Spatio-temporal variability behavior of land surface soil water content in shrub- and grass-land

The knowledge of the relationship between spatial variability of the surface soil water content (theta) and its mean across a spatial domain (theta(m)) is crucial for hydrological modeling and understanding soil water dynamics at different scales. With the aim to compare the soil moisture dynamics and variability between the two land uses and to explore the relationship between the spatial variability of theta and theta(m), this study analyzed sets of surface theta measurements performed with an impedance soil moisture probe, collected 136 times during a period of one year in two transects covering different land uses, i.e., korshinsk peashrub transect (KPT) and bunge needlegrass transect (BNT), in a watershed of the Loess Plateau, China. Results showed that the temporal pattern of theta behaved similarly for the two land uses, with both relative wetter soils during wet period and relative drier soils during dry period recognized in BNT. Soil moisture tended to be temporally stable among different dates, and more stable patterns could be observed for dates with more similar soil water conditions. The magnitude of the spatial variation of theta in KPT was greater than that in ENT. For both land uses, the standard deviation (SD) of theta in general increased as theta(m) increased, a behavior that could be well described with a natural logarithmic function. Convex relationship of CV and theta(m) and the maximum CV for both land uses (43.5% in KPT and 41.0% in BNT) can, therefore, be ascertained. Geostatistical analysis showed that the range in KPT (9.1 m) was shorter than that in BNT (15.1 m). The nugget effects, the structured variability, hence the total variability increased as theta(m) increased. For both land uses, the spatial dependency in general increased with increasing theta(m). 2011 Elsevier B.V. All rights reserved.

Acidity and Aluminum Speciation as Affected by Surface Liming in Tropical No-Till Soils

Aluminum toxicity is one of the major soil factors limiting root growth in acidic soils. Because of the increase in organic matter content in the upper few centimeters of soils under no-till systems (NTS), most Al in soil solution may be complexed to dissolved organic C (DOC), thus decreasing its bioavailability. The aim of this study was to evaluate the effects of surface liming on Al speciation in soil solution in Brazilian sites under NTS. Field experiments were performed in two regions with contrasting climates and levels of soil acidity: Rondonopolis, Mato Grosso State, on a Rhodic Haplustox, and Ponta Grossa, Parana State, on a Typic Hapludox. The treatments consisted of a control and three lime rates, surface applied to raise the base saturation to 50, 70, and 90%. Soil solution was obtained at soil water equilibrium (1:1 w/w soil/water ratio). The effects of surface liming on soil chemical attributes and on the composition of the soil solution were dependent on weather conditions, time under NTS, and soil weathering. Most Al in soil solution was complexed to DOC, representing about 70 to 80% of the total Al at pH <5.0, and about 30 to 4096 at pH >5.0. Under pH 5.5, the results were closely correlated with the solubility line for amorphous Al. Organic complexes may control Al(3+) release into soil solution at pH <5.5. Results suggest that in areas under NTS for a long period of time, Al toxicity might decrease due to its complexation to high-molecular-weight organic compounds.

Endophytic Colonization of Potato (Solanum tuberosum L.) by a Novel Competent Bacterial Endophyte, Pseudomonas putida Strain P9, and Its Effect on Associated Bacterial Communities

Pseudomonas putida strain P9 is a novel competent endophyte from potato. P9 causes cultivar-dependent suppression of Phytophthora infestans. Colonization of the rhizoplane and endosphere of potato plants by P9 and its rifampin-resistant derivative P9R was studied. The purposes of this work were to follow the fate of P9 inside growing potato plants and to establish its effect on associated microbial communities. The effects of P9 and P9R inoculation were studied in two separate experiments. The roots of transplants of three different cultivars of potato were dipped in suspensions of P9 or P9R cells, and the plants were planted in soil. The fate of both strains was followed by examining colony growth and by performing PCR-denaturing gradient gel electrophoresis (PCR-DGGE). Colonies of both strains were recovered from rhizoplane and endosphere samples of all three cultivars at two growth stages. A conspicuous band, representing P9 and P9R, was found in all Pseudomonas PCR-DGGE fingerprints for treated plants. The numbers of P9R CFU and the P9R-specific band intensities for the different replicate samples were positively correlated, as determined by linear regression analysis. The effects of plant growth stage, genotype, and the presence of P9R on associated microbial communities were examined by multivariate and unweighted-pair group method with arithmetic mean cluster analyses of PCR-DGGE fingerprints. The presence of strain P9R had an effect on bacterial groups identified as Pseudomonas azotoformans, Pseudomonas veronii, and Pseudomonas syringae. In conclusion, strain P9 is an avid colonizer of potato plants, competing with microbial populations indigenous to the potato phytosphere. Bacterization with a biocontrol agent has an important and previously unexplored effect on plant-associated communities.

