A toxicity view of the pesticide picloram when immobilized onto a silica gel surface

The pesticide picloram (4-amino-3,5,6-trichloropicolinic acid) was anchored onto silica gel to yield a new surface. Isothermal microcalorimetry was applied to study the toxic effects caused to microbial activity of a typical Brazilian agricultural soil by application of free and immobilized picloram. The activity of the microorganisms in 1.50 g of soil sample was stimulated by addition of 6.0 mg of glucose plus 6.0 mg of ammonium sulfate under 34.8% controlled humidity at 298.15±0.02 K. The activity was recorded through power–time curves for increasing amounts of the active principle, varying from zero to 10.00 g g^–1. The increasing amounts of picloram, either free or immobilized, caused a decrease of the original thermal effect. The calorimetric data showed that the anchored pesticide presented a much lower toxic effect than the free picloram on the microbial activity.     

Effect of Lead Contamination on Soil Microbial Activity Measured by Microcalorimetry

Microcalorimetry was used to investigate the microbial activity in three types of soil (orchard soil, crop soil, forest soil) in Wuhan, China, and to evaluate the influence of different concentrations of lead (Pb²⁺) on soil microbial activity. The experimental results revealed that due to different physical and chemical characteristics of the soils, soil microbial activity in three soil samples were in a descending sequence: orchards soil, crops soil, forest soil. Six levels of Pb viz. 0, 10, 20, 40, 80, 160 μg·g⁻¹ were applied in these soils, and the results showed that an increase of the amount of Pb²⁺ is associated with a decrease in microbial activity in the soils due to the toxic effect of Pb²⁺. In order to gain further insight of the sequential change of microorganisms, determination of colony forming units (CFU) was performed to provide a negative linear correlation between the heat effect and the respective number of microorganisms in the system.     

Study of the influence of different forest species on the microbial activity in soils

Microcalorimetry was used to study the seasonal evolution over one year of the microbial activity in a humic-eutrophic Cambisol soil as a function of its forest cover. The study was carried out on three soils with identical origin but covered with different forest species: pine, eucalyptus, and a typical Atlantic-humid riverside forest. Some other physical, chemical and biological properties and environmental parameters, mainly humidity and environmental temperature, were considered to analyze their influence on soil microbial activity. The study was performed using a microcalorimeter Thermal Analysis Monitor 2277 in which the experiments were carried out with 1 g soil samples treated with 1.25 mg glucose g^–1 soil. From the measured results it follows that pine forest soil is the least productive of the three, as it generates an average heat of 2.7 vs. 5.9 J g^–1 generated by the eucalyptus forest soil and 3.1 J g^–1 generated by the riverside forest soil. These results are dependent on the remaining physical, chemical and biological features analysed and because of this, pine forest soil, with a pH value 3.3 in spring, shows a small capacity to maintain a stable microbial population which is the lowest of the three (0.079·10⁸ to 0.46·10⁸ microorganisms g^–1 soil) while riverside soil microbial population is in the range from 7.9·10⁸ to 17·10⁸ microorganisms g^–1 soil.     

Development of an experimental procedure to analyse the ‘soil health state’ by microcalorimetry

This work is a ‘historical’revision of the evolution of an experimental procedure developed by Prof.Lisardo Núñez and his research group TERBIPROMAT to study thesustainability and the soil health state.From the very beginning,in 1993, the microbial activity was the main bioindicator selected to analysethe ‘soil health state’. For this reason, a microcalorimetrictechnique was used lately to analyse the influence of different human activitiessuch as reforestations, agricultural exploitation or pollution on the microbialactivity in different soils. Microcalorimetry is the main scientific techniqueused in this research to follow the stimulation of the microbial activityby addition of glucose. The data obtained were complemented by a study ofphysical, chemical and biological parameters of soil and allowed to followthe microbial activity in soils of Galicia (Spain) along the year.The final results, still in revision, will be helpful in establishinga data basis for real maps of the ‘health state’ of differentsoils. Such maps could be used to design processes that help us to decidehow we should exploit soils ensuring their sustainability.     

