Changes in the origin and quality of soil organic matter after pasture introduction in Rondônia (Brazil)

We examined the effects of the conversion of tropical forest to pasture on soil organic matter (SOM) origin and quality along a chronosequence of sites, including a primary forest and six pastures. Bulk soil samples received a physical size-fractionation treatment to assess the contribution of each compartment to total SOM pool. Besides a general increase in total C and N stocks along the chronosequence, we observed a reduction of the relative contribution of the coarser fractions to total soil C content, and an increased concentration in the finer fractions. The origin of the C in each size fraction was established from measurements of¹³C abundance. After 80 years about 93% of the C in the least humified fraction of the top 10 cm of soil was of pasture origin, while in the most humified it was 82%. Chemical analyses indicated that the fine silt and coarse clay fractions contained the most refractory carbon.     

Determination of substrate utilization patterns of soil microbial communities: An approach to assess population changes after hydrocarbon pollution

Abstract: Changes in hydrocarbon content in soils resulted in characteristic shifts of the substrate utilization patterns as tested with the Biolog system. The altered patterns of substrate utilization corresponded to similar changes in abundance of hydrocarbon-utilizing bacteria and the occurrence of specific bacterial groups in the soils. Substrate utilization patterns as recorded with the Biolog system are suitable for rapidly assessing dynamics of autochthonous soil communities and evaluating their biodegradative potential.     

Effects of manipulation of food supply on estuarine meiobenthos

A comparative mesocosm experiment was carried out to determine the effects of natural foods of different quality and quantity on the structure of natural meiobenthic communities collected in undisturbed sediment from the polluted Westerschelde and the comparatively undisturbed Gironde estuaries. Nematode communities are more diverse and species rich in the latter estuary. The organic matter or foods used were phytoplankton, green alga, salt marsh plant detritus and leaf litter detritus which were added at three dose rates including a high dose. There was no change in community structure in response to the treatments in either of the estuarine meiobenthic communities. Analysis of all the results from this experiment indicate that the food quantity manipulations had almost no effect on the deposit feeding meiofauna. It may be that the reserves of organic matter within the sediment were sufficient to satisfy their dietary requirements for the duration of the experiment. The abundance of diatom/epigrowth feeding nematodes which were initially dominant in the Gironde, declined substantially suggesting that they may have been food limited since diatoms were not among the sources of organic matter added to the mesocosm. There was no specific response to the five different types of organic matter added to the mesocosm     

Are polyphosphates or phosphate esters prebiotic reagents?

It is widely held that there was a phosphate compound in prebiotic chemistry that played the role of adenosine triphosphate and that the first living organisms had ribose-phosphate in the backbone of their genetic material. However, there are no known efficient prebiotic synthesis of high-energy phosphates or phosphate esters. We review the occurrence of phosphates in Nature, the efficiency of the volcanic synthesis of P₄O₁₀, the efficiency of polyphosphate synthesis by heating phosphate minerals under geological conditions, and the use of high-energy organic compounds such as cyanamide or hydrogen cyanide. These are shown to be inefficient processes especially when the hydrolysis of the polyphosphates is taken into account. For example, if a whole atmosphere of methane or carbon monoxide were converted to cyanide which somehow synthesized polyphosphates quantitatively, the polyphosphate concentration in the ocean would still have been insignificant. We also attempted to find more efficient high-energy polymerizing agents by spark discharge syntheses, but without success. There may still be undiscovered robust prebiotic syntheses of polyphosphates, or mechanisms for concentrating them, but we conclude that phosphate esters may not have been constituents of the first genetic material. Phosphoanhydrides are also unlikely as prebiotic energy sources. Correspondence to: S.L. Miller     

The oxidation of chiral alcohols catalyzed by catalase in organic solvents

The catalytic properties of bovine liver catalase have been investigated in organic solvents. In tetrahydrofuran, dioxane, and acetone (all containing 1% to 3% of water), the enzyme breaks down tert-butyl hydroperoxide several fold faster than in pure water. Furthermore, the rate of catalase-catalyzed production of tert-butanol from tert-butyl hydroperoxide increases more than 400-fold upon transition from aqueous buffer to ethanol as the reaction medium. The mechanistic rationale for this striking effect is that in aqueous buffer the rate-limiting step of the enzymatic process involves the reduction of catalase's compound I by tert-butyl hydroperoxide. In ethanol, and additional step in the reaction scheme becomes available in which ethanol, greatly outcompeting the hydroperoxide, is oxidized by compound I regenerating the free enzyme. In solvents, such as acetonitrile or tetrahydrofuran, which themselves are not oxidizable by compound I, catalase catalyzes the oxidation of numerous primary and secondary alcohols with tert-butyl hydroperoxide to the corresponding aldehydes or ketones. The enzymatic oxidation of some chiral alcohols (2,3-butanediol, citronellol, and menthol) under these conditions occurs enantioselectively. Examination of the enantioselectivity for the oxidation of 2,3-butanediol in a series of organic solvents reveals a considerable solvent dependence. (c) 1995 John Wiley & Sons, Inc.     

