What are the main metabolites responsible for the biocontrol potential of Bacillus strains ?

Poster (2013, February 08)

Study of the induced systemic resistance of plants: molecular aspects of the interaction between plant cells and amphiphilic elicitors produced by non-pathogenic rhizobacteria

Doctoral thesis (2013)

Some non pathogenic rhizobacteria could locally interact with plants, leading to the stimulation of a primed protection state in the host plant. Upon subsequent pathogen attack, this priming state allows ... [more ▼]

Some non pathogenic rhizobacteria could locally interact with plants, leading to the stimulation of a primed protection state in the host plant. Upon subsequent pathogen attack, this priming state allows an accelerated activation of defense responses extending to all organs of the plant. Fundamental as well as applied research about this induced systemic resistance (ISR) has been tremendously boosted in the past decades, driven by its evident potential for biological control of plant diseases in agriculture. However very little information is available about molecular mechanisms governing the recognition by plant cells of ISR-specific elicitors. Various compounds retaining the ability to elicit ISR have been isolated, among which the recently emerged class of biosurfactants. We conducted the present thesis work with the scope to highlight how such amphiphilic compounds are perceived at the plant cell surface to stimulate the systemic plant immune system. In the first part, the strain B. amyloliquefaciens was selected out of other isolates for its technological traits and previously characterized ISR activity. We demonstrated that surfactin is the most competent cyclic lipopeptide (cLP) family produced by this strain to confer ISR on the selected plant model, tobacco. In order to improve our knowledge about the mechanism governing the perception of this biosurfactant at the plant cell surface, we have combined various approaches such as structure/activity (stimulation of the defense-related oxidative burst) relationship, insertion kinetics within membranes of tobacco cultured cells and thermodynamic determination of binding parameters on various model membranes via isothermal titration calorimetry. Our data indicate that surfactin perception relies on a lipid-driven process which is quite uncommon regarding the typical proteic receptor-mediated recognition of molecular patterns governing the plant basal immunity. We then demonstrate that cLPs induce some enrichment or depletion into specific lipid platforms of different proteins. We hypothesize that it may be: (1) the direct consequence of the generation of insertion sites for some proteins in the entire plasma membrane due to specific cLP segregation at lipid phase interfaces; or (2) result from the indirect adjustment of lipid-modifying enzymes activities through an induced rearrangement of the plasma membrane lipid organization. It reinforces the current hypothesis of a role for lipid microdomains-driven lateral compartmentalization in plant cell signaling. The lipid bilayer of target cells could now be considered as the focal point of cLPs perception from where start cellular responses. As they display an original mechanism of action, the class of amphiphilic ISR elicitors to which they belong become more attractive than ever for further development of innovative biopesticides. [less ▲]

Delayed graft function (DGF) does not harm the results of controlled donation-after-cardiovascular death (DCD) in kidney transplantation.

Poster (2013, February 08)

Do Maastricht category III donation after cardiovascular death (DCD) donors experience end-of-life shortening?

Poster (2013, February 08)

Influence of drying and hydrothermal treatments on the denaturation of corn proteins

Poster (2013, February 08)

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several ... [more ▼]

Corn (Zea mays L.) is the most abundant cereal grain produced in the world. It also provides a significant amount of protein in human and animal diets. During drying corn grains undergo several alterations including protein denaturation. A series of studies have been conducted in order to understand mechanisms behind denaturation of corn proteins during drying and heat moisture treatments. Using a laboratory fluidized-bed dryer, a flint corn variety have been dried between 54° and 130°C and subjected to different analyses from a qualitative point of view with a sequential extraction of corn protein fractions and from a quantitative point of view with the modeling of salt-soluble proteins using Promatest assay. Albumin, globulin and zein solubilities dