Influence of humic substances on bioavailability of Cu and Zn during sewage sludge composting

Influence of humic substances (HS) on bioavailability of Cu and Zn was characterized during 120 days co-composting of sewage sludge and maize straw. At the initial stage of composting, Cu and Zn in sewage sludge were released as organic matter was degraded, and water soluble Cu and Zn increased markedly. Water soluble Cu and FA content decreased after 21 days whereas water soluble Zn increased during the whole process. Both HA-Cu and HA-Zn were significantly and positively correlated with HA and H/F, respectively. At the end of composting, the distribution coefficients of HA-Cu and HA-Zn reached 27.50% and 3.33% respectively with HA-Cu/HA-Zn ratio increased from 1.29 to 2.73. The results suggest that Cu combined with HA more strongly than Zn, and composting treatment could decrease bioavailability of Cu markedly.     

Hemicellulosic polymers of cabbage leaves

The hemicellulosic polymers of depectinated cell-wall material of immature cabbage leaves have been extracted by alkali, fractionated by ion-exchange chromatography and their structural features studied. In the 1 M potassium hydroxide-soluble fraction the main polymers are arabinoxylan-xyloglucan-pectic, arabinoxylan-pectic-protein and arabinoxylan-xyloglucan-pectic-protein complexes. Small amounts of polysaccharide-protein-polyphenol complexes are also present. In the 4 M potassium hydroxide-soluble fraction the predominant polymers are two xyloglucans, the major one of which appears to have ca 10% of(1 → 4)-linked and 3% of(1 → 4,6)-linked mannose residues associated with it, and both have terminal galactose, fucose and possibly arabinose residues in the side chains. Methylation analysis of the oligosaccharides, formed by degradation with cellulase, and partial hydrolysis of the methylated xyloglucan, followed by re-methylation with CD₃I, have enabled the formulation of a tentative structure which is similar to other plant galactoxyloglucans. It was not possible to establish whether the mannose residues are part of an associated glucomannan or whether they are an integral part of the glucan backbone. The general structural features of the hemicellulosic polymers are discussed in the light of these results.     

The hydrogeology of a catchment area and an artificially divided dystrophic lake — consequences for the limnology of Lake Fuchskuhle

The hydrogeology between the catchment area and the divided dystrophic Lake Fuchskuhle with respect to the genesis and the land-water interactions were investigated. Water levels at numerous locations in the catchment area were measured in order to characterize the hydrology. The water balance of the area was calculated based on long term climatic investigations. The geology of the peat was documented at 25 sampling points by cores collected with a peat drill. Chemical parameters including pH, total phosphorus and total nitrogen concentrations, DOC concentration, colour (SAK 436 m^–1) and the UV₂₅₄/DOC ratio in the catchment area and in two compartments (NE and SW compartment) were determined. The chemical fluxes of DOC, nitrogen and phosphorus from the catchment area into one compartment (SW compartment) were determined. During the genesis of the Lake Fuchskuhle area two aquifer systems (local peat aquifer, regional sandy main aquifer) developed. Both aquifers are largely independently with almost no lateral interactions. Two compartments are supplied with water from the local peat aquifer. From the other two compartments, however, water is flowing out into the peat body. During high groundwater inflow into the SW compartment higher concentration of DOC, nitrogen and phosphorus in the SW compartment were detected. The fen can be divided in two parts: in the meso — to eutrophic fen northwest and the mainly meso — to oligotrophic — acid fen in the southeast. The significant differences in parameters such as pH, conductivity and DOC concentration gave a clear picture of the heterogeneity of the two compartments and their dependence on the catchment area with the two aquifers.     

Silicon-mediated alleviation of Mn toxicity in Cucumis sativus in relation to activities of superoxide dismutase and ascorbate peroxidase

The effects of exogenous silicon (Si) on plant growth, activities of superoxide dismutase (SOD), guaiacol peroxidase (GPX), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), glutathione reductase (GR) and catalase, and concentrations of ascorbate and glutathione were investigated in cucumber (Cucumis sativus L.) plants treated with excess manganese (Mn) (600 microM). Compared with the treatment of normal Mn (10 microM), excess Mn significantly increased H2O2 concentration and lipid peroxidation indicated by accumulation of thiobarbituric acid reactive substances. The leaves showed apparent symptoms of Mn toxicity and the plant growth was significantly inhibited by excess Mn. The addition of Si significantly decreased lipid peroxidation caused by excess Mn, inhibited the appearance of Mn toxicity symptoms, and improved plant growth. This alleviation of Mn toxicity by Si was related to a significant increase in the activities of SOD, APX, DHAR and GR and the concentrations of ascorbate and glutathione.     

