Lassaad Belbahri

Université de Neuchâtel, Neuenburg, Neuchâtel, Switzerland

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Publications (57)132.47 Total impact

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    ABSTRACT: A non-papillate, heterothallic Phytophthora species first isolated in 2001 and subsequently from symptomatic roots, crowns and stems of 33 plant species in 25 unrelated botanical families from 13 countries is formally described here as a new species. Symptoms on various hosts included crown and stem rot, chlorosis, wilting, leaf blight, cankers and gumming. This species was isolated from Australia, Hungary, Israel, Italy, Japan, the Netherlands, Norway, South Africa, Spain, Taiwan, Turkey, the United Kingdom and United States in association with shrubs and herbaceous ornamentals grown mainly in greenhouses. The most prevalent hosts are English ivy (Hedera helix) and Cistus (Cistus salvifolius). The association of the species with acorn banksia (Banksia priorates) plants in natural ecosystems in Australia, in affected vineyards (Vitis vinifera) in South Africa and almond (Prunus dulcis) trees in Spain and Turkey in addition to infection of shrubs and herbaceous ornamentals in a broad range of unrelated families are a sign of a wide ecological adaptation of the species and its potential threat to agricultural and natural ecosystems. The morphology of the persistent non-papillate ellipsoid sporangia, unique toruloid lobate hyphal swellings and amphigynous antheridia does not match any of the described species. Phylogenetic analysis based on sequences of the ITS rDNA, EF- 1α and β-tub supported that this organism is a hitherto unknown species. It is closely related to species in ITS clade 7b with the most closely related species being P. sojae. The name Phytophthora niederhauserii has been used in previous studies without the formal description of the holotype. This name is validated in this manuscript with the formal description of Phytophthora niederhauserii Z.G. Abad et J.A. Abad, sp. nov. The name is coined to honor Dr John S. Niederhauser, a notable plant pathologist and the 1990 World Food Prize laureate.
    Mycologia 05/2014; · 2.11 Impact Factor
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    ABSTRACT: Diversity of the microbial consortia involved in biodegradation of unhairing wastewater from tanneries was assessed. Both culture-dependent and culture-independent approaches were applied to identify bacteria in the activated sludge and endogenous biomass systems. Conventional culturing using dilution and planting techniques yielded eighteen pure bacterial isolates from endogenous biomass and activated sludge reactors. Isolates were identified using sequence analysis of PCR-amplified 16S rRNA sequences. Most of these bacteria belonged to the genus Bacillus. Culture-independent molecular studies of bacterial diversity in both reactors, however, revealed a wide diversity of microorganisms, including members of the Proteobacteria group. Therefore, the alpha Proteobacteria group in the endogenous biomass was characterized by the genus Pseudochrobactrum, which was absent from the activated sludge biomass. The 77 and 88 bacterial clone sequences recovered from the activated sludge reactor and the endogenous biomass reactor, respectively, were grouped into 23 Operational Taxonomic Units (OTUs). The Proteobacteria division represented the predominant phylogenetic group within the clone library, encompassing 52.17% and 60.75% of the total OTUs obtained from the activated sludge and endogenous biomass tanks, respectively. The diversity in both tanks was also determined. The rarefaction curves and Shannon index indicated that bacterial populations were equally diverse in both reactors. © 2014 American Institute of Chemical Engineers Environ Prog, 2014
    Environmental Progress & Sustainable Energy 05/2014; · 0.87 Impact Factor
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    ABSTRACT: Olive mill wastewaters (OMW) pose a serious environmental concern owing to high polyphenol content. Decolorization and degradation of phenolic compounds (PC) by Coriolopsis gallica was demonstrated in our laboratory as a potential biotreatment of OMW in solid and liquid media. High performance liquid chromatography coupled to electrospray time-of-flight mass spectrometry was used to analyze the evolution of the main phenolic compounds during the C. gallica biodegradation process. Amongst total the compounds characterized in methanolic extracts of OMW, 12 were unknown, 15 were from different polyphenolic families, and 27 were other non-phenolic compounds. The evolution of PC content during the degradation process indicated that, despite the complexity of the OMW phenolic fraction, C. gallica was able to grow on OMW-based media using PC as sources of carbon and energy, particularly acids, alcohols, lignans and flavones. Complete dephenolization of OMW was obtained.
