4 under 30°C. Glucose was the most suitable carbon source for LAB-producing EPS. The rough EPS was obtained from L15 culture after centrifugation, dialysis, deprotein, decoloration, and ethanol-precipitation. The sample was at least composed of two polysaccharides that were completely different in molecular weight and the amount. The purified EPS was passed through the SephadexG-200 column and it showed that it was a sample purified by thin layer chromatography. __________ Translated from Microbiology, 2005, 32(4): 85–90 [译自: 微生物学通报, 2005, 32(4): 85–90]     

ABCG1 mediated oxidized LDL-derived oxysterol efflux from macrophages

Objectives

The uptake of oxidized LDL (oxLDL) by macrophages is a key initial event in atherogenesis, and the removal of oxidized lipids from artery wall via reverse cholesterol transport is considered antiatherogenic. The aims of this study were to investigate the pathways mediating the removal of oxysterols from oxLDL-loaded macrophages, and the subsequent uptake of the oxysterols by hepatocytes.

Methods

LDL was labeled with [3H]cholesterol, and LDL-[3H]cholesterol was oxidized by copper using a standard method. [3H]oxysterol formation in oxLDL was analyzed by thin layer chromatography. oxLDL-[3H]sterol was incubated with macrophages, allowing the uptake of [3H]sterol by macrophages. [3H]sterol efflux from macrophages mediated by ATP binding cassette transporters (ABCA1, ABCG1), or scavenger receptor class B type I (SR-BI) was measured. The subsequent uptake of the [3H]sterol by hepatocytes was also determined.

Results

7-Ketocholesterol was the major oxysterol formed in oxLDL, and it was significantly higher in oxLDL compared with that in native LDL (naLDL). oxLDL-derived sterol efflux to HDL from macrophages was significantly increased compared with naLDL-derived sterol, and it was mainly mediated by ABCG1, but not by ABCA1 or SR-BI. Moreover, although HDL dose-dependently induced sterol efflux from macrophages, only the exported sterol by ABCG1 pathway was efficiently taken up by hepatocytes.

Conclusions

ABCG1 mediates oxysterol efflux from oxLDL-loaded macrophages, and the exported oxysterol by ABCG1 pathway can be selectively taken up by hepatocytes.     

Molecular cloning and characterization of the HmrM multidrug efflux pump from Haemophilus influenzae Rd

We cloned a gene responsible for norfloxacin resistance from the chromosomal DNA of Haemophilus influenzae Rd, and designated the gene as hmrM. HmrM showed sequence similarity with NorM of Vibrio parahaemolyticus and YdhE of Escherichia coli and others that belong to the MATE family multidrug efflux pumps. The recombinant plasmid carrying the hmrM gene conferred elevated resistance not only to norfloxacin but also to acriflavine, 4 ', 6-diamidino-2-phenylindole, doxorubicin, ethidium bromide, tetraphenylphosphonium chloride, Hoechst 33342, daunomycin, berberine, and sodium deoxycholate in Escherichia coli KAM32, a drug-hypersensitive strain. We observed an Na+-dependent efflux of ethidium and an ethidium-induced efflux of Na+ in E. coli KAM32 cells harboring the plasmid carrying the hmrM gene. These results indicate that HmrM is an Na+/drug antiporter-type multidrug efflux pump. A difference in substrate preference was observed between HmrM, NorM, and YdhE.     

Isolation and characterization of a tetrasialoganglioside from mouse brain, containing 9-O-acetyl,N-acetylneuraminic acid

A new ganglioside, containing an alkali-labile linkage, was extracted from mouse brain and purified. It represents 3.6% of total lipid-bound sialic acid in the tissue and was obtained in pure form with a yield of about 35%. It contains sphingosine, glucose, galactose, N-acetylgalactosamine and sialic acid in the molar ratio 1:1:2:1:4 and, upon exhaustive sialidase treatment gives the monosialoganglioside GM1. Partial acid hydrolysis, methylation analysis, gas-liquid chromatography-mass spectrometry and chromium trioxide oxidation studies showed its basic neutral glycosphingolipid core to be ganglio-N-tetraose-ceramide. Three of the four sialic acid residues are N-acetylneuraminic acid and one, as shown by gas-liquid chromatography-mass spectrometry, is 9-O-acetyl,N-acetylneuraminic acid, which contains the alkali labile linkage. 9-O-acetyl,N-acetylneuraminic acid is -ketosidically linked to position 8 of the N-acetylneuraminic acid residue bound to position 3 of the internal galactose. The other two N-acetylneuraminic acid residues form a disialosyl residue linked to position 3 of external galactose. The complete structure of the studied ganglioside is as follows: NeuAc2–8NeuAc2–3Galβ1–3GalNAcβ1–4(9-O-Ac-NeuAca2–8NeuAc2-1′-N-acylsphingosine, and it can be considered as a derivative of the tetrasialoganglioside GQ1b.     

Growth and nitrate uptake properties of plants grown at different relative rates of nitrogen supply. I. Growth of Pisum and Lemna in relation to nitrogen

Abstract The relations between growth and internal nitrogen concentrations were investigated in nonnodulated Pisum sativum L. cv. Marma and Lemna gibba L. grown at relative rates of nitrate-N additions (R_A) varying from 0.03 to 0.27 d ¹(Pisum) and 0.05 to 0.40 d ¹ (Lemna). At R_A≤0.21 d ¹(Pisum) and ≤0.30 d ¹ (Lemna), the relative growth rate (RGR) correlated well with R_A whereas higher R_A was not met by any further increawse in growth rate. The tissue nitrogen concentrations at growth-limiting R_A increased linearly with RGR. The slope of these lines indicate a maximum nitrogen productivity (amount of biomass formed per unit nitrogen and time) of 14.4 g DW g ¹ Nd ¹ for Pisum and 15.9 g DW g ¹ N d ¹ for Lemna. Extrapolation of the plots to RGR=0 yielded intercepts of 10–15 mg N g^?1 DW for Pisum tissue, whereas for Lemna the intercepts were closer to the origin than for Pisum. These intercepts formally define a fraction of the total plant nitrogen that appears not to be active in production of new biomass, her termed ‘non-growth nitrogen’. The partitioning of nitrogen as well as biomass to the roots increased at low R_A, and is discussed in relation to activity of shoots and roots, respectively.     

Gene cloning and properties of the RND-type multidrug efflux pumps MexPQ-OpmE and MexMN-OprM from Pseudomonas aeruginosa

We cloned two operons for putative RND-type multidrug efflux pumps from Pseudomonas aeruginosa by a PCR method. We designated the genes in one operon mexPQ(-opmE) and in another operon mexMN. Introduction of the mexPQ-opmE into drug hypersensitive cells resulted in elevated MICs of macrolides, fluoroquinolones and some other drugs. Introduction of the mexMN into the hypersensitive cells possessing oprM, but not into cells not possessing oprM, resulted in elevated MICs of chloramphenicol and thiamphenicol. Thus, we conclude that MexPQ-OpmE and MexMN-OprM are functional multidrug efflux pumps when expressed in P. aeruginosa.