The effective diffusion coefficient and the distribution constant for small molecules in calcium-alginate gel beads

The effective diffusion coefficient, D(e), and the distribution constant, K(i), for selected mono- and disaccharides and organic acids were determined in homogeneous calcium-alginate gel with and without entrapped bacteria. Results were obtained from transient concentration changes in well-stirred solutions of limited volume, in which the gel beads were suspended. The effective diffusioncoefficients and the distribution constants were estimated by fitting mathematical model predictions to the experimental data using a nonlinear model fitting program (MODFIT). Both single solute diffusion and multiple solute diffusion were performed. A small positive effect was obtained onthe values of D(e) for the system of multiple solute diffusion; however, the values of K(i) were not significantly influenced. For the nine solutes tested, D(e) for 2% Ca-alginate gel beads was found to be approximately 85% of the diffusivity measured in water. The effects on D(e) and K(i), for lactose and lactic acid were determined for variations of alginate concentration, pH, temperature, and biomass content in the beads. D(e) decreased linearly for both lactose and lactic acid with increasing cell concentration in the Ca-alginate gel. K(i), was constant for both lactose and lactic acid with increasing cell concentration. D(e) was significantly lower at pH 4.5 than at pH 5.5 and 6.5 for both lactose and lactic acid. Furthermore, D(e) seemed to decrease with increased alginate concentration in the range of 1% to 4%. The diffusion rate increased with increasing temperature, and the activation energy for the diffusion process for both lactose and lactic acid was constant in the temperature range tested. (c) 1995 John Wiley & Sons Inc.     

Polyphenoloxidases immobilized in organic gels: Properties and applications in the detoxification of aromatic compounds

Gelatine gels originate from water in oil microemulsions in which the ternary system consists of isooctane/ sulfosuccinic acid bis [2-ethyl hexyl] ester/water; the solubilization of gelatin in the water pool of these microemulsions transforms them into viscous gels in which it is possible to cosolubilize various reactive molecules. These gels were used to immobilize two phenoloxidases, a laccase from Trametes versicolor and a tyrosinase from mushroom. The best balance between gel retention and catalytic activity was reached at a gelatine concentration of 2.5% (w/v) in the case of tyrosinase, while laccase immobilization was independent of gelatine concentration. Both enzymes kept the same optimum pH as the corresponding soluble controls, while a partial loss of activity was observed when they were immobilized. Immobilized enzymes showed an increased stability when incubated for several days at 4 degrees C with a very low release from the gels in the incubation solutions. The immobilization of tyrosinase and of laccase enhanced stability to thermal inactivation. Furthermore, gel-entrapped tyrosinase was almost completely preserved from proteolysis: more than 80% of the activity was maintained, while only 25% of the soluble control activity was detected after the same proteolytic treatments. A column packed with gel-immobilized tyrosinase was used to demonstrate that enzymes immobilized with this technique may be reused several times in the same reaction without loosing their efficiency. Finally, gel-entrapped tyrosinase and laccase were capable of removing naturally occurring and xeno-biotic aromatic compounds from aqueous suspensions with different degrees of efficiency. (c) 1995 John Wiley & Sons, Inc.     

Vanadium derivatives act as growth factor — mimetic compounds upon differentiation and proliferation of osteoblast-like UMR106 cells

The effect of different vanadium compounds on proliferation and differentiation was examined in osteoblast-like UMR106 cells. Vanadate increased the cell growth in a biphasic manner, the higher doses inhibiting cell progression. Vanadyl stimulated cell proliferation in a dose-responsive manner. Similar to vanadate, pervanadate increased osteoblast-like cell proliferation in a biphasic manner but no inhibition of growth was observed. Vanadyl and pervanadate were stronger stimulators of cell growth than vanadate. Only vanadate was able to regulate the cell differentiation as measured by cell alkaline phosphatase activity. These results suggest that vanadium derivatives behave like growth factors on osteoblast-like cells and are potential pharmacological tools in the control of cell growth.     

Culturing the fairy shrimp Streptocephalus dichotomus Baird using livestock waste – a reclamation study

The present study describes a defined culturetechnique for the fairy shrimp, Streptocephalusdichotomus. It emphasizes reclamation of low-cost organiclive-stock waste(cow-dung), lime powder, and urea. These compounds wereused to enrich algal and diatom populations in themedium. These algae and diatoms were fed to filter feedingfairy shrimps to yield anostracanbiomass. A production of 262 ± 6 animals l^–1was obtained in an experimental tank compared to 36 ± 4animals l^–1 in the controls. Interestingly,the total number of clutches in experimentalfemales (12 ± 2), relative to the control (7 ± 1),increased too.     

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.