Surface Liming and Zinc Availability in a Long-Term Experiment under No-Till System

No-till (NT) system with crop rotation is one of the most effective strategies to improve agricultural sustainability in tropical and subtropical regions. To control soil acidity in NT, lime is broadcast on the surface without incorporation. The increase in soil pH due to surface liming may decrease zinc (Zn) availability and its uptake by crops. A field experiment was performed in Parana State, Brazil, on a loamy, kaolinitic, thermic Typic Hapludox to evaluate Zn bioavailability in a NT system after surface liming and re-liming. Dolomitic lime was surface applied on the main plots in July 1993 at the rates of 0, 2, 4, and 6 Mg ha-1. In June 2000, the main plots were divided in two subplots to study of the effect of surface re-liming at the rates of 0 and 3 Mg ha-1. The cropping sequence was soybean [Glycine max (L.) Merrill] (2001-2 and 2002-3), wheat (Triticum aestivum L.) (2003), soybean (2003-4), corn (Zea mays L.) (2004-5), and soybean (2005-6). Soil samples were collected at the following depths: 0-0.05, 0.05-0.10, and 0.10-0.20m, 10 years after surface liming and 3 years after surface re-liming. Soil Zn levels were extracted by four extractants: (i) 0.005molL-1 diethylenetriaminepentaacetic acid (DTPA) + 0.1molL-1 triethanolamine (TEA) + 0.01molL-1 calcium chloride (CaCl2) solution at pH7.3 (DTPA-TEA), (ii) 0.1molL-1 hydrochloric acid (HCl) solution, (iii) Mehlich 1 solution, and (iv) Mehlich 3 solution. Zinc concentrations in leaves and grains of soybean, wheat, and corn were also determined. Soil pH (0.01molL-1 CaCl2 suspension) varied from 4.4 to 6.1, at the 0- to 0.05-m depth, from 4.2 to 5.3 at the 0.05- to 0.10-m depth, and from 4.2 to 4.8 at the 0.10- to 0.20-m depth, after liming and re-liming. Zinc concentrations evaluated by DTPA-TEA, 0.1molL-1 HCl, Mehlich 1, and Mehlich 3 solutions were not changed as a result of lime rate application. Re-liming increased Zn concentrations extracted by 0.1molL-1 HCl at 0-0.05m deep and by DTPA-TEA at 0.05-0.10m deep. Surface-applied lime promoted a decrease in Zn concentrations of the crops, mainly in grains, because of increased soil pH at the surface layers. Regardless of the liming treatments, levels of Zn were sufficient to soybean, wheat, and corn nutrition under NT.

Podzolization as a deferralitization process: dynamics and chemistry of ground and surface waters in an Acrisol-Podzol sequence of the upper Amazon Basin

Hydrochemical processes involved in the development of hydromorphic Podzols are a major concern for the upper Amazon Basin because of the extent of the areas affected by such processes and the large amounts of organic carbon and associated metals exported to the rivers. The dynamics and chemical composition of ground and surface waters were studied along an Acrisol-Podzol sequence lying in an open depression of a plateau. Water levels were monitored along the sequence over a period of 2 years by means of piezometers. Water was sampled in zero-tension lysimeters for groundwater and for surface water in the drainage network of the depression. The pH and concentrations of organic carbon and major elements (Si, Fe and Al) were determined. The contrasted changes reported for concentrations of Si, organic carbon and metals (Fe, Al) mainly reflect the dynamics of the groundwater and the weathering conditions that prevail in the soils. Iron is released by the reductive dissolution of Fe oxides, mostly in the Bg horizons of the upslope Acrisols. It moves laterally under the control of hydraulic gradients and migrates through the iron-depleted Podzols where it is exported to the river network. Aluminium is released from the dissolution of Al-bearing minerals (gibbsite and kaolinite) at the margin of the podzolic area but is immobilized as organo-Al complexes in spodic horizons. In downslope positions, the quick recharge of the groundwater and large release of organic compounds lead to acidification and a loss of metals (mainly Al), previously stored in the Podzols.

