References of "Thonart, Philippe"
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See detailMicroorganisms from Aphid Honeydew Attract and Enhance the Efficacy of Natural Enemies
Leroy, Pascal ULg; Sabri, Ahmed ULg; Heuskin, Stéphanie ULg et al

in Nature Communications (2011), 2

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their ... [more ▼]

Aphids are one of the most serious pests of crops worldwide, causing major yield and economic losses. To control aphids, natural enemies could be an option but their efficacy is sometimes limited by their dispersal in natural environment. Here we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which acts as a kairomone enhancing the efficiency of aphid natural enemies. Our findings represent the first case of a host-associated bacterium driving prey location and ovipositional preference for the natural enemy. We show that this bacterium has a key role in tritrophic interactions because it is the direct source of volatiles used to locate prey. Some specific semiochemicals produced by S. sciuri were also identified as significant attractants and ovipositional stimulants. The use of this host-associated bacterium could certainly provide a novel approach to control aphids in field and greenhouse systems. [less ▲]

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See detailA semiochemical enhancing the attractiveness of aphidophagous predators in potato crops
Leroy, Pascal ULg; Vandereycken, Axel ULg; Sabri, Ahmed ULg et al

Poster (2011, May 24)

Aphids are major pests of crops worldwide and the use of pesticides has led to resistant populations. The integration of aphid natural enemies in integrated management programs could be an option, but ... [more ▼]

Aphids are major pests of crops worldwide and the use of pesticides has led to resistant populations. The integration of aphid natural enemies in integrated management programs could be an option, but their efficacy is often limited by their quick dispersal from the ecosystem where they are released. Here, using wind-tunnel and field experiments, we have demonstrated that 3-Methyl-2-butenal acts as an efficient attractant and ovipositional stimulant for the hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae), enhancing its efficiency as biological control agent in crop fields. Wind-tunnel assays allowed determining that a minimal dose of 250 µg of 3-Methyl-2-butenal is required to attract the hoverflies over a distance of 2.5 m while a minimal dose of 500 µg is needed to induce the oviposition. Both attraction and oviposition increased proportionally to the tested doses showing that hoverflies are able to regulate their oviposition according to the chemical stimuli from their environment. In field experiments, both Syrphidae and Chrysopidae were strongly attracted by the 3-Methyl-2-butenal at a dose of 10 mg which also induces the oviposition of these two aphid predators in potato crops. This study also highlighted that hoverflies are the most abundant aphid predators found in natural environment. Against aphids, the use of this semiochemical could certainly enhance the efficiency of natural enemies. Furthermore, the use of the chemical cue 3-Methyl-2-butenal could provide a novel approach to control aphids in field and greenhouse systems. [less ▲]

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See detailPotentialités d’application des technologies biologiques pour la depollution des sols en Wallonie
Aldric, Jean-Marc ULg; Druart, P.; Maesen, Philippe ULg et al

in Journal des Ingénieurs (Le) (2011), 132

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See detailEx vivo ruminal cellulosome for by-product biomass conversion
Hissette, Mathias ULg; Destain, Jacqueline ULg; Thewis, André ULg et al

Conference (2011, April 27)

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See detailStudy of viability of Pseudomonas fluorescens BTP1 freeze-dried during storage at 4 and 20°C
Mputu Kanyinda, Jean-Noël ULg; Thonart, Philippe ULg

Poster (2011, April 05)

The drying of bacteria remains a major alternative in order to keep them long term. After centrifugation, the bacterial pellet of Pseudomonas fluorescens BTP1 was divided in two fractions one with and one ... [more ▼]

The drying of bacteria remains a major alternative in order to keep them long term. After centrifugation, the bacterial pellet of Pseudomonas fluorescens BTP1 was divided in two fractions one with and one without cryoprotectants (2% glycerol and 5% maltodextrine) and freeze-dried. After freeze drying, powders were sealed in aluminium bag under vacuum and storage at 4 or 20°C. The storage stability of freeze-dried powders was studied by parameters such as loss of viability on the Plate Count Agar (PCA) (e.g. Concentration of Cells with glycerol (PG) at CFU/g before storage 109 and after 7 month, 108 at 4°C and 107 at 20°C) and evolution in membrane composition by measuring the ratio of unsaturated/saturated fatty acid. These ratios decrease in function of time (e.g. at 4°C the ratios of C18:3 and C18:2 by C16:0 decreases respectively of 0,013 to 0,001 and 0,05 to 0,03 after 60 days of storage). Viability (%) and concentration (CFU/g) of bacterial during storage at 4 or 20°C with aw = 0,32 was determined using a procedure published by (Kurtmann et al., 2009). In the present study, flow cytometric analysis was applied to evaluate the state in which are the cells at the end of storage time. Furthermore, we compared result the survival of bacteria as obtained by plate count with the flow cytometric analysis results. [less ▲]

