Determination of total copper and zinc contents of Egyptian soils using three different methods

Summary To compare chemical methods for determining total contents of Cu and Zn in Egyptian soils, surface samples of two groups of soils from Egypt namely the alluvial and the calcareous were chosen. The samples were analyzed for the total Cu and Zn using three chemical methods namely, aqua regia, hydrofluoric acid and fusion methods. The mean values of total Cu determined by aqua regia, hydrofluoric acid and fusion methods were 58.7, 69.2, 69.4 ppm for the alluvial soils and 11.8, 13.0, 12.8 ppm for the calcareous soils respectively. The corresponding values of Zn were 138.6, 189.4, 189.8 ppm for the alluvial soils and 58.6, 89.7, 90.3 ppm for the calcareous soils. The Cu and Zn contents in the alluvial and calcareous soils, determined by the aqua regia method was lower as compared with those determined by the fusion or hydrofluoric methods.An attempt was made to use the etching of soil with aqua regia and the linear relationship, to quantitavely evaluate the total content of Cu and Zn determined with hydrofluoric acid or fusion methods.     

Reaction of labelled65ZnCl2,65ZnEDTA and65ZnDTPA with different clay-systems and some alluvial Egyptian soils

Summary The clay fraction separated from an alluvial Egyptian soil and montmorillonite clay mineral were equilibrated with CaCl₂ or NaCl solution then treated with humic acid isolated from composted clover straw to obtain different clay systems: Ca-clay, Ca-clay-HA, Na-clay, Na-clay-HA, Ca-mont and Ca-mont-HA. These clays as well as seven soil samples were reacted with different amounts of labelled⁶⁵ZnCl₂,⁶⁵ZnEDTA and⁶⁵ZnDTPA. The effectiveness of these Zn-sources for maintaining soluble Zn²⁺ ions in the equilibrium solution was the greatest for ZnDTPA and the lowest for ZnCl₂. Ca-clay provided greater Zn sorption capacity than Na-clay, and complexing the clay with humic acid depressed its capacity for Zn sorption. At the pH of the clay-systems (pH=6.5), the possibilities of Zn(OH)₂ formation were reduced especially in the presence of Zn-chelates. Reactions of⁶⁵ZnE DTA and⁶⁵ZnDTPA with the seven soils produced higher levels of soluble Zn²⁺ ions in the equilibrium solution rather than⁶⁵ZnCl₂ meanwhile ZnDTPA was more effective than ZnEDTA. The calculated Zn(OH)₂ ion product in the solution of ZnCl₂-soil systems indicated the precipitation of Zn as Zn(OH)₂. However, this was not valid in the Zn-chelates-soil systems. The results also revealed the role of soil carbonate, organic matter and soil texture as soil variables affecting Zn sorption by natural soils.     

黄单胞菌P5310-luxAB菌株在水稻根际的吸附与土壤中的存活

目的研究标记菌株在水稻国丰1号幼根根表的吸附动态规律和不同类型土壤中存活情况,为禾本科植物凝集素介导作用、吸附的影响参数和联合固氮的研究及应用提供科学依据。方法采用三亲本杂交法将发光基因luxAB导入水稻根际促生菌黄单胞菌（Xanthom onassp）P5310菌株中,标记菌株P5310-luxAB能稳定遗传,luxAB基因的导入不影响标记菌株生长特性。结果 P5310-luxAB菌株存在稳定型和松散型两种吸附,随标记菌株浓度变化的吸附规律符合Langmu ir等温吸附方程,水稻根表最大吸附量qm=3.33×109CFU/g,吸附系数α=2.86×10-8。凝集素处理的水稻根表对标记菌株的亲和力增强,吸附量也随之增大。标记菌株在灭菌土壤和不灭菌土壤中都能很好的存活。在前25 d,不灭菌土壤中菌落数要低于灭菌土壤,随着营养的消耗,细菌明显减少;但补充营养后,在灭菌土壤和不灭菌土壤中标记菌株数量都快速增加,证明标记菌株与不灭菌土壤中的土著微生物的竞争占优势,很快与灭菌土壤中的菌数接近,证明菌株能在土壤中很好地存活与定植。结论以上研究结果为菌株P5310的开发应用提供了可靠的实验数据。     

A comparison of electro-ultrafiltration and quantity/intensity measurements of soil potassium with its uptake by ryegrass in Scottish soils