Dosage-dependent shift in the spore community of arbuscular mycorrhizal fungi following application of tannery sludge

The controlled disposal of tannery sludge in agricultural soils is a viable alternative for recycling such waste; however, the impact of this practice on the arbuscular mycorrhizal fungi (AMF) communities is not well understood. We studied the effects of low-chromium tannery sludge amendment in soils on AMF spore density, species richness and diversity, and root colonization levels. Sludge was applied at four doses to an agricultural field in Rolandia, Parana state, Brazil. The sludge was left undisturbed on the soil surface and then the area was harrowed and planted with corn. The soil was sampled at four intervals and corn roots once within a year (2007/2008). AMF spore density was low (1 to 49 spores per 50 cm(3) of soil) and decreased as doses of tannery sludge increased. AMF root colonization was high (64%) and unaffected by tannery sludge. Eighteen AMF species belonging to six genera (Acaulospora, Glomus, Gigaspora, Scutellospora, Paraglomus, and Ambispora) were recorded. At the sludge doses of 9.0 and 22.6 Mg ha(-1), we observed a decrease in AMF species richness and diversity, and changes in their relative frequencies. Hierarchical grouping analysis showed that adding tannery waste to the soil altered AMF spore community in relation to the control, modifying the mycorrhizal status of soil and selectively favoring the sporulation of certain species.

Components of Surface Charge in Tropical Soils With Contrasting Mineralogies

Study of surface electric charges of soil colloids helps in understanding the physicochemical phenomena that influence the capacity of retaining nutrients and their availability to plants. The structural charge (sigma(0), (min)), the variable charge (sigma(q, min)), and the organic matter (OM) charge (sigma(total) (OM)) of 12 tropical soils with contrasting mineralogies were evaluated based on the difference of selectivity for Cs(+) and Li(+) between the functional ionizable surfaces groups and the mineral 2:1 siloxane surface. Soils were divided into three groups: G1, soils with a predominance of kaolinite and gibbsite in the clay fraction; G2, soils with hydroxy-interlayered 2:1 minerals; and G3, soils with smectite but without hydroxy-interlayered 2:1 minerals. The Cs absorption method was efficient for detecting the charge components in tropical soils. The mineral structural charge contributed 11% and 16%, 28% and 31%, and 52% and 59% of total soil charge of A and B horizons of soils from groups G 1, G2, and G3, respectively. On the other hand, OM contributed 53% and 37%, 48% and 41%, and 21% and 20% of total charge for the same samples, respectively, In highly weathered soils of group G I and, to a lesser extent, in soils in group G2, surface charges depended mainly on their variable components, resulting from the OM (sigma(toal) (OM)), as well as from imperfections found in 1:1 minerals (sigma(q, min)). The importance of OM in determining the magnitude of electric charges in humid tropical soils is highlighted.

Fate of Surface-Inoculated Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on Kippered Beef during Extended Storage at Refrigeration and Abusive Temperatures

The behavior of Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium on kippered beef was evaluated. Individual pieces of the product were separately inoculated on the top and bottom surfaces with each three- to six-strain pathogen cocktail at ca. 6.0 log CFU per piece and stored at 4, 10, 21, or 30 degrees C for up to 28 days in each of two trials. When kippered beef was inoculated with E coli O157:H7, Salmonella Typhimurium, or L. monocytogenes and stored at 4, 10, 2 1, or 30 degrees C for up to 28 days, pathogen numbers decreased ca. 0.4 to 0.9, 1.0 to 1.8, 3.0 to >= 5.25, and >= 5.0 to 5.25 log CFU per piece, respectively. Average D-values for E. coli O157:H7, Salmonella Typhimurium, and L. monocytogenes stored at 4 to 30 degrees C for 28 days were ca. 41 to 4.6, 40.8 to 5.3, and 29.5 to 4.3 days, respectively. As expected, the higher the storage temperature, the greater the level and rate of inactivation for all three pathogens. These data establish that kippered beef does not provide an environment conducive to proliferation of these pathogens.