Effect of storage of soil at 4°C on the microbial activity studied by microcalorimetry

The effect of the storage of soils on their microbial activity has been studied using a microcalorimetric method. Soil samples were kept in closed polyethene bags at 4°C during 3–6 months. Results show changes in the slope of the differentP?t curves recorded from the samples stored at 4°C. This fact strongly suggest the existence of changes of the microbial activity of soil as the heat evolution is a direct measurement of the cells metabolic activity. The value of the Peak-time (time in which the microcalorimetric signal reaches the maximum value) is related with the microbial density of soil samples. This parameter was affected by the time of storage increasing with time. The total heat evolutionQ(t), of the soil samples amended with glucose calculated from the area limited by the Power-Time curves, also decreases with the time of storage. The soil that had been stored for 6 months before experiments, showed the lowest valu ofQ(t).     

The effect of solid-liquid effluents from anaerobic digesters on soilmicrobial activity

A calorimetric procedure is developed to study the effect on the soil of the effluents resulting for the anaerobic digestion of slaughtering houses residues. DSC was used to study the pyrolysis properties of the effluent and the soil while isothermal calorimetry is applied to study the microbial activity in the effluent and to assess on its effect on the microbial activity of the soil where the industrial digester will be situated. The calorimetric data were studied together with the chemical and biological properties of that residue. Results showed that effluent is constituted by low levels of carbon and high levels of nitrogen. The power-time curves of the effluent have the typical shape of microbial growth yielding microbial growth rate constants between 0.37 and 0.53 h⁻¹ for about 4 and 11 h. The addition of the effluent to the soil decreases the heat of pyrolysis with time and stimulates the heat flow rate of the microbial metabolism.     

Characterization of River Natural Organic Matter by High-Performance Size Exclusion Chromatography

The molecular weight of natural organic matter from the Yeongsan and Seomjin Rivers and the discharge from the wastewater treatment plants were analyzed for seasonal characteristics by high-performance size exclusion chromatography. The distribution of molecular weights demonstrated relationships with microbial activity and seasonal variations with temperature. Dissolved organic carbon and total organic carbon for the Seomjin River were from 1.6 to 3.1 mg L^?1; for the Yeongsan River system, these parameters were between 2.0 and 8.0 mg L^?1. There were no significant differences between upstream and downstream organic matter. The biochemical oxygen demand (0.8–2.5 mg L^?1) for the Seomjin River was less than the chemical oxygen demand (2.9–5.0 mg L^?1). Similarly, the biochemical oxygen demand (0.9–4.6 mg L^?1) for the Yeongsan River was lower than the chemical oxygen demand (3.8–10.6 mg L^?1). The molecular weight of aromatic compounds increased as the water temperature decreased in October, whereas the molecular weights of proteins decreased as the water temperature increased. These results suggest that as microbial activity increased, natural organic matter with a smaller molecular weight may be employed as an energy source by microorganisms. As a result, seasonal variation of the water temperature may influence the distribution of organic matter in the rivers based on molecular weight and microbial activity such that the smaller natural organic matter was more readily degraded by microorganisms.     

Studying the toxic effect of cadmium and hexavalent chromium on microbial activity of a soil and pure microbe

Using TAM III multi-channel calorimetry combined with direct microorganism counting (bacteria, actinomycetes and fungi) under laboratory conditions, we determined the microbial population count, resistance and activity toward cadmium (Cd(II)) and hexavalent chromium (Cr(VI)) toxicity in soil. The thermokinetic parameters, which can represent soil microbial activity, were calculated from power-time curves of soil microbial activity obtained by microcalorimetric measurement. Simultaneous application of the two methods showed that growth rate constant (k), peak-heat output power (P _max) and the number of living microorganisms decreased with increasing concentration of Cd and Cr. The accumulation of Cr on E. coli was conducted by HPLC-ICP-MS. Cr⁶⁺ accumulation by Escherichia coli was increased steadily with increasing Cr⁶⁺ concentration. The results revealed that the change in some thermo-kinetic parameters could have good corresponding relationship with metal accumulation. Our work also suggests that microcalorimetry is a fast, simple, more sensitive, on-line and in vitro method that can be easily performed to study the toxicity of different species of heavy metals on microorganism compared to other biological methods, and can combine with other analytic methods to study the interaction mechanism between environmental toxicants and microbes.     