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See detailThe semiochemically mediated interactions between bacteria and insects
Leroy, Pascal ULg; Sabri, Ahmed ULg; Verheggen, François ULg et al

in Chemoecology (2011), 21

In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile ... [more ▼]

In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically-mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests. [less ▲]

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See detailThe role of surfactins in plant immunization by Bacilli
Cawoy, Hélène ULg; Henry, Guillaume ULg; Jourdan, Emmanuel ULg et al

Conference (2011, April)

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See detailEffect of different protectants on viability of thermotolerant acetic acid bacterium Acetobacter sengalenisis
Shafiei, Rasoul ULg; Thonart, Philippe ULg

in Annual Confernace of the Association for general and applied microbiology (VAAM) (2011, April)

Production of vinegar at high temperature (>37° C) needs special processes and equipments; one of the key elements in the process, is the accessibility of active and stable starters. In this study the ... [more ▼]

Production of vinegar at high temperature (>37° C) needs special processes and equipments; one of the key elements in the process, is the accessibility of active and stable starters. In this study the influences of different cryo-protective agents on some steps (freezing, drying and storage) of starter production were investigated. To achieve this goal, Acetobacter senegalensis, was used as a thermotolerant acetic acid bacterium. Glucose was used as carbon source in fermentor to produce biomass. Different cryo-protectants (manitol (20%), glycerol (3%), sucrose (10%), trehalose (5%), glutamate (3%), maltodextrin (10%), skimmed milk (10%) and spent growth medium) were added to washed and unwashed biomass. The lyophilized cells (92-93% water content) were stored in darkness under different temperatures (-20° C, +4° C and 35° C). The viability of cells after rehydration, activity of glucose dehydrogenase, gluconate dehydrogenase and soluble protein contents were determined up to 6 months. According to the results, washing of cells by tap water has no effect on viability of cells during freezing and more than 97% of cells are alive in all treatments. After lyophilization, unwashed cells showed higher viability in all treatments in comparison to washed cells. On the basis of residual viable cells, manitol, maltodextrin, and spent growth medium showed the highest protective effects (92.3%, 88.2% and 82.1% survival, respectively) on cells during drying process whereas glycerol had the lowest protective effect on viability (15.4% survival). During storage of lyophilized cells at 35° C, 100% of cells are dead in all treatments after 15 days. Unwashed cells treated with manitol, maltodextrin and spent growth medium showed 79.2%, 68.3% and 62.7% viability, respectively after keeping at 4°C for 6 months. There is direct relationship between the soluble protein contents of cells and storage temperature. Cells stored at -20° C showed highest soluble protein contents after 6 months of storage while the lowest amount of soluble protein contents was detected in cells stored at 35° C. On the other hand, glucose dehydrogenase and gluconate dehydrogenase activities decreased during storage of cells at 4°C, whereas more than 90% of the enzymes activity remained during storage of different cells at -20° C, so it can be assumed that higher temperature can inactivate cell proteins. In conclusion, lyophilization of Acetobacter senegalensis by the mentioned methods can provide a promising and economic tool for production of stable and active vinegar starters. [less ▲]

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See detailMicroorganisms from aphids attract hoverflies and enhance their efficacy
Leroy, Pascal ULg; Sabri, Ahmed ULg; Heuskin, Stéphanie ULg et al

Poster (2011, March 05)

Aphids are some of the most serious pests of crops worldwide, causing major yield and economic losses. They damage plants by feeding on the phloem sap, excreting copious amounts of honeydew and, in some ... [more ▼]

Aphids are some of the most serious pests of crops worldwide, causing major yield and economic losses. They damage plants by feeding on the phloem sap, excreting copious amounts of honeydew and, in some cases, vectoring plant diseases. Here, we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which is involved in the release of semiochemicals acting as a kairomone for aphid natural enemies. These semiochemicals were identified by Solid-Phase Microextraction (SPME) and Gas Chromatography-Mass Spectrometry (GC-MS). Our results show that this bacterium plays a key role in the interactions between aphids and natural enemies because it is the direct source of volatiles used by the aphidophagous hoverfly Episyrphus balteatus (De Geer) (Diptera: Syrphidae) to locate its aphid prey. Through wind-tunnel experiments, some specific semiochemicals produced by S. sciuri were identified as significant attractants and ovipositional stimulants. Also, assays under greenhouses and in potato fields have demonstrated that a culture medium containing the bacterium S. sciuri strongly attracts and induces the oviposition of hoverflies, enhancing their efficiency as biological control agents. The use of this no pathogenic bacterium could provide a very novel approach towards enhancing the efficacy of biological control agents to control aphids in field crops and greenhouse systems. [less ▲]