Diversity of endophytic bacteria from Eucalyptus species seeds and colonization of seedlings by Pantoea agglomerans

The diversity and beneficial characteristics of endophytic microorganisms have been studied in several host plants. However, information regal-ding naturally, occurring seed-associated endophytes and vertical transmission among different life-history stages of hosts is limited. Endophytic bacteria were isolated from seeds and seedlings of 10 Eucalyptus species and two hybrids. The results showed that endophytic bacteria, Such as Bacillus, Enterococcus, Paenibacillus and Methylobacterium, are vertically transferred from seeds to seedlings. In addition, the endophytic bacterium Pantoea agglomerans was tagged with the gfp gene, inoculated into seeds and further reisolated from seedlings. These results suggested it novel approach to change the profile of the plants, where the bacterium is a delivery vehicle for desired traits. This is the first report of an endophytic bacterial community residing in Eucalyptus seeds and the transmission of these bacteria from seeds to seedlings. The bacterial species reported ill this work have been described as providing benefits to host plants. Therefore, we Suggest that endophytic bacteria can be transmitted vertically from seeds to seedlings, assuring the support of the bacterial community in the host plant.

Sensory evaluation and physicochemical optimisation of soy-based desserts using response surface methodology

The objective of this study was to develop a dessert that contains soy protein (SP) (1%, 2%, 3%) and guava juice (GJ) (22%, 27%, 32%) using Response Surface Methodology (RSM) as the optimisation technique. Water activity, physical stability, colour, acidity, pH, iron, and carotenoid contents were analysed. Affective tests were performed to determine the degree of liking of colour, creaminess, and acceptability. The results showed that GJ increased the values of redness, hue angle, chromaticity, acidity, and carotenoid content, while SP reduced water activity. Optimisation suggested a dessert containing 32% GJ and 1.17% SP as the best proportion of these components. This sample was considered a source of fibres, ascorbic acid, copper, and iron and garnered scores above the level of `slightly liked` for sensory attributes. Moreover, RSM was shown to be an adequate approach for modelling the physicochemical parameters and the degree of liking of creaminess of desserts. (C) 2010 Elsevier Ltd. All rights reserved.

Physical Stability Assessment and Sensory Optimization of a Dairy-Free Emulsion Using Response Surface Methodology

Desserts made with soy cream, which are oil-in-water emulsions, are widely consumed by lactose-intolerant individuals in Brazil. In this regard, this study aimed at using response surface methodology (RSM) to optimize the sensory attributes of a soy-based emulsion over a range of pink guava juice (GJ: 22% to 32%) and soy protein (SP: 1% to 3%). WHC and backscattering were analyzed after 72 h of storage at 7 degrees C. Furthermore, a rating test was performed to determine the degree of liking of color, taste, creaminess, appearance, and overall acceptability. The data showed that the samples were stable against gravity and storage. The models developed by RSM adequately described the creaminess, taste, and appearance of the emulsions. The response surface of the desirability function was used successfully in the optimization of the sensory properties of dairy-free emulsions, suggesting that a product with 30.35% GJ and 3% SP was the best combination of these components. The optimized sample presented suitable sensory properties, in addition to being a source of dietary fiber, iron, copper, and ascorbic acid.

Cell surface expression of adhesins for fibronectin correlates with virulence in Sporothrix schenckii

The virulence of four Sporothrix schenckii isolates was compared in a murine model of sporotrichosis, together with the protein pattern of the yeast cell surface and the capacity to bind the extracellular matrix protein fibronectin. Virulence was determined by the mortality rate, fungal burden and histopathology. Two clinical isolates were more virulent for C57BL/6 mice, but no direct correlation was seen between virulence and the clinical or environmental origin of the isolates. The lowest virulence was observed for an isolate recovered from a patient with meningeal sporotrichosis. Although all isolates could effectively disseminate, the dissemination patterns were not similar. Using flow cytometry analysis, we investigated the interaction of all the strains with fibronectin, and showed that the binding capacity correlated with virulence. Western blot analysis of S. schenckii cell wall extracts revealed positive bands for fibronectin in the range of 3792 kDa. The 70 kDa adhesin was also recognized by a protective monoclonal antibody raised against a gp70 antigen of S. schenckii (mAb P6E7). Confocal microscopy confirmed the co-localization of fibronectin and mAb P6E7 on the yeast cell surface. To our knowledge, this is the first report identifying adhesins for fibronectin on the surface of this human pathogen.