Substances isolated from Mandragora species

The present state of knowledge in the chemistry of mandragora plant is reviewed. Isolations and identifications of the compounds were done from all parts of this plant. Up-to-date more than 80 substances were identified in different species of the genus Mandragora.     

Production of antimicrobial substances by Bacillus subtilis LFE-1, B. firmus HO-1 and B. licheniformis T6-5 isolated from an oil reservoir in Brazil

AIMS: Forty Bacillus strains isolated from a Brazilian oil reservoir were tested against each other to select strains producing antimicrobial substances (AMS). Three strains, Bacillus subtilis (LFE-1), Bacillus firmus (H2O-1) and Bacillus licheniformis (T6-5), were selected due to their ability to inhibit more than 65% of the Bacillus strains tested. These three strains were also investigated for their capability to inhibit sulphate-reducing bacteria (SRB). Furthermore, physiological and biochemical characteristics of the antimicrobial compounds produced by the selected strains were determined. METHODS AND RESULTS: Among the forty strains tested, 36 (90%) strains were able to inhibit at least one Bacillus strain used as indicator in plate assays and three of them (LFE-1, T6-5 and H2O-1) were able to inhibit 65, 70 and 97.5% of the 40 strains studied here respectively. Clear zones of inhibition were observed when H2O-1 was tested against SRB-containing consortium T6-lab and Desulfovibrio alaskensis strain NCIMB 13491, while strain T6-5 was able to inhibit only the D. alaskensis strain. The three substances showed to be insensitive to different enzymes and chemicals, were heat stable and the substances produced by strains T6-5 and H2O-1 were active over a wide pH range. CONCLUSIONS: Three different AMS produced by Bacillus strains from an oil reservoir, two of them with activity against SRB, are presented here. SIGNIFICANCE AND IMPACT OF THE STUDY: The preliminary characterization of these AMS points to their potential use as biocides in the petroleum industry for controlling problems associated with SRB.     

Possible mechanisms underlying copper-induced damage in biological membranes leading to cellular toxicity

It is generally accepted that copper toxicity is a consequence of the generation of reactive oxygen species (ROS) by copper ions via Fenton or Haber-Weiss reactions. Copper ions display high affinity for thiol and amino groups occurring in proteins. Thus, specialized proteins containing clusters of these groups transport and store copper ions, hampering their potential toxicity. This mechanism, however, may be overwhelmed under copper overloading conditions, in which copper ions may bind to thiol groups occurring in proteins non-related to copper metabolism. In this study, we propose that indiscriminate copper binding may lead to damaging consequences to protein structure, modifying their biological functions. Therefore, we treated liver subcellular membrane fractions, including microsomes, with Cu²⁺ ions either alone or in the presence of ascorbate (Cu²⁺/ascorbate); we then assayed both copper-binding to membranes, and microsomal cytochrome P450 oxidative system and GSH-transferase activities. All assayed sub-cellular membrane fractions treated with Cu²⁺ alone displayed Cu²⁺-binding, which was significantly increased in the presence of Zn²⁺, Hg²⁺, Cd²⁺, Ag⁺¹ and As³⁺. Treatment of microsomes with Cu²⁺ in the μM range decreased the microsomal thiol content; in the presence of ascorbate, Cu²⁺ added in the nM concentrations range induced a significant microsomal lipoperoxidation; noteworthy, increasing Cu²⁺ concentration to ≥50 μM led to non-detectable lipoperoxidation levels. On the other hand, μM Cu²⁺ led to the inhibition of the enzymatic activities tested to the same extent in either presence or absence of ascorbate. We discuss the possible significance of indiscriminate copper binding to thiol proteins as a possible mechanism underlying copper-induced toxicity.     