    Chemosphere 01/2014; · 3.14 Impact Factor
  • Chemosphere 01/2014; 113:62–70. · 3.14 Impact Factor
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    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.
    IMA fungus. 12/2013; 4(2):169-75.
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    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; · 2.76 Impact Factor
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    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; · 3.95 Impact Factor
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    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; · 2.76 Impact Factor
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    ABSTRACT: Invasive oomycete pathogens have been causing significant damage to native ecosystems worldwide for over a century. A recent well‐known example is Phytophthora ramorum, the causal agent of sudden oak death, which emerged in the 1990s in Europe and North America. In Europe, this pathogen is mainly restricted to woody ornamentals in nurseries and public greens, while severe outbreaks in the wild have only been reported in the UK. This study presents the results of the P. ramorum survey conducted in Swiss nurseries between 2003 and 2011. In all 120 nurseries subjected to the plant passport system, the main P. ramorum hosts were visually checked for above ground infections. Phytophthora species were isolated from tissue showing symptoms and identified on the basis of the morphological features of the cultures and sequencing of the ribosomal ITS region. Phytophthora was detected on 125 plants (66 Viburnum, 58 Rhododendron and one Pieris). Phytophthora ramorum was the most frequent species (59·2% of the plants), followed by P. plurivora, P. cactorum, P. citrophthora, P. cinnamomi, P. cactorum/P. hedraiandra, P. multivora and P. taxon PgChlamydo. The highest incidence of P. ramorum was observed on Viburnum × bodnantense. Microsatellite genotyping showed that the Swiss P. ramorum population is highly clonal and consists of seven genotypes (five previously reported in Europe, two new), all belonging to the European EU1 clonal lineage. It can therefore be assumed that P. ramorum entered Switzerland through nursery trade. Despite sanitation measures, repeated P. ramorum infections have been recorded in seven nurseries, suggesting either reintroduction or unsuccessful eradication efforts.
    Plant Pathology 01/2013; · 2.73 Impact Factor
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    ABSTRACT: Cork oaks (Quercus suber L.) are key tree species at Doñana Biological Reserve (DBR), Huelva, Spain. Sampling was conducted on a total of 13 trees exhibiting symptoms of decline (foliar wilting and defoliation, branch dieback and root necrosis). In 2008 Phytophthora cinnamomi was isolated from feeder roots of one tree and Pythium spiculum from two additional oaks. In 2011, both pathogens were isolated from 6 oaks, only P. cinnamomi from 3 oaks and only Py. spiculum from 1 oak. This expansion was associated with high winter rainfall levels since 2009 that led to long periods of soil flooding. While P. cinnamomi is well known to cause a root disease on Q. suber (1), P. spiculum is a newly described species isolated from Quercus, Vitis, Prunus, Castanea and Celtis species, but its pathogenicity was demonstrated only on Q. ilex (syn. Q. rotundifolia) (2). Pathogenicity tests were conducted on 4-yr-old Q. suber plants. Inocula consisted of two isolates of Py. spiculum from DBR (DO8 and DO36 from Q. suber). For comparison with these, three isolates previously tested on Q. ilex (2) were included: two isolates of Py. spiculum, PA54 (from Q. suber) and PE156 (from Q. ilex), and one isolate of P. cinnamomi, PE90 (from Q. ilex). All these isolates came from Andalucía region, stored at the oomycete collection of the University of Córdoba and showed a 99 to 100% homology with their expected ITS sequences in GenBank (DQ196131 for Py. spiculum and AY943301 for P. cinnamomi). Inocula were prepared by shaking and mixing propagule bearing mycelium produced in carrot broth Petri dishes (20º C, 4 weeks) in sterile water, to produce a concentration of 3×104 oospores×ml-1 (Py. spiculum) or 3×104 chlamydospores×ml-1 (P. cinnamomi), and adding 100 ml of inoculum to each root (2). There were 10 inoculated plants per isolate and 10 non-inoculated control plants. All the plants were waterlogged 2 days per week to favour root infection and maintained in an acclimatised greenhouse (12–28° C). Three months later, the inoculated plants showed symptoms of root necrosis that resulted in foliar wilting, followed occasionally by defoliation. Control plants did not develop