The Experts below are selected from a list of 1056 Experts worldwide ranked by ideXlab platform
Frederic Francis - One of the best experts on this subject based on the ideXlab platform.
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Histopathological effects of Aspergillus clavatus (Ascomycota: Trichocomaceae) on larvae of the southern house mosquito, Culex quinquefasciatus (Diptera: Culicidae)
Fungal biology, 2016Co-Authors: Thomas Bawin, Fawrou Seye, Jean-yves Zimmer, Mady Ndiaye, Frank Delvigne, Fara Nantenaina Raharimalala, Slimane Boukraa, Philippe Compère, Frederic FrancisAbstract:Aspergillus clavatus (Ascomycota: Trichocomaceae) was previously found to be an opportunistic pathogen of mosquitoes (Diptera: Culicidae). In the present study, the mechanism leading to its insecticidal activity was investigated regarding histological damages on Culex quinquefasciatus larvae exposed to A. clavatus spores. Multiple concentration assays using spore suspensions (0.5-2.5 × 10(8) spores ml(-1)) revealed 17.0-74.3 % corrected mortalities after 48 h exposure. Heat-deactivated spores induced a lower mortality compared to nonheated spores suggesting that insecticidal effects are actively exerted. Spore-treated and untreated larvae were prepared for light microscopy as well as for scanning and transmission electron microscopy. Spores failed to adhere to the external body surface (except the mouth parts) of these aquatic immature stages but progressively filled the digestive tract where their metabolism seemed to activate. In parallel, the internal tissues of the larvae, i.e. the midgut wall, the skeletal muscles, and the cuticle-secreting epidermis, were progressively destroyed between 8 and 24 h of exposure. These observations suggest that toxins secreted by active germinating spores of A. clavatus in the digestive tract altered the larval tissues, leading to their necrosis and causing larval death. Fungal proliferation and sporulation then occurred during a saprophytic phase. A. clavatus enzymes or toxins responsible for these pathogenic effects need to be identified in further studies before any use of this fungus in mosquito control.
Mohamed Hajji - One of the best experts on this subject based on the ideXlab platform.
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gene cloning and expression of a detergent stable alkaline protease from Aspergillus clavatus es1
Process Biochemistry, 2010Co-Authors: Mohamed Hajji, Noomen Hmidet, Kemel Jellouli, Tatiana Vallaeys, Moncef Nasri, Alya SellamikamounAbstract:Abstract The genes, cDNA alpES1 and alpES1, encoding Aspergillus clavatus ES1 alkaline protease were amplified from complementary DNA (cDNA) and genomic DNA, respectively, cloned in pCR®II-TOPO plasmid and then sequenced. Sequence analysis of the cDNA alpES1 gene revealed an open reading frame (ORF) of 1212 bp encoding a pre–pro-protein of 403 amino acid residues consisting of a 21-aa signal peptide, a 100-aa pro-peptide and a 282-aa mature protein with a calculated molecular weight of 28.5 kDa. Compared to the cDNA alpES1 gene, the alpES1 gene contained three introns, which had 53, 57 and 54 bp, respectively. The cDNA alpES1 gene was then sub-cloned in pET-30b(+) and expressed in Escherichia coli BL21 (λDE3). The purified recombinant protease had a molecular weight of about 32 kDa estimated by SDS-PAGE. Kinetic parameters, Km and kcat values of the recombinant AlpES1 for casein, were 0.23 mM and 12.38 min−1, respectively. The catalytic efficiency (kcat/Km) was 53.82 min−1 mM−1.
