[show abstract][hide abstract] ABSTRACT: The genus Geolegnia represents a poorly documented group of saprolegnialean oomycetes isolated from soils as free-living organisms. Although it is morphologically similar to the facultative parasitic genus Leptolegnia, Geolegnia presents the uncommon property of having lost a flagellate stage in its lifecycle. Based on ITS and large subunit (LSU) rRNA sequence data, we show Geolegnia to be basal to Leptolegnia, and also introduce Geolegnia helicoides sp. nov. Using sequence data of Leptolegnia available in GenBank, supplemented by data derived from culture collections, we show that Geolegnia is nested within Leptolegnia, a genus characterised by its "conventional" biflagellate life cycle. The emergence of Geolegnia is therefore seen as a recent event, and we suggest here an evolutionary context where this loss might have been advantageous. Based on this study, Leptolegnia remains paraphyletic, awaiting the redefinition of genera in this complex.
[show abstract][hide abstract] ABSTRACT: The search for novel microorganisms able to degrade olive mill wastewaters (OMW) and withstand the toxic effects of the initially high phenolic concentrations is of great scientific and industrial interest. In this work, the possibility of reducing the phenolic content of OMW using new isolates of fungal strains (Coriolopsis gallica, Bjerkandera adusta, Trametes versicolor, Trichoderma citrinoviride, Phanerochaete chrysosporium, Gloeophyllum trabeum, Trametes trogii, and Fusarium solani) was investigated. In vitro, all fungal isolates tested caused an outstanding decolorization of OMW. However, C. gallica gave the highest decolorization and dephenolization rates at 30 % v/v OMW dilution in water. Fungal growth in OMW medium was affected by several parameters including phenolic compound concentration, nitrogen source, and inoculum size. The optimal OMW medium for the removal of phenolics and color was with the OMW concentration (in percent)/[(NH4)2SO4]/inoculum ratio of 30:6:3. Under these conditions, 90 and 85 % of the initial phenolic compounds and color were removed, respectively. High-pressure liquid chromatography analysis of extracts from treated and untreated OMW showed a clear and substantial reduction in phenolic compound concentrations. Phytotoxicity, assessed using radish (Raphanus sativus) seeds, indicated an increase in germination index of 23-92 % when a 30 % OMW concentration was treated with C. gallica in different dilutions (1/2, 1/4, and 1/8).
Environmental Science and Pollution Research 08/2013; · 2.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: Ceratocystis platani is the causal agent of canker stain of plane trees, a lethal disease, able to kill mature trees in one or two successive growing seasons. The pathogen is a quarantine organism and has a negative impact on anthropogenic and natural populations of plane trees. Contaminated sawdust produced during pruning and sanitation fellings can contribute to disease spread. The goal of this study was to design a rapid, real-time quantitative PCR assay to detect C. platani airborne inoculum. Airborne inoculum traps (AITs), were placed in an urban in the city of Florence (Italy), where the disease was present. Primers and TaqMan® MGB probes were designed to target cerato-platanin (CP) and internal transcribed spacer (ITS2) genes. The detection limit of the assay was 0.05 pg/μl and 2 fg/μl of fungal DNA for CP and ITS, respectively. Pathogen detection directly from AITs demonstrated specificity and high sensitivity for C. platani detecting DNA concentrations as low as 1.2-1.4 x10(-2) pg/μl, corresponding to approximately 10 conidia per ml. Airborne inoculum traps were able to detect C. platani inoculum within 200 meters of the closest symptomatic infected plane tree. The combination of airborne trapping and real-time quantitative PCR assay provides a rapid and sensitive method for the specific detection of C. platani inoculum. This technique may be used to identify the period of highest risk of pathogen spread in a site, thus helping the disease management.
Applied and environmental microbiology 06/2013; · 3.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this work was to determine the optimal conditions for the decolorization and the detoxification of two effluents from a textile industry-effluent A (the reactive dye bath Bezactive) and effluent B (the direct dye bath Tubantin)-using a laccase mediator system. Response surface methodology (RSM) was applied to optimize textile effluents decolorization. A Box-Behnken design using RSM with the four variables pH, effluent concentration, 1-hydroxybenzotriazole (HBT) concentration, and enzyme (laccase) concentration was used to determine correlations between the effects of these variables on the decolorization of the two effluents. The optimum conditions for pH and concentrations of HBT, effluent and laccase were 5, 1 mM, 50 % and 0.6 U/ml, respectively, for maximum decolorization of effluent A (68 %). For effluent B, optima were 4, 1 mM, 75 %, and 0.6 U/ml, respectively, for maximum decolorization of approximately 88 %. Both effluents were treated at 30 °C for 20 h. A quadratic model was obtained for each decolorization through this design. The experimental and predicted values were in good agreement and both models were highly significant. In addition, the toxicity of the two effluents was determined before and after laccase treatment using Saccharomyces cerevisiae, Bacillus cereus, and germination of tomato seeds.