foliar symptoms nor root necrosis. Analysis of variance and comparison of means by the Tukey’s test was performed for root necrosis values of inoculated plants, assessed in the 0-4 scale (0 = healthy root, 4 = dead root) used previously (3). Root damage severity exhibited significant differences (P<0.05) in relation to the control plants for all the isolates tested, with isolate PE90 (P. cinnamomi) and isolates PA54, DO8 and DO36 (P. spiculum) all averaging a root necrosis value of 2.5. Isolate PE156 of P. spiculum produced values of root necrosis (1.6 in average) significantly lower (P<0.05) than the rest. This isolate belongs to the low virulence group of P. spiculum described on Q. ilex (2). The inoculated oomycete was always re-isolated from necrotic roots and never from roots of control plants.
    Plant Disease 01/2013; · 2.74 Impact Factor
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    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.
    PLoS Biology 11/2012; 10(11):e1001419. · 12.69 Impact Factor
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    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
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    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
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    3 Biotech. 01/2012;
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    ABSTRACT: Pythium spiculum, a recently described new taxon, has been isolated from declining cork oaks (Quercus suber L.) at Doñana National Park (south-western Spain). The microorganism can infect and cause root disease in Quercus, but currently it is unknown whether its hyphal bodies can germinate and infect host trees. These hyphal bodies, regardless of shape, have been shown to be able to germinate, producing long germ tubes, sometimes ramified. Zoospore production was not recorded, but hyphal bodies are potential host infective structures in dry soil conditions.
    Phytopathologia Mediterranea 12/2011; 50(3):478-481. · 0.79 Impact Factor
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    ABSTRACT: The unhairing step in leather manufacture generates a highly hazardous and alkaline wastewater. This article reports the evaluation of an activated sludge system for the treatment of unhairing wastewater and effluent detoxification, assessed by seed germination tests.The activated sludge system reactor was fed for 112 days with diluted unhairing effluent; the operation strategy included increasing the organic loading rate (OLR) from 0.7 to 1.6 g chemical oxygen demand (COD) L−1 d−1. COD and suspended solids (SS) removal efficiencies were up to 85 and 80%, respectively, for an OLR lower than 1.4 g COD L−1 d−1.Sulphide removal efficiency was ∼90%, as sulphide was oxidized to other species such as sulphate. The biological oxidation of thiosulphates into tetrathionates was also investigated.The effect of untreated and treated unhairing wastewater on seed germination of maize, sorghum, and wheat was examined. Treatment decreased the phytotoxicity of the wastewater. Indeed, germination was inhibited when effluent dilution was lower than 90% of untreated wastewater, whereas a positive effect of treated wastewater was noticed.Phytotoxicity assays showed that biological treatment of unhairing wastewater contributed to a decrease in toxicity of the effluent. © 2010 American Institute of Chemical Engineers Environ Prog, 2011
    Environmental Progress & Sustainable Energy 10/2011; 30(3). · 0.87 Impact Factor
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    Ciencias Marinas 06/2011; 37(2):113-124. · 0.61 Impact Factor
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    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.
    Ciencias Marinas. 01/2011; 37:113–124.
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    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.
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    Plant Pathology 12/2010; 59(6). · 2.73 Impact Factor

Publication Stats

473 Citations
132.47 Total Impact Points

Institutions

  • 2012–2014
    • Université de Neuchâtel
      • Laboratoire de biologie du sol
      Neuenburg, Neuchâtel, Switzerland
  • 2005–2014
    • Haute école de santé Genève
      Genève, Geneva, Switzerland
  • 2012–2013
    • University of Sfax
      • LGEM - Enzyme Engineering and Microbiology Laboratory
      Şafāqis, Şafāqis, Tunisia
  • 2009
    • Manipur University
      Imphal, Manipur, India
  • 2008
    • University of Cordoba (Spain)
      • Department of Agronomy
      Cordoue, Andalusia, Spain
    • Institut National des Sciences et Technologies de la Mer
      Şafāqis, Şafāqis, Tunisia
  • 2007
    • Fernfachhochschule Schweiz
      Zürich, Zurich, Switzerland
  • 2005–2006
    • HES-SO Valais-Wallis
      Valais, Switzerland