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a highly thermostable antimicrobial peptide from Aspergillus clavatus es1 biochemical and molecular characterization
Journal of Industrial Microbiology & Biotechnology, 2010Co-Authors: Mohamed Hajji, Noomen Hmidet, Kemel Jellouli, Alya Sellamikamoun, Rafik Balti, Moncef NasriAbstract:Antimicrobial peptides (AMPs) are extremely attractive candidates as therapeutic agents due to their wide spectrum of antimicrobial activity and mechanism of action, which differs from that of small-molecule antibiotics. In this study, a 6.0-kDa antimicrobial peptide from Aspergillus clavatus ES1, designated as AcAMP, was isolated by a one-step heat treatment. AcAMP was sensitive to proteolytic enzymes, stable between pH 5.0 and 10.0, and heat resistant (15 min at 100 degrees C). The acamp gene encoding AcAMP peptide was isolated by reverse-transcriptase polymerase chain reaction (RT-PCR) and cloned in pCRII-TOPO vector. Sequence analysis of the complementary DNA (cDNA) acamp gene revealed an open reading frame of 282 bp encoding a peptide of 94 amino acid residues consisting of a 21-aa signal peptide, a 22-aa pro-peptide, and a 51-aa mature peptide. The deduced amino acid sequence showed high identity with other ascomycete antifungal peptides. AcAMP belongs to the group of small, cysteine-rich, basic proteins with antimicrobial activity. In addition to its antifungal activity, AcAMP is the first fungal peptide exhibiting antibacterial activity against several Gram-positive and Gram-negative bacteria. Based on all these features, AcAMP can be considered as a promising new member of the restraint family of ascomycete antimicrobial peptides that might be used in biological control of plant diseases and also for potential applications in food preservation.
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Optimization of alkaline protease production by Aspergillus clavatus ES1 in Mirabilis jalapa tuber powder using statistical experimental design
Applied Microbiology and Biotechnology, 2008Co-Authors: Mohamed Hajji, Neji Gharsallah, Ahmed Rebai, Moncef NasriAbstract:Medium composition and culture conditions for the bleaching stable alkaline protease production by Aspergillus clavatus ES1 were optimized. Two statistical methods were used. Plackett–Burman design was applied to find the key ingredients and conditions for the best yield. Response surface methodology (RSM) including full factorial design was used to determine the optimal concentrations and conditions. Results indicated that Mirabilis jalapa tubers powder (MJTP), culture temperature, and initial medium pH had significant effects on the production. Under the proposed optimized conditions, the protease experimental yield (770.66 U/ml) closely matched the yield predicted by the statistical model (749.94 U/ml) with R ^2 = 0.98. The optimum operating conditions obtained from the RSM were MJTP concentration of 10 g/l, pH 8.0, and temperature of 30 °C, Sardinella heads and viscera flour (SHVF) and other salts were used at low level. The medium optimization contributed an about 14.0-fold higher yield than that of the unoptimized medium (starch 5 g/l, yeast extract 2 g/l, temperature 30 °C, and pH 6.0; 56 U/ml). More interestingly, the optimization was carried out with the by-product sources, which may result in cost–effective production of alkaline protease by the strain.
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purification and characterization of an alkaline serine protease produced by a new isolated Aspergillus clavatus es1
Process Biochemistry, 2007Co-Authors: Mohamed Hajji, Moncef Nasri, Safia Kanoun, Neji GharsallahAbstract:Abstract An extracellular bleach stable protease from the fungus Aspergillus clavatus ES1, isolated from wastewater, was purified and characterized. The protease of ES1 strain was purified to homogeneity using acetone precipitation, Sephadex G-100 gel filtration and CM-Sepharose ion exchange chromatography, with a 7.5-fold increase in specific activity and 29% recovery. The molecular mass was estimated to be 32 kDa on SDS-PAGE. The optimum pH and temperature for the proteolytic activity were pH 8.5 and 50 °C, respectively. The enzyme was stable in the pH range of 7.0–9.0. The protease was activated by divalent cations such as Ca2+ and Mg2+. The alkaline protease showed extreme stability towards non-ionic surfactants (5% Tween 80 and 5% Triton X-100). In addition, the enzyme was relatively stable towards oxidizing agents, retaining more than 71 and 53% of its initial activity after 1 h incubation in the presence of 1 and 2% (w/v) sodium perborate, respectively. The N-terminal sequence of the first 15 amino acids of the purified alkaline protease of A. clavatus ES1 showed high similarity with other fungal alkaline proteases. The activity was totally lost in the presence of PMSF, suggesting that the purified enzyme is a serine-protease.
Moncef Nasri - One of the best experts on this subject based on the ideXlab platform.