Summary Electro-ultrafiltration (EUF) and quantity/intensity (Q/I) parameters of soil K were compared for 14 soils from each of three soil series. The K desorbed by EUF during the first 10 min (K₁₀) was closely correlated with the equilibrium activity ratio (AR₀) for soils of the same series, but differences between series reflected the soil K-buffering capacity, indicating that K₁₀ includes loosely held exchangeable K and is not strictly an intensity measurement. EUF values were compared with conventional soil test methods for predicting K-uptake and dry-matter yield of ryegrass grown in the glasshouse. Correlation coefficients between K uptake at the first cut were 0.80 for K₁₀, 0.88 for K_a (the initially labile K derived from the Q/I curve), 0.92 for K₃₅ (desorbed by EUF in 35 min) and 0.97 for K_ex (1.0M ammonium acetate extraction).     

The adsorption and release of tylosin by clays and soils

Summary The uptake and release of tylosin by Wyoming bentonite, Ca⁺⁺ montmorillonite, illite (Fithian Illinois) and kaolin (china clay) was studied. The adsorption capacities of bentonite and montmorillonite for tylosin were found to be 190 and 65 g mg^–1 respectively, while the adsorption capacities of illite and kaolinite were found to be 22 and 6.5 g mg^–1. 7.6 and 7.4% respectively of the tylosin adsorbed by bentonite and montmorillonite, and 30 and 25% respectively of the tylosin adsorbed by illite and kaolinite, was released in phosphate buffer.The presence of tylosin in two different soils amended with tylosin fermentation waste was also studied, and the effect of temperature on tylosin release was examined in one of the soils. The concentration of tylosin in the soil water was found to be related more to the concentration of tylosin fermentation waste than to the incubation temperature. The amounts of tylosin present in the initial leachates of the two soils, a modified John Innes compost and a limestone waste, were found to be in excess of the minimum inhibitory concentrations for susceptible bacteria. It is hypothesised that in these particular soils if the tylosin is not broken down by microbial action it could affect susceptible populations of bacteria.     

Immobilization of glucoamylase by adsorption on carbon supports and its application for heterogeneous hydrolysis of dextrin

Glucoamylase (GA) was immobilized by adsorption on carbon support: on Sibunit, on bulk catalytic filamentous carbon (bulk CFC) and on activated carbon (AC). This was used to prepare heterogeneous biocatalysts for the hydrolysis of starch dextrin. The effect of the texture characteristics and chemical properties of the support surface on the enhancement of the thermal stability of the immobilized enzyme was studied, and the rates of the biocatalyst's thermal inactivation at 65-80 degrees C were determined. The thermal stability of glucoamylase immobilized on different carbon supports was found to increase by 2-3 orders of magnitude in comparison with the soluble enzyme, and decrease in the following order: GA on Sibunit>GA on bulk CFC>GA on AC. The presence of the substrate (dextrin) was found to have a significant stabilizing effect. The thermal stability of the immobilized enzyme was found to increase linearly when the concentration of dextrin was increased from 10 wt/vol % to 50 wt/vol %. The total stabilization effect for glucoamylase immobilized on Sibunit in concentrated dextrin solutions was about 10(5) in comparison with the enzyme in a buffer solution. The developed biocatalyst, 'Glucoamylase on Sibunit' was found to have high operational stability during the continuous hydrolysis of 30-35 wt/vol % dextrin at 60 degrees C, its inactivation half-time (t1/2) exceeding 350 h. To improve the starch saccharification productivity, an immersed vortex reactor (IVR) was designed and tested in the heterogeneous process with the biocatalyst 'Glucoamylase on Sibunit'. The dextrin hydrolysis rate, as well as the process productivity in the vortex reactor, was found to increase by a factor of 1.2-1.5 in comparison with the packed-bed reactor.     

Influence of [S, S]-EDDS on phytoextraction of copper and zinc by Elsholtzia splendens from metal-contaminated soil

Two pot experiments were conducted to investigate the time course effects of the (S, S)-N, N'-ethylenediamine disuccinic acid (EDDS) addition to contaminated soil on the uptake of Cu and Zn by the Cu accumulator Elsholtzia splendens and on plant Cu and Zn concentrations at different growth stages. EDDS increased the amounts of Cu and Zn soluble in the soil, taken up by plants, concentrated in the xylem sap, and translocated from roots to stems and leaves. The increase in soil-soluble metals, especially Cu, resulted in a corresponding increase in metal concentrations in the xylem sap and leaves. The addition of EDDS to the soil increased plant Cu and Zn concentrations, especially in the leaves, and changed the proportions of Cu and Zn taken up by different plant parts. The proportions of Cu and Zn taken up by the roots were higher than by the leaves of control plants, but EDDS-treated plants showed the opposite trend. EDDS exerted greater effects at the end of the vegetative growth stage than at the start of the flowering or reproductive stages.     