Theoretical Study of the Formation of Benzofurotriazines by Reaction of 3-Substituted 1,2,4-Triazines and Fused Azolo[1,2,4]triazines with Resorcinol

3-Methylthio- and 3-amino-1,2,4-triazines react with resorcinol to give benzofurotetrahydrotriazine derivatives, while reactions of [1,2,4]triazolo[4,3-b]- and tetrazolo[1,5-b][1,2,4]triazines with resorcinol stop at the stage of resorcinol addition. According to the results of quantum-chemical calculations, the possibility for further cyclization of the resorcinol addition products is determined by the following factors: tautomeric and conformational states of the compounds, which ensure spatial proximity of the hydroxy group to the cyclization center (C⁶); charges on the C⁶ atom of the triazine ring and oxygen atom of the resorcinol fragment in the conformation most favorable for cyclization; and energies of the highest occupied and lowest unoccupied molecular orbitals of the resorcinol addition products.     

The role of biodegradation during bioventing of soil contaminated with jet fuel

The enhancing rem oval of kerosene (jet fuel) from contaminated soil during bioventing resulting from biodegradation was compared to the physical removal by evaporation only on bench-scale columns at the controlled temperature of 20°C (±2.5°C). Carbon dioxide-free air and nitrogen were used as flushing gases, at the constant continuous flow rate of 1 dm³/h. Kerosene concentrations in soil up to 35000 mg/kg were not toxic for indigenous microbial population. Much slower kerosene biodegradation rates observed for soil from a contaminated site, as compared to soil artificialy contaminated with kerosene, were the result of a lower bioavailability of “aged” kerosene, and the presence of compounds that might be persistent or toxic to kerosene-specific degraders. The inhibitory effect of toluene to indigenous microorganisms was found at above 75% of the toluene saturation concentrations in the gas phase. After 29 d, the overall bioventing efficiency was 17–23%, depending on whether CO₂ production or O₂ uptake wasused for caculations, as compared to the removal of 10% when biodegradation was excluded. The increase in efficiency by 50–100% owing to biodegradation would be more spectacular at lowr kerosene concentrations during the “tailing” phase, with diffusionlimited desorption, and much lower evaporation of less volatile constituents. Limitation of bioventing as a result of low bioavailability related to intraparticle sorption of residual contamination is discussed.     

Spectrophotometric determination of catechol,epinephrine, dopa,dopamine and other aromatic vic-diols

Aromatic vic-diols such as catechols, epinephrine, norepinephrine, dopa, and dopamine can be determined spectrophotometrically by nitration with sodium nitrite in slightly acidic solution. The method is selective for aromatic vic-diols in which either the 3- or 4-position is unsubstituted and these positions are not sterically blocked. Tungstate or molybdata ions increase the color intensity, probably by stabilizing the nitrated phenol by complex formation. Molybdate is more effective than tungstate. For most diphenols the optimum pH is around 5.0–5.5 (acetate buffer) but this depends on the diphenol as well as on the particular buffer system. The optimum time for nitration (2–30 min) also depends on the diphenol. After nitration for the optimum duration, the solution is made basic; an absorption band appears at about 500 nm with a molar absorptivity of ca. 10⁴ 1 mol^-1 cm^-1. The system follows Beer's law provided that molybdate ion is present and both the pH and reaction time are optimized. The minimum detectable amount of diphenol is about 5 nmol, for an absorbance of 0.01 in a 1.00-cm cell. Phenol, hydroquinone, resorcinol, pyrogallol, phloroglucinol, guaiacol, and veratrole, do not interfere.     