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gene cloning and expression of a detergent stable alkaline protease from Aspergillus clavatus es1
Process Biochemistry, 2010Co-Authors: Mohamed Hajji, Noomen Hmidet, Kemel Jellouli, Tatiana Vallaeys, Moncef Nasri, Alya SellamikamounAbstract:Abstract The genes, cDNA alpES1 and alpES1, encoding Aspergillus clavatus ES1 alkaline protease were amplified from complementary DNA (cDNA) and genomic DNA, respectively, cloned in pCR®II-TOPO plasmid and then sequenced. Sequence analysis of the cDNA alpES1 gene revealed an open reading frame (ORF) of 1212 bp encoding a pre–pro-protein of 403 amino acid residues consisting of a 21-aa signal peptide, a 100-aa pro-peptide and a 282-aa mature protein with a calculated molecular weight of 28.5 kDa. Compared to the cDNA alpES1 gene, the alpES1 gene contained three introns, which had 53, 57 and 54 bp, respectively. The cDNA alpES1 gene was then sub-cloned in pET-30b(+) and expressed in Escherichia coli BL21 (λDE3). The purified recombinant protease had a molecular weight of about 32 kDa estimated by SDS-PAGE. Kinetic parameters, Km and kcat values of the recombinant AlpES1 for casein, were 0.23 mM and 12.38 min−1, respectively. The catalytic efficiency (kcat/Km) was 53.82 min−1 mM−1.
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a highly thermostable antimicrobial peptide from Aspergillus clavatus es1 biochemical and molecular characterization
Journal of Industrial Microbiology & Biotechnology, 2010Co-Authors: Mohamed Hajji, Noomen Hmidet, Kemel Jellouli, Alya Sellamikamoun, Rafik Balti, Moncef NasriAbstract:Antimicrobial peptides (AMPs) are extremely attractive candidates as therapeutic agents due to their wide spectrum of antimicrobial activity and mechanism of action, which differs from that of small-molecule antibiotics. In this study, a 6.0-kDa antimicrobial peptide from Aspergillus clavatus ES1, designated as AcAMP, was isolated by a one-step heat treatment. AcAMP was sensitive to proteolytic enzymes, stable between pH 5.0 and 10.0, and heat resistant (15 min at 100 degrees C). The acamp gene encoding AcAMP peptide was isolated by reverse-transcriptase polymerase chain reaction (RT-PCR) and cloned in pCRII-TOPO vector. Sequence analysis of the complementary DNA (cDNA) acamp gene revealed an open reading frame of 282 bp encoding a peptide of 94 amino acid residues consisting of a 21-aa signal peptide, a 22-aa pro-peptide, and a 51-aa mature peptide. The deduced amino acid sequence showed high identity with other ascomycete antifungal peptides. AcAMP belongs to the group of small, cysteine-rich, basic proteins with antimicrobial activity. In addition to its antifungal activity, AcAMP is the first fungal peptide exhibiting antibacterial activity against several Gram-positive and Gram-negative bacteria. Based on all these features, AcAMP can be considered as a promising new member of the restraint family of ascomycete antimicrobial peptides that might be used in biological control of plant diseases and also for potential applications in food preservation.
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Optimization of alkaline protease production by Aspergillus clavatus ES1 in Mirabilis jalapa tuber powder using statistical experimental design
Applied Microbiology and Biotechnology, 2008Co-Authors: Mohamed Hajji, Neji Gharsallah, Ahmed Rebai, Moncef NasriAbstract:Medium composition and culture conditions for the bleaching stable alkaline protease production by Aspergillus clavatus ES1 were optimized. Two statistical methods were used. Plackett–Burman design was applied to find the key ingredients and conditions for the best yield. Response surface methodology (RSM) including full factorial design was used to determine the optimal concentrations and conditions. Results indicated that Mirabilis jalapa tubers powder (MJTP), culture temperature, and initial medium pH had significant effects on the production. Under the proposed optimized conditions, the protease experimental yield (770.66 U/ml) closely matched the yield predicted by the statistical model (749.94 U/ml) with R ^2 = 0.98. The optimum operating conditions obtained from the RSM were MJTP concentration of 10 g/l, pH 8.0, and temperature of 30 °C, Sardinella heads and viscera flour (SHVF) and other salts were used at low level. The medium optimization contributed an about 14.0-fold higher yield than that of the unoptimized medium (starch 5 g/l, yeast extract 2 g/l, temperature 30 °C, and pH 6.0; 56 U/ml). More interestingly, the optimization was carried out with the by-product sources, which may result in cost–effective production of alkaline protease by the strain.