The extraction by soil and absorption by plants of applied zinc and cadmium

In five consecutive years lettuce, spinach, spring wheat, endive and maize were grown in pots and the effects of native and soil-applied Zn and Cd on plant Zn and Cd concentrations were studied. The normal interactive pattern was antagonistic, Zn reducing plant Cd uptake, and conversely, but less so. Only in loam soil Zn and Cd were synergistic to some extent, plant Zn uptake increasing with applied Cd.When relating total soil Cd/Zn to plant Cd/Zn separate sets of data could be distinguished for loam and sandy soil, each fitting a straight line. The use of 0.1 M CaCl₂ instead of total extractable soil Cd/Zn makes the two sets of data to coalesce around a single straight line. All crops were found to show a positive linear relationship between 0.1 M CaCl₂-extractable soil Cd/Zn and plant Cd/Zn.     

Effect of bicarbonate and root zone temperature on uptake of Zn,Fe, Mn and Cu by different rice cultivars (Oryza sativa L.) grown in calcareous soil

Pot experiments were conducted with a calcareous soil (Inceptisol) to elucidate the effects of bicarbonate (0 and 20 mM) and root zone temperature (15° and 25°C) on the uptake of Zn, Fe, Mn and Cu by "Zn-efficient" and "Zn-inefficient" rice cultivars. Bicarbonate decreased concentrations and total uptake of Zn in shoots of "Zn-inefficient" cultivars, especially of IR 26 at 25°C, but not in Zn-efficient cultivars. Bicarbonate decreased concentrations and uptake of Fe in shoots of Zn inefficient cultivars, particularly in IR 26. Concentrations and total uptake of Mn were lower in bicarbonate treatment in the Zn-inefficient cultivars at 15°C, and in all cultivars at 25°C. However, concentration and uptake of Cu were not affected by bicarbonate in all cultivars. Compared to the 25°C root zone temperature, the concentrations and total uptake of both Zn and Cu in shoots at 15°C were lower in Zn-inefficient than in the Zn-efficient cultivars. The results indicate that Zn-efficiency in rice is causally related to high tolerance of plant to elavated bicarbonate concentrations in soil solution.     

Phytoextraction of zinc, copper, nickel and lead from a contaminated soil by different species of Brassica

In a pot culture experiment, five different species of Brassica (Brassica juncea, Brassica campestris, Brassica carinata, Brassica napus, and Brassica nigra) were grown for screening possible accumulators of heavy metals, viz. Zn, Cu, Ni, and Pb. The plants were grown to maturity in a soil irrigated with sewage effluents for more than two decades in West Delhi, India. The soil analysis showed enhanced accumulation of Zn, Cu, Ni, and Pb in this sewage-irrigated soil. Among all species, B. carinata showed the highest concentration (mg kg(-1)) as well as uptake (microg pot(-1)) of Ni and Pb at maturity. Although B. campestris showed a higher concentration of Zn in its shoots (stem plus leaf), B. carinata extracted the largest amount of this metal due to greater biomass production. However, B. juncea phytoextracted the largest amount of Cu from the soil. In general, the highest concentration and uptake of metal was observed in shoots compared to roots or seeds of the different species. Among the Brassica spp., B. carinata cv. DLSC1 emerged as the most promising, showing greater uptake of Zn, Ni, and Pb, while B. juncea cv. Pusa Bold showed the highest uptake of Cu. The B. napus also showed promise, as it ranked second with respect to total uptake of Pb, Zn, and Ni, and third for Cu. Total uptake of metals by Brassica spp. correlated negatively with available as well as the total soil metal concentrations. Among the root parameters, root length emerged as the powerful parameter to dictate the uptake of metals by Brassica spp. Probably for the first time, B. carinata was reported as a promising phytoextractor for Zn, Ni, and Pb, which performed better than B. juncea.     