Calorimetric determination of the effect of ammonium-iron(II) phosphate monohydrate on Rhodic Eutrudox Brazilian soil

The fertilizer NH₄FePO₄·H₂O (AIP) was synthesized under mild hydrothermal conditions to be applied on soils to prevent iron deficiencies. The effect of the addition of AIP on soil microbial activity was studied by calorimetry, determining both basal respiration and carbon mineralization by means of the addition of an external carbon source. Thermal analyses (TG and DSC) were also used to provide additional soil properties. The effect of different amounts of AIP on soil microbial activity was quantitatively analyzed by a mass and energy balance performed via the analysis of the power-time curves. These balances allowed determination of the impact of AIP on soil more rapidly than conventional methodologies. The increase in the amount of added AIP leads to a less efficient metabolism, probably due microbial competition for the nitrogen source provided by the AIP and for the carbon source.     

Synchronous fluorescence for simultaneous determination of hydroquinone and resorcinol in air samples

Several phenolic compounds are present in tobacco smoke. They are formed from the pyrolysis of tobacco during the smoking process and all of them are toxic. Therefore, the determination of these compounds in air samples is important. A rapid, simple, and sensitive method using a synchronous spectrofluorimetry technique was developed to quantify hydroquinone and resorcinol simultaneously. One of the advantages of this method is the simple and rapid sampling technique, which uses water as the absorption solution of the analytes in the air sample. The precision of the method (%RSD) was 1.8% and the detection limits were 0.125 mg m^–3 and 0.292 mg m^–3 for hydroquinone and resorcinol, respectively.     

Design of an experimental procedure to assess soil health state

The design of a rigorous experimental procedure is the basis for any environmental study. In this work, the basic criteria are established for determination of soil health using microcalorimetry as the main technique complemented by the study of physical (temperature, moisture, porosity, hydraulic conductivity, density and plasticity), chemical (pH and C to N ratio) and biological features (most probable number of microorganisms and organic matter content), and also environmental properties in the form of bioclimatic diagrams. The design was elaborated using as a reference a humic eutrophic-Cambisol subjected to afforestation with P. pinaster Aiton situated in Viveiro (Galicia, NW Spain). Main results of this study refer to total heat evolved during the processes (2.65 to 3.81 J g^–1), time to reach the maximum of the peak from 16.17 to 19.29 h, and microbial growth rate constant from 0.0732 to 0.1043 h^–1. These results change over the year as they are influenced by the action of environmental parameters over soil microbial activity. The results are in close agreement with some others previously reported using different experimental techniques.     

Holistic protocol for callus culture optimization using statistical modelling

Plants endue a key role against illnesses caused by oxidative stress. These attributes are frequently associated with polyphenolic compounds. However, presence and concentration of secondary metabolites are affected by abiotic factors. The in vitro culture techniques can solve these drawbacks. Peppers can be a suitable alternative to obtain polyphenols. Aiming to optimise the callus culture stage from Capsicum baccatum to produce polyphenols, this work evaluated systemically the effects of the explant’s origin (root, hypocotyl and cotyledon), growth hormone type (2,4-dichlorophenoxyacetic acid (2,4-D), benzylaminopurine (BAP) and a combination of 2,4-D/BAP at five-to-one ratio) and concentration (0.023–10.000 mg L^?1) on callus culture efficiency parameters using a multilevel factorial design. The root explant in combination with BAP at 1.138 mg L^?1 ensured the optimal values of the assessed responses; ?callus mass (225.03 mg), antioxidant activity (35.95%), total phenols (11.48 mg of GAE/g DE) and flavonoids (15.92 mg of RU/g DE) production.     

Synthesis,characterization and in vitro antimicrobial activity of some novel 5-substituted Schiff and Mannich base of isatin derivatives

With the aim of developing potential antimicrobials, a series of novel Ciprofloxacin methylene isatin derivatives incorporating different aromatic aldehydes were synthesized and characterized by FTIR, ¹H NMR, Mass spectroscopy and bases of elemental analysis. In addition, the in vitro antibacterial and antifungal properties were tested against some human pathogenic microorganisms by employing the disc diffusion technique. A majority of compounds were showing activity against several of the microorganisms. The relationship between the functional group variation and the biological activity of the evaluated compounds is discussed. From comparisons of the compounds, 3c was determined to be the most active compound.     