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See detailIn vitro culture of the parasitic wasp Aphidius ervi: Sweet dream or Reality
Sabri, Ahmed ULg; Leroy, Pascal ULg; Haubruge, Eric ULg et al

Poster (2011, March 03)

Aphidius ervi is an entomophagous parasitoid and represents an effective parasitoid of several aphid species that cause great damages in agriculture. Several investigations, for its in vitro mass ... [more ▼]

Aphidius ervi is an entomophagous parasitoid and represents an effective parasitoid of several aphid species that cause great damages in agriculture. Several investigations, for its in vitro mass production, have achieved a limited success and suggest that in vitro culture of this valuable biological control agent is rather closer to a dream than reality. Our work provides a chronological study of A. ervi development, from the oviposition until hatching of the first instar larva, in the body of the pea aphid Acyrthosiphon pisum. We show that this parasitoid has some characteristics in its embryological development that are rather complex and different from most other reported insects, which can be phylogenetically very close. Some of these characteristics concern extraembryonic membranes and could be among the causes of the limited success achieved in the in vitro culture. [less ▲]

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See detailBiomass production and small-scale testing of freeze-dried lactic acid bacteria starter strains for cassava fermentations
Edward, V.; Huch, M.; Dortu, C. et al

in Food Control (2011), 22(3-4), 389395

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See detailAphid-host plant interactions: Does aphid honeydew exactly reflect the host plant amino acid composition?
Leroy, Pascal ULg; Wathelet, Bernard ULg; Sabri, Ahmed ULg et al

in Arthropod-Plant Interactions (2011), 5

Plants provide aphids with unbalanced and low concentrations of amino acids. Likely, intracellular symbionts improve the aphid nutrition by participating to the synthesis of essential amino acids. To ... [more ▼]

Plants provide aphids with unbalanced and low concentrations of amino acids. Likely, intracellular symbionts improve the aphid nutrition by participating to the synthesis of essential amino acids. To compare the aphid amino acid uptakes from the host plant and the aphids amino acid excretion into the honeydew, host plant exudates (phloem + xylem) from infested and uninfested Vicia faba L. plants were compared to the honeydew produced by two aphid species (Acyrthosiphon pisum Harris and Megoura viciae Buckton) feeding on V. faba. Our results show that an aphid infestation modifies the amino acid composition of the infested broad bean plant since the global concentration of amino acids significantly increased into the host plant in response to aphid infestations. Specifically, the concentrations of two amino acids glutamine and asparagine were strongly enhanced. The amino acid profiles from honeydews were similar for the two aphid species, but the concentrations found into the honeydews were generally lower than those measured in the exudates of infested plants (aphids uptakes). This work also highlights that aphids take large amounts of amino acids into the host plant, especially glutamine and asparagine which are converted into glutamic and aspartic acids but also into other essential amino acids. The amino acid profiles differed between the host plant exudates and the aphid excretion product. Finally, this study highlights that the pea aphid - a “specialist” for the V. faba host plant - induced more important modifications into the host plant amino acid composition than the “generalist” aphid M. viciae. [less ▲]

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See detailIn vitro antagonistic activity evaluation of Lactic Acid Bacteria (LAB) combined with cellulase enzyme against Campylobacter jejuni growth in co-culture
Dubois Dauphin, Robin ULg; vandeplas, Sabrina; Didderen, Isabelle et al

in Journal of Microbiology and Biotechnology (2011), 21(1), 62-70

The antibacterial effects of nine Lactic Acid Bacteria (LAB) on Campylobacter jejuni were investigated using agar gel diffusion and co-culture assay. Inhibition potential was not the same between both ... [more ▼]

The antibacterial effects of nine Lactic Acid Bacteria (LAB) on Campylobacter jejuni were investigated using agar gel diffusion and co-culture assay. Inhibition potential was not the same between both techniques. Only two LAB, Lb. pentosus CWBI B78 and E. faecium THT, showed an anti-campylobacter activity in co-culture assay in using dehydrated poultry excreta mixed with ground straw (DPE/GS) as the only growth substrate source. It was observed that the complementation with Cellulase A complex (Beldem S.A.) of this medium enhanced antimicrobial effect of both bacteria. The co-culture medium acidification was correlated with the concentration in supplemented enzyme. The antibacterial effect was characterized by the production of lactic acid by the homofermentative E. faecium THT and the lactic and acetic acids production by the heterofermentative Lb. pentosus CWBI B78. The antagonistic properties from bacteria-enzyme cooperation could reduce the prevalence of Campylobacter consequently the risk of human infection. [less ▲]

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