Growth of arbuscular mycorrhizal mycelium in calcareous dune sand and its interaction with other soil microorganisms as estimated by measurement of specific fatty acids

Fatty acid analysis was used for determining the extent of the development of the external mycelium of AM fungi (mixed inoculum from a sand dune) growing from roots of Festuca rubra and Plantago lanceolata in calcareous dune sand. The plants were raised in chambers specially designed to permit the growth of AM mycelium in root-free compartments. In two separate experiments, growth of external mycelium in the root-free compartments was detected and the amount of mycelium was estimated using the indicator of AM fungal biomass, phospholipid fatty acid (PLFA) 16:15. The results showed that the PLFA 16:15 was suitable for estimating the mycelium emerging from the mixed inoculum obtained from the field roots of F. rubra and P. lanceolata.The PLFA 16:15 showed external mycelium to become established in the root-free compartments within a period of 3 weeks and the amount of mycelium to continue to increase at 6 and 9 weeks. Increases in neutral lipid fatty acid (NLFA) 16:15 (indicator of storage lipids) over time were inconsistent between the two experiments, but appeared to follow patterns of sporulation in each experiment.In both experiments, the root-free compartment was colonised by saprophytic fungi to a greater extent in the case of non-mycorrhizal than of AM treatment, as indicated by an increase in PLFA 18:26,9 (indicator of saprophytic fungi). The absence of an increase in the case of AM treatment indicates that AM fungal mycelium can negatively affect the growth of saprophytic fungi in this soil type. This result was, however, only weakly supported by measurements of ergosterol content. The analysis of bacteria specific PLFAs showed that bacterial biomass was not affected by the AM mycelium.     

The survival of mouse oocytes shows little or no correlation with the vitrification or freezing of the external medium,but the ability of the medium to vitrify is affected by its solute concentration and by the cooling rate

As survival of mouse oocytes subjected to vitrification depends far more on the warming rate than on the cooling rate, we wished to determine whether the lack of correlation between survival and cooling rate was mirrored by a lack of correlation between cooling rate and vitrification of the medium (EAFS), and between survival and the vitrification of the medium. The morphological and functional survival of the oocytes showed little or no relation to whether or not the EAFS medium vitrified or froze. We studied if the droplet size and the elapsed time (between placing the droplet on the Cryotop and the start of cooling) affects the result through modification of the cooling rate and solute concentration. Dehydration was rapid; consequently, the time between the placing the droplets into a Cryotop and cooling must be held to a minimum. The size of the EAFS droplet that is being cooled does not seem to affect vitrification. Finally, the degree to which samples of EAFS vitrify is firmly dependent on both its solute concentration and the cooling rate.     

The relationship between the binding to and permeabilization of phospholipid bilayer membranes by GS14dK4, a designed analog of the antimicrobial peptide gramicidin S

The cationic β-sheet cyclic tetradecapeptide cyclo[VKLdKVdYPLKVKLdYP] (GS14dK₄) is a diastereomeric lysine ring-size analog of the potent naturally occurring antimicrobial peptide gramicidin S (GS) which exhibits enhanced antimicrobial but markedly reduced hemolytic activity compared to GS itself. We have previously studied the binding of GS14dK₄ to various phospholipid bilayer model membranes using isothermal titration calorimetry [Abraham, T. et al. (2005) Biochemistry 44, 2103-2112]. In the present study, we compare the ability of GS14dK₄ to bind to and disrupt these same phospholipid model membranes by employing a fluorescent dye leakage assay to determine the ability of this peptide to permeabilize large unilamellar vesicles. We find that in general, the ability of GS14dK₄ to bind to and to permeabilize phospholipid bilayers of different compositions are not well correlated. In particular, the binding affinity of GS14dK₄ varies markedly with the charge and to some extent with the polar headgroup structure of the phospholipid and with the cholesterol content of the model membrane. Specifically, this peptide binds much more tightly to anionic than to zwitterionic phospholipids and much less tightly to cholesterol-containing than to cholesterol-free model membranes. In addition, the maximum extent of binding of GS14dK₄ can also vary considerably with phospholipid composition in a parallel fashion. In contrast, the ability of this peptide to permeabilize phospholipid vesicles is only weakly dependent on phospholipid charge, polar headgroup structure or cholesterol content. We provide tentative explanations for the observed lack of a correlation between the affinity and extent of GS14dK₄ binding to, and degree of disruption of the structure and integrity of, phospholipid bilayers membranes. We also present evidence that the lack of correlation between these two parameters may be a general phenomenon among antimicrobial peptides. Finally, we demonstrate that the affinity of binding of GS14dK4 to various phospholipid bilayer membranes is much more strongly correlated with the antimicrobial and hemolytic activities of this peptide than with its effect on the rate and extent of dye leakage in these model membrane systems.