Environmental Science and Pollution Research 01/2013; · 2.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: A group of protist experts proposes a two-step DNA barcoding approach, comprising a universal eukaryotic pre-barcode followed by group-specific barcodes, to unveil the hidden biodiversity of microbial eukaryotes.
[show abstract][hide abstract] ABSTRACT: Response surface methodology (RSM) was applied to optimize the decolourization of 3 dyes belonging to 3 dye families such as reactive black 5 (diazoic), indigo carmine (indigoid) and aniline blue (anthraquinonic). Crude laccase from Trametes trogii and the laccase-mediator 1-hydroxybenzotriazole (HBT) were used in this study. Box-Behnken design using RSM with six variables namely pH, temperature, enzyme concentration, HBT concentration, dye concentration and incubation time was used in this study to optimize significant correlation between the effects of these variables on the decolourization of reactive black 5 (RB5), indigo carmine (IC) and aniline blue (AB). The optimum of pH, temperature, laccase, HBT, RB5 and reaction time were 4.5, 0.5 U ml(-1), 0.5 mM, 100 mg ml(-1) and 150 min respectively, for a maximum decolourization of RB5 (about 92.92% ± 7.21). Whereas, the optimum decolourization conditions of both IC (99.76% ± 7.75) and AB (98.44% ± 10) were: pH 4.5, temperature of 45 °C, enzyme concentration of 0.1 U ml(-1) and 0.5 U ml(-1), HBT concentration of 0.9 mM and 0.5 mM, dye concentration of 60 mg l(-1) and reaction time of 150 and 90 min, respectively. The experimental values were in good agreement with the predicted ones and the models were highly significant, the correlation coefficient (R(2)) being 0.864, 0.663 and 0.776 for RB5, IC and AB, respectively. In addition, when the kinetic parameters for the three dyes decolourization were calculated according to Hannes-Wolf plot, the following values were obtained: Km of 268.4, 47.94 and 44.64 mg l(-1) then V(max) of 35.58, 10.43 and 9.23 mg l(-1) min for the RB5, IC and AB decolourizations by laccase, respectively.
Journal of Environmental Management 05/2012; 108:84-91. · 3.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: Parasitism and saprotrophic wood decay are two fungal strategies fundamental for succession and nutrient cycling in forest ecosystems. An opportunity to assess the trade-off between these strategies is provided by the forest pathogen and wood decayer Heterobasidion annosum sensu lato. We report the annotated genome sequence and transcript profiling, as well as the quantitative trait loci mapping, of one member of the species complex: H. irregulare. Quantitative trait loci critical for pathogenicity, and rich in transposable elements, orphan and secreted genes, were identified. A wide range of cellulose-degrading enzymes are expressed during wood decay. By contrast, pathogenic interaction between H. irregulare and pine engages fewer carbohydrate-active enzymes, but involves an increase in pectinolytic enzymes, transcription modules for oxidative stress and secondary metabolite production. Our results show a trade-off in terms of constrained carbohydrate decomposition and membrane transport capacity during interaction with living hosts. Our findings establish that saprotrophic wood decay and necrotrophic parasitism involve two distinct, yet overlapping, processes.
New Phytologist 03/2012; 194(4):1001-13. · 6.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: The chemical composition and some biological properties of four algae (Ulva rigida, Codium bursa, Cystoseira barbata, and
Ceramium diaphanum) collected from the Gabes Gulf area (Tunisia) were examined. Ash (11.35–29.08% weight/dry weight [w/dw]) and
total sugar (13.20–18.70% w/dw) were the most abundant contents in these algae. Protein contents were moderate (5.03–14.00% w/dw), with
the red alga (C. diaphanum) having the highest value. Lipid contents were within the range mentioned for seaweeds (<3% w/dw). Saturated
fatty acids occurring at the highest proportions were C16:0 (24.53–41.37%) and C12:0 (10.37–24.44%). The most abundant monounsaturated
fatty acid was C18:1n-9 (21.74–54.22%), whereas the most abundant polyunsaturated fatty acid was C18:2n-6 (9.57–11.71%). Variations in
chemical composition can be attributed to both environmental and genetic differences among species. All algal extracts displayed antibacterial
activity against Escherichia coli and Staphylococcus simulans (inhibition diameter: 10–25 mm), antioxidant activity (radical scavenging
activity: 0.8–23%), and anti-inflammatory activity (48–61% inhibition of the phospholipase A2 activity); therefore, the marine algae examined
can be considered abundant resources of bioactive molecules.