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purification and characterization of an alkaline serine protease produced by a new isolated Aspergillus clavatus es1
Process Biochemistry, 2007Co-Authors: Mohamed Hajji, Moncef Nasri, Safia Kanoun, Neji GharsallahAbstract:Abstract An extracellular bleach stable protease from the fungus Aspergillus clavatus ES1, isolated from wastewater, was purified and characterized. The protease of ES1 strain was purified to homogeneity using acetone precipitation, Sephadex G-100 gel filtration and CM-Sepharose ion exchange chromatography, with a 7.5-fold increase in specific activity and 29% recovery. The molecular mass was estimated to be 32 kDa on SDS-PAGE. The optimum pH and temperature for the proteolytic activity were pH 8.5 and 50 °C, respectively. The enzyme was stable in the pH range of 7.0–9.0. The protease was activated by divalent cations such as Ca2+ and Mg2+. The alkaline protease showed extreme stability towards non-ionic surfactants (5% Tween 80 and 5% Triton X-100). In addition, the enzyme was relatively stable towards oxidizing agents, retaining more than 71 and 53% of its initial activity after 1 h incubation in the presence of 1 and 2% (w/v) sodium perborate, respectively. The N-terminal sequence of the first 15 amino acids of the purified alkaline protease of A. clavatus ES1 showed high similarity with other fungal alkaline proteases. The activity was totally lost in the presence of PMSF, suggesting that the purified enzyme is a serine-protease.
Francis Frédéric - One of the best experts on this subject based on the ideXlab platform.
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Histopathological effects of Aspergillus clavatus (Ascomycota: Trichocomaceae) on larvae of the southern house mosquito, Culex quinquefasciatus (Diptera: Culicidae)
2016Co-Authors: Bawin Thomas, Seye Fawrou, Boukraa Slimane, Zimmer Jean-yves, Ndiaye Mady, Delvigne Frank, Raharimalala, Fara Nantenaina, Compère Philippe, Francis FrédéricAbstract:Aspergillus clavatus (Ascomycota: Trichocomaceae) was previously found to be an opportunistic pathogen of mosquitoes (Diptera: Culicidae). In the present study, the mechanism leading to its insecticidal activity was investigated regarding histological damages on Culex quinquefasciatus larvae exposed to A. clavatus spores. Multiple concentration assays using spore suspensions (0.5 x 10^8 to 2.5 x 10^8 spores/ml) revealed 17.0% to 74.3% corrected mortalities after 48 h exposure. Heat-deactivated spores induced a lower mortality compared to non-heated spores suggesting that insecticidal effects are actively exerted. Spore-treated and untreated larvae were prepared for light microscopy as well as for scanning and transmission electron microscopy. Spores failed to adhere to the external body surface (except the mouth parts) of these aquatic immature stages but progressively filled the digestive tract where their metabolism seemed to activate. In parallel, the internal tissues of the larvae, i.e. the midgut wall, the skeletal muscles, and the cuticle-secreting epidermis, were progressively destroyed between 8 and 24 h of exposure. These observations suggest that toxins secreted by active germinating spores of A. clavatus in the digestive tract altered the larval tissues, leading to their necrosis and causing larval death. Fungal proliferation and sporulation then occurred during a saprophytic phase. A. clavatus enzymes or toxins responsible for these pathogenic effects need to be identified in further studies before any use of this fungus in mosquito control.Peer reviewe
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Pathogenicity of Aspergillus clavatus produced in a fungal biofilm bioreactor toward Culex quinquefasciatus (Diptera: Culicidae)