Biophysical characterization of the recombinant merozoite surface protein-3 of Plasmodium vivax

Plasmodium vivax Merozoite Surface Protein-3 alpha and 3 beta are members of a family of related merozoite surface proteins that contain a central alanine-rich domain with heptad repeats that is predicted to form alpha-helical secondary and coiled-coil tertiary structures. Seven recombinant proteins representing different regions of MSP-3 alpha and MSP-3 beta of P. vivax were generated to investigate their structure. Circular dichroism spectra analysis revealed that some proteins are folded with a high degree of alpha-helices as secondary structure, whereas other products contain a high content of random coil. Using size exclusion chromatography, we found that the two smaller fragments of the MSP-3 alpha, named CC4 and CC5, predicted to form coiled-coil (CC) structures, eluted at volumes corresponding to molecular weights larger than their monomeric masses. This result suggests that both proteins are oligomeric molecules. Analytical ultracentrifugation experiments showed that the CC5 oligomers are elongated molecules. Together, these data may help to understand important aspects of P. vivax biology. (C) 2008 Elsevier B.V. All rights reserved.

Human Airway Epithelial Cell Responses to Neisseria lactamica and Purified Porin via Toll-Like Receptor 2-Dependent Signaling

The human airway epithelium is constantly exposed to microbial products from colonizing organisms. Regulation of Toll-like receptor (TLR) expression and specific interactions with bacterial ligands is thought to mitigate exacerbation of inflammatory processes induced by the commensal flora in these cells. The genus Neisseria comprises pathogenic and commensal organisms that colonize the human nasopharynx. Neisseria lactamica is not associated with disease, but N. meningitidis occasionally invades the host, causing meningococcal disease and septicemia. Upon colonization of the airway epithelium, specific host cell receptors interact with numerous Neisseria components, including the PorB porin, at the immediate bacterial-host cell interface. This major outer membrane protein is expressed by all Neisseria strains, regardless of pathogenicity, but its amino acid sequence varies among strains, particularly in the surface-exposed regions. The interaction of Neisseria PorB with TLR2 is essential for driving TLR2/TLR1-dependent cellular responses and is thought to occur via the porin`s surface-exposed loop regions. Our studies show that N. lactamica PorB is a TLR2 ligand but its binding specificity for TLR2 is different from that of meningococcal PorB. Furthermore, N. lactamica PorB is a poor inducer of proinflammatory mediators and of TLR2 expression in human airway epithelial cells. These effects are reproduced by whole N. lactamica organisms. Since the responsiveness of human airway epithelial cells to colonizing bacteria is in part regulated via TLR2 expression and signaling, commensal organisms such as N. lactamica would benefit from expressing a product that induces low TLR2-dependent local inflammation, likely delaying or avoiding clearance by the host.

Processing optimization of probiotic yogurt containing glucose oxidase using response surface methodology

Exposure to oxygen may induce a lack of functionality of probiotic dairy foods because the anaerobic metabolism of probiotic bacteria compromises during storage the maintenance of their viability to provide benefits to consumer health. Glucose oxidase can constitute a potential alternative to increase the survival of probiotic bacteria in yogurt because it consumes the oxygen permeating to the inside of the pot during storage, thus making it possible to avoid the use of chemical additives. This research aimed to optimize the processing of probiotic yogurt supplemented with glucose oxidase using response surface methodology and to determine the levels of glucose and glucose oxidase that minimize the concentration of dissolved oxygen and maximize the Bifidobacterium longum count by the desirability function. Response surface methodology mathematical models adequately described the process, with adjusted determination coefficients of 83% for the oxygen and 94% for the B. longum. Linear and quadratic effects of the glucose oxidase were reported for the oxygen model, whereas for the B. longum count model an influence of the glucose oxidase at the linear level was observed followed by the quadratic influence of glucose and quadratic effect of glucose oxidase. The desirability function indicated that 62.32 ppm of glucose oxidase and 4.35 ppm of glucose was the best combination of these components for optimization of probiotic yogurt processing. An additional validation experiment was performed and results showed acceptable error between the predicted and experimental results.