[show abstract][hide abstract] ABSTRACT: This paper is an extension of our previous experimental results to the numerical prediction of the dissociation process relative to cellulase enzymes with increasing temperatures. We have computed the quantities of interest, that is, the pair correlation and bridge functions, using integral equation theory with an appropriate closure relation. The central result of our work is the existence of the cut-off distance; above it the attractive tail of the Lennard–Jones potential becomes negligible and the enzymes reach their globular conformation. The effects of temperature, number density, and potential parameters on the pair correlation and bridge functions are also discussed.
Journal of Macromolecular Science. 01/2011; Part B(Vol. 50):33-40.
[show abstract][hide abstract] ABSTRACT: Traditional farming system is an ecologically based age-old farming system developed by ancient farmers through generations of their interaction with nature and natural resources for food, fodder and fiber. Indigenous knowledge is the knowledge of the indigenous people inhabiting different geographical regions of the world with their own language, culture, tradition, belief, folklore, rites and rituals. This report is an attempt to document some of the indigenous practices followed by traditional farmers for the management of pests of certain common crops grown in traditional farms in general and north east India in particular.
Journal of Plant Breeding and Crop Science. 04/2009; 1:28-38.
[show abstract][hide abstract] ABSTRACT: Transgenic Phytophthora ramorum strains that produce green fluorescent protein (GFP) constitutively were obtained after stable DNA integration using a polyethylene glycol and CaCl₂-based transformation protocol. Green fluorescent protein production was studied in developing colonies and in different propagules of the pathogen to evaluate its use in molecular and physiological studies. About 12% of the GFP transformants produced GFP to a level detectable by a confocal laser scanning microscope. Green fluorescent protein could be visualized in structures with vital protoplasm, such as hyphal tips and germinating cysts. In infection studies with Rhododendron, one of the GFP expressing strains showed aggressiveness equal to that of the corresponding non-labelled isolate. Thus, GFP could be used as a reporter gene in P. ramorum. Limitations of the technology are discussed.
Journal of Eukaryotic Microbiology 01/2009; 56(2):130-5. · 2.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: The objective of this study was to demonstrate that fish-processing by-products could be used as sole raw material to sustain the growth of Staphylococcus xylosus for lipase production.
Bacterial growth was tested on supernatants generated by boiling (100 degrees C for 20 min) of tuna, sardine, cuttlefish and shrimp by-products from fish processing industries. Among all samples tested, only supernatants generated from shrimp and cuttlefish by-products sustained the growth of S. xylosus. Shrimp-based medium gave the highest growth (A(600) = 22) after 22 h of culture and exhibited the maximum lipase activity (28 U ml(-1)). This effect may be explained by better availability of nutrients, especially, in shrimp by-products. Standard medium (SM) amendments to sardine and tuna by-product-based media stimulated the growth of S. xylosus and the highest A(600) values were obtained with 75% SM. Lipase activity, however, remained below 4 U ml(-1) for both sardine and tuna by-product-based media.
Fish by-products could be used for the production of highly valuable enzymes.
The use of fish by-products in producing S. xylosus-growth media can reduce environmental problems associated with waste disposal and, simultaneously, lower the cost of biomass and enzyme production.
Letters in Applied Microbiology 01/2009; 47(6):549-54. · 1.63 Impact Factor
[show abstract][hide abstract] ABSTRACT: The present study extends the viscosity measurements performed by Ghaouar et al. [Physica B, submitted for publication.] to study the conformational change of the cellulase enzymes in aqueous-acetonitrile mixture. We aim to investigate: (i) the denaturation process by measuring the specific viscosity for temperatures varying between 25 and 65°C and acetonitrile concentrations between 0% and 50%, (ii) the enzyme–enzyme interaction by calculating the Huggins coefficient and (iii) the enzyme sizes by following the hydrodynamic radius for various temperatures. The precipitation of cellulases versus acetonitrile concentration is also considered. We show from all physical quantities measured in this work that the precipitation and the denaturation processes of cellulase enzymes exist together.
Physica B Condensed Matter 01/2009; 404(21):4257-4261. · 1.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: The behaviour of cellulase enzymes in phosphate saline buffer has been studied over a wide range of temperatures and enzyme concentrations by using viscosity measurements. To characterize the conformation change of cellulase versus temperature and chemical denaturants, such as guanidinium chloride (GdmCl) and urea, the information about the intrinsic viscosity and the hydrodynamic radius are necessary. The dependence of the intrinsic viscosity and the hydrodynamic radius in its random coil conformation on temperature and denaturant concentration were studied. Our results and discussions are limited to the dilute regime of concentration because of abnormalities in conformation observed in the very dilute regime due to the presence of capillary absorption effects.