General Description of Partly Meromictic Hypertrophic Lake Verevi,its Ecological Status,Changes during the Past Eight Decades,and Restoration Problems

The present study describes generally the ecosystem of Lake Verevi while more detailed approaches are presented in the same issue. The main task of the article is to estimate long-term changes and find the best method for the restoration of good ecological status. Lake Verevi (surface 12.6 ha, mean depth 3.6 m, maximum depth 11 m, drainage area 1.1 km², water exchange 0.63-times per year) is a hypertrophic hard-water lake located in town Elva (6400 inhabitants). Long-term complex limnological investigations have taken place since 1929. The lake has been contaminated by irregular discharge of urban wastewaters from oxidation ponds since 1978, flood from streets, and infiltrated waters from the surrounding farms. The so-called spring meromixis occurred due to extremely warm springs in recent years. The index value of buffer capacity of Lake Verevi calculated from natural conditions is on the medium level. Water properties were analysed according to the requirements of the EU Water Framework Directive. According to the classification, water quality as a long-term average of surface layers is moderate-good, but the water quality of bottom layers is bad. Values in deeper layers usually exceed 20–30 times the calculated reference values by Vighi and Chiaudani’s model. Naturally, at the beginning of the 20th century the limnological type of the lake was moderately eutrophic. During the 1980s and 1990s the ecosystem was out of balance by abiotic characteristics as well as by plankton indicators. Rapid fluctuations of species composition and abundance can be found in recent years. Seasonal variations are considerable and species composition differs remarkably also in the water column. The dominating macrophyte species vary from year to year. Since the annual amount of precipitation from the atmosphere onto the lake surface is several times higher, the impact of swimmers could be considered irrelevant. Some restoration methods were discussed. The first step, stopping external pollution, was completed by damming the inlet. Drainage (siphoning) of the hypolimnetic water is discussed. Secondary pollution occurs because Fe:P values are below the threshold. The authors propose to use phosphorus precipitation and hypolimnetic aeration instead of siphoning.     

Seasonal modulation of free radical metabolism in estivating land snails Helix aspersa

We investigated the regulation of free radical metabolism in Helix aspersa snails during a cycle of 20-day estivation and 24-h arousal in summer in comparison with estivation/arousal in winter-snails. In winter-snails (J. Exp. Biol. 206, 675-685, 2003), we had already observed an increase in the selenium-dependent glutathione-peroxidase (Se-GPX) activity in foot muscle and hepatopancreas and in the contents of hepatopancreas GSH-equivalents (GSH-eq=GSH+2 GSSG) during estivation compared with 24-h aroused snails. Summer-estivation prompted a 3.6-fold increase in Se-GPX activity in hepatopancreas, though not in foot muscle. Total-superoxide dismutase and catalase activities in hepatopancreas decreased (by 30-40%) during summer-estivation; however, no changes occurred in the activities of glutathione reductase, glutathione S-transferase and glucose-6-phosphate dehydrogenase in the two organs. GSH-eq levels were increased (by 54%) in foot muscle during estivation, but were unchanged in hepatopancreas. In contrast with winter-snails, oxidative stress markers (lipid peroxidation, carbonyl protein, and the GSSG/GSH-eq ratio) were unaltered during estivation/arousal in summer. These results demonstrate that seasonality modulates not only the absolute activities/levels of antioxidants (enzymes and GSH-eq) in H. aspersa, but also the regulatory process that controls the snail's antioxidant capacity during estivation/arousal. These results suggest that H. aspersa has an "internal clock" controlling the regulation of free radical metabolism in the different seasons.     

D-VITAMINS AND THEIR PRECURSORS AS GROWTH REGULATORS IN AXENICALLY CULTIVATED MARINE MACROALGAE1

Light petroleum extracts from thalli of Fucus vesiculosus (L.) and Laminaria digitata (Huds.) Lamour. stimulate growth of axenically cultured Fucus spiralis L. and Enteromorpha compressa (L.) Grev. in amounts per litre culture medium corresponding to one to 10 mg wet weight of the brown algae. This indicates the presence of a lipophilic, very active growth regulator in the blades. Extracts from the meristematic zone of Laminaria are much less active. Vitamins D₃, D₂ and 1,25-(OH)₂-D₃ at 1·10^?8– 1·10^?7 M increase the fresh weight of Enteromorpha compressa and Fucus spiralis up to 100% or more. The dry weight of Nemalion helminthoides (Veil, in With.) Batt. is also increased under the same conditions. Ergosterol and cholesterol are also growth-stimulating but higher concentrations (e.g. 1·10^?6 M) are necessary. The effects of the D vitamins manifest themselves without any auxins being added to the medium.