'Pesticide Science Society of Japan', 2014Co-Authors: Seye Fawrou, Bawin Thomas, Boukraa Slimane, Zimmer Jean-yves, Ndiaye Mady, Delvigne Frank, Francis FrédéricAbstract:peer reviewedaudience: researcher, professional, studentMany entomopathogenic fungi have been demonstrated to be potential agents for efficiently controlling mosquito populations. In the present study, we investigated a bioreactor system to produce metabolites and conidia by combining technological advantages of submerged and solid-state fermentations. The efficiency of fungal products was tested toward mosquitoes. Aspergillus clavatus (Eurotiales: Trichocomaceae) was grown by semi-solid-state fermentation in a bioreactor for up to 7 days. Depending on conidial doses (2.5×10^7, 5×10^7, 7.5×10^7, 10×10^7 and 12.5×10^7 conidia/mL), mortality ranged from 37.2±15.0 to 86.3±5.0% toward larvae and from 35.8±2.0 to 85.2±1.5% toward adults. The metabolites (10, 20, 40, 60, 80 and 100% v/v) yielded mortality from 23.7±15.0 to 100.0±0.1% toward larvae, and two sprayed volumes (5 and 10 mL) reached 45.5±1.4 and 75.6±2.6% mortality, respectively, toward adults
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Pathogenicity of Aspergillus clavatus produced in a fungal biofilm bioreactor toward Culex quinquefasciatus (Diptera: Culicidae)
2014Co-Authors: Seye Fawrou(*), Boukraa Slimane, Zimmer Jean-yves, Ndiaye Mady, Delvigne Frank, Bawin Thomas(*), Francis FrédéricAbstract:Many entomopathogenic fungi have been demonstrated to be potential agents for efficiently controlling mosquito populations. In the present study, we investigated a bioreactor system to produce metabolites and conidia by combining technological advantages of submerged and solid-state fermentations. The efficiency of fungal products was tested toward mosquitoes. Aspergillus clavatus (Eurotiales: Trichocomaceae) was grown by semi-solid-state fermentation in a bioreactor for up to 7 days. Depending on conidial doses (2.5×10^7, 5×10^7, 7.5×10^7, 10×10^7 and 12.5×10^7 conidia/mL), mortality ranged from 37.2±15.0 to 86.3±5.0% toward larvae and from 35.8±2.0 to 85.2±1.5% toward adults. The metabolites (10, 20, 40, 60, 80 and 100% v/v) yielded mortality from 23.7±15.0 to 100.0±0.1% toward larvae, and two sprayed volumes (5 and 10 mL) reached 45.5±1.4 and 75.6±2.6% mortality, respectively, toward adults.Peer reviewe
Thomas Bawin - One of the best experts on this subject based on the ideXlab platform.
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Histopathological effects of Aspergillus clavatus (Ascomycota: Trichocomaceae) on larvae of the southern house mosquito, Culex quinquefasciatus (Diptera: Culicidae)
Fungal biology, 2016Co-Authors: Thomas Bawin, Fawrou Seye, Jean-yves Zimmer, Mady Ndiaye, Frank Delvigne, Fara Nantenaina Raharimalala, Slimane Boukraa, Philippe Compère, Frederic FrancisAbstract:Aspergillus clavatus (Ascomycota: Trichocomaceae) was previously found to be an opportunistic pathogen of mosquitoes (Diptera: Culicidae). In the present study, the mechanism leading to its insecticidal activity was investigated regarding histological damages on Culex quinquefasciatus larvae exposed to A. clavatus spores. Multiple concentration assays using spore suspensions (0.5-2.5 × 10(8) spores ml(-1)) revealed 17.0-74.3 % corrected mortalities after 48 h exposure. Heat-deactivated spores induced a lower mortality compared to nonheated spores suggesting that insecticidal effects are actively exerted. Spore-treated and untreated larvae were prepared for light microscopy as well as for scanning and transmission electron microscopy. Spores failed to adhere to the external body surface (except the mouth parts) of these aquatic immature stages but progressively filled the digestive tract where their metabolism seemed to activate. In parallel, the internal tissues of the larvae, i.e. the midgut wall, the skeletal muscles, and the cuticle-secreting epidermis, were progressively destroyed between 8 and 24 h of exposure. These observations suggest that toxins secreted by active germinating spores of A. clavatus in the digestive tract altered the larval tissues, leading to their necrosis and causing larval death. Fungal proliferation and sporulation then occurred during a saprophytic phase. A. clavatus enzymes or toxins responsible for these pathogenic effects need to be identified in further studies before any use of this fungus in mosquito control.
