References of "Thonart, Philippe"
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See detailPotential use of GFP microbial biosensors for the detection of mixing imperfections and cell viability in bioreactors
Delvigne, Frank ULg; Delafosse, Angélique ULg; Collignon, Marie-Laure ULg et al

Conference (2011, September 25)

The dynamics of microbial stress response in intensive cultivation conditions remains misunderstood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as ... [more ▼]

The dynamics of microbial stress response in intensive cultivation conditions remains misunderstood. In this work, two green fluorescent protein (GFP) transcriptional reporters have been used as biosensors of the heterogeneities generated in a two-compartment scale-down reactor. The stress promoters have been chosen for their responsiveness to carbon limitation corresponding to the global substrate profiles encountered in intensive fed-batch cultures. From our results, it can be concluded that the exposure of microbial cells to substrates heterogeneities tends to decrease the GFP expression level in fed-batch mode. Fluorescence intensities have been monitored at the single cell level by using flow cytometry. During the course of the fed-batch culture, a drop at the level of the intracellular GFP content has been observed for the two scale-down operating conditions and for the two promoters sensitive to substrate limitation (rpoS and csiE). The fluorescence drop can be attributed to the repression of these promoters but also to the release of GFP to the extracellular medium according to the increase of the fluorescence level of the supernatant. This leakage has been observed for all the operating conditions, i.e. the scale-down reactors and the culture operating in the normal mode. Interestingly, GFP leakage is more pronounced in the case of the cultures operated in the normal mode. Indeed, staining by propidium iodide (PI) tends to be more elevated for the microbial cells cultured under the normal mode by comparison with those cultured in scale-down conditions, indicating a higher permeability of the membrane. These results are in accordance with previously published ones (Hewitt and co-workers) suggesting that microbial cells cultivated in heterogeneous bioreactors (scale-down and large-scale bioreactors) exhibits a higher viability level. These results suggest that GFP microbial biosensors could be used to detect simultaneously mixing imperfections and their impact on the viability of microorganisms. [less ▲]

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See detailMICRO-H2 – Microbiological production of hydrogen: study of microalgal and bacterial processes
Calusinska, Magdalena ULg; Joris, Bernard ULg; Wilmotte, Annick ULg et al

Poster (2011, September 07)

The project MICRO-H2 aims to study and exploit the microbial (bacterial and algal) production of hydrogen (H2). In addition to building a competence centre around the H2 production by microorganisms and ... [more ▼]

The project MICRO-H2 aims to study and exploit the microbial (bacterial and algal) production of hydrogen (H2). In addition to building a competence centre around the H2 production by microorganisms and the molecular monitoring of the processes, this project tries to address two main socio-economic issues. First, transport and many economic activities will be based on hydrogen energy in the near future. Secondly, many researches and technology developments deal with renewable resources. Therefore, a new integrated technology for a sustainable development should be promoted. Photofermentation and dark-fermentation are the most promising ways to produce biohydrogen. The main advantage of the first process is the complete conversion of substrate, if any, to hydrogen. However, present H2-production rates by microalgae remain low. Therefore, a better understanding of the microalgal hydrogen metabolism and rate improvements by genetic engineering are needed. On the other hand, dark-fermentation achieves at present far higher H2-production rates, but improvements are expected through monitoring and optimisation of bacterial diversity and activity. The objectives about bacterial H2 production were to increase knowledge, stability potentialities and investigation skills about the consortia of bacteria involved in bioreactors treating wastewater rich in carbohydrates to produce biohydrogen. The project focused mainly on the study of the potentialities of different consortia, with a focus on Clostridium strains. Concerning the microalgal production of H2, the objectives were to increase knowledge on the metabolic interactions that determine H2 evolution at the cellular level and to produce new strains with increased ability for H2 production in the two-stage process. [less ▲]

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See detailMicroorganisms from aphid honeydew attract natural enemies and tending ants
Verheggen, François ULg; Leroy, Pascal; Fischer, Christophe ULg et al

Conference (2011, August)

Aphids are some of the most serious pests of cultivated crops worldwide, causing major yield and economic losses. Previous works have demonstrated ants and natural enemies (including ladybeetles and ... [more ▼]

Aphids are some of the most serious pests of cultivated crops worldwide, causing major yield and economic losses. Previous works have demonstrated ants and natural enemies (including ladybeetles and hoverflies) to be able to use aphid volatile chemicals to locate aphid colonies. Here, we report the first isolation of a bacterium from the pea aphid Acyrthosiphon pisum honeydew, Staphylococcus sciuri, which produces kairomones used by the aphidophagous hoverfly Episyrphus balteatus and the Asian Ladybeetle Harmonia axyridis during their search for prey colonies. Some specific semiochemicals produced by S. sciuri were identified as attractants and ovipositional stimulants. Similarly, we have shown scouts of the aphid tending ant species, Lasius niger, to orientate their foraging behaviour toward an Aphis fabae infested plant and we have demonstrated that the odours released by this aphid honeydew were attractive for ant scouts. Again, bacteria were involved in the production of these honeydew semiochemicals. Interestingly, ant scouts were also able to discriminate honeydew odour from A. fabae (usually attended by L. niger) and A. pisum (unattendedby L. niger). Comparison of the volatile and bacteria composition of both aphid species honeydew were attended. [less ▲]

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See detailEarthworms use odor cues to locate and feed on microorganisms in soil
Zirbes, Lara ULg; Mark, Mescher; Vrancken, Véronique ULg et al

in PLoS ONE (2011), 6(7), 21927

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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 ▲]

Detailed reference viewed: 89 (9 ULg)