Interpretation of the Metabolic Enthalpy Change, ΔHmet,Calculated for Microbial Growth Reactions in Soils

The microcalorimetric method was used to calculate the metabolic enthalpy change per mol of glucose degraded by soil microorganisms, ΔH _met. This parameter has been calculated by microcalorimetry for many organic, inorganic and biochemical reactions, but there is only some information about its quantification for microbial growth reactions in soils. Values of ΔH _met were calculated for different soil samples collected in Galicia (Spain) and Campinas (Săo Paolo, Brazil). Exponential microbial growth was stimulated in all soil samples by the addition of glucose and power-time curves were recorded. Results showed changes in the values of ΔH _met calculated for all the soil samples, suggesting a dependence of this value with the microbial growth rate constant, with the percentage of growth, with the initial number of microorganisms of soil samples, with the quantity of glucose added and with the strain of bacteria growing in soil. The interpretation of variations of ΔH _met provides important qualitative and quantitative information. It reports data that allow to interpret from a qualitative point of view, the increase in biomass as a consequence of the degradation of the organic matter in soil, to understand changes in the percentages of soil organic matter and to know if the microbial population growing in differential soil samples is homogeneous. Therefore, to report that value would be very important in ecological studies, but beforehand, it is necessary to solve some problems that can appear in the experiments done to make the quantification . This revised version was published online in August 2006 with corrections to the Cover Date.     

Bioenergetics and bioremediation of contaminated soil

The microbial biodegradation of xenobiotic compounds in soil and ground water is constrained by the laws of thermodynamics. Bioremediation is being investigated in a rhizosphere environment in which higher plants provide carbon and energy to sustain the microbial population. Toluene, phenol, trichloroethylene and trichloroethane have been fed in separate experiments to a pilot scale system with alfalfa growing in sandy soil containing less than 10% of silt. It is well known that microbial populations are numerous in the root zone of healthy vegetation. Root exudates can stimulate aerobic microbial biodegradation of compounds which by themselves support growth poorly or not at all. Polynuclear aromatic compounds such as phenanthrene, anthracene, and pyrene, which are not very soluble in water, and chlorinated aliphatic hydrocarbons such as trichloroethylene are examples of compounds that can be biodegraded in the rhizosphere when root exudates are present to enhance and sustain microbial activity. Solar driven transport processes such as water and solute movements due to evapotranspiration increase the likelihood that the contaminants will come into contact with the microorganisms and be degraded. The thermodynamic and bioenergetic aspects of transport and biodegradation in the rhizosphere are examined through a review of the literature and the analysis of experimental data collected in the pilot scale system.     

Zn2+对土壤微生物碳、呼吸强度的影响

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New features of the steady-state rate related with the initial concentration of substrate in the diphenolase and monophenolase activities of tyrosinase

Tyrosinase has two types of enzymatic activities: the hydroxylation of monophenols to o-diphenols (monophenolase activity) and oxidation of o-diphenols to o-quinones (diphenolase activity). The action on o-diphenols involves two substrates: oxygen and o-diphenol, while the mechanism proposed is a Uni Uni Bi Bi ping-pong. In this contribution, we demonstrate experimentally that there is a kinetically preferred pathway, which translates into the appearance of curves of initial velocity vs. initial diphenol concentration shows inhibition by an excess of substrate, while sigmoid curves are obtained when the initial velocity vs. initial oxygen concentration are graphed. However, the action mechanism of the enzyme on monophenols, which is more complex because it involves three substrates (monophenol, oxygen and o-diphenol), does behave differently from the hyperbolic behaviour as regards the initial velocity vs. initial monophenol concentration, results that can be explained if the limiting step in the action of tyrosinase is the hydroxylation of monophenol to o-diphenol.