Physica B Condensed Matter 01/2009; 404(21):4246-4252. · 1.33 Impact Factor
[show abstract][hide abstract] ABSTRACT: The decolourization and detoxification of the triarylmethane dye Malachite green (MG) by laccase from Trametes sp. were investigated. The laccase decolorized efficiently the dye down to 97% of 50 mg L−1 initial concentration of MG when only 0.1 U mL−1 of laccase was used in the reaction mixture. The effects of different physicochemical parameters were tested and optimal decolourization rates occurred at pH 6 and at temperatures between 50 and 60 °C. Decolourization of MG occurred in the presence of metal ions which could be found in textile industry effluent. 1-hydroxybenzotriazole (HBT) affected positively the decolourization of MG. The presence of some phenolic compounds namely ferulic, coumaric, gallic, and tannic acids was found to be inhibiting for the decolourization at a concentration of 10 mM.The effect of laccase inhibitors in the decolourization of MG was tested with l-cysteine, and ethylene diamine tetra-acetic acid (EDTA) at concentrations of 0.1, 1 and 10 mM. It was demonstrated that l-cysteine and EDTA inhibited the decolourization starting from 1 mM concentration. However, for NaCl a concentration of 100 mM was needed for the inhibition of laccase. The decolourization of MG resulted in the removal of its toxicity against Phanerochaete chrysosporium.The stability of the laccase toward temperature and HBT free radicals was also assessed during MG decolourization. It was shown that laccase was stable at 50 °C but in the presence of the laccase mediator HBT, the stability of the enzyme was severely affected resulting in a loss of 50% of the activity after 3 h incubation.
International Biodeterioration & Biodegradation - INT BIODETERIOR BIODEGRAD. 01/2009; 63(5):600-606.
[show abstract][hide abstract] ABSTRACT: In our study, the potential of producing polyhydroxybutyrate (PHB) by cultivating fast-growing rhizobia (Sinorhizobium meliloti, Rhizobium leguminosarum bv. viciae, R. leguminosarum bv. phaseoli and R. leguminosarum bv. trifolii) in sludge and in industrial wastewater was evaluated. Results confirmed the possibility of using sludge as media for rhizobial growth. During growth, substantial quantity of PHB was accumulated and yields varied depending on the media and rhizobial species. Growing in sludge, PHB production did not exceed 3.7% w/w for all strains at the end of experiment (after 72 h). During the growth of S. meliloti, PHB yield varied and the maximum value reached 7.27% w/w after 60 h, with 1% Total Suspend Solid (TSS) sludge. Alkaline sludge pre-treatment affects rhizobial growth but did not improve the PHB accumulation. While growing S. meliloti in industrial wastewater, the PHB yields varied and the highest value was obtained with slaughterhouse wastewater (10.7% w/w) after 35 h of growth. Therefore, this work shows the potential of exploiting PHB production by rhizobia growing in wastewater or sludge which could be applied to bioplastic industry, and confirms the potential of these recyclable wastes for high production of rhizobial cells useable for legumes inoculants production. This study provides an environmentally sound way of sludge and wastewater management and use in diverse biotechnological applications.
Applied biochemistry and biotechnology 10/2008; 158(1):155-63. · 1.94 Impact Factor
[show abstract][hide abstract] ABSTRACT: During surveys for Phytophthora ramorum in garden centres in Majorca, Spain, 31 isolates of Phytophthora were recovered from potted strawberry trees (Arbutus unedo) showing leaf and twig blights. Many isolates of Phytophthora syringae and Phytophthora citrophthora as well as single isolates of P. ramorum, Phytophthora tropicalis and Phytophthora nicotianae were identified on morphological features and on the sequences of the internal transcribed spacer regions from ribosomal DNA genes. Phytophthora syringae was collected most frequently in late autumn and winter, whereas P. citrophthora was dominant during late summer and autumn. In vitro pathogenicity of P. syringae and P. citrophthora was compared with that of P. ramorum by inoculating intact detached leaves of A. unedo with zoospores and twigs with mycelial plugs. In addition, in vitro sporangial production was examined on inoculated excised leaves and on agar plugs at 12, 15 and 20°C. Phytophthora citrophthora produced the largest lesions both on leaves and on twigs at all temperatures. Phytophthora ramorum formed lesions comparable in size to those of P. syringae, but it significantly produced more sporangia on excised leaves and agar plugs. In a log inoculation assay, P. syringae caused large lesions in the inner bark, whereas those of P. ramorum were moderate. Strawberry tree blight has not yet been observed in natural ecosystems in the western Mediterranean areas. Possible biological and environmental limitations hindering disease spread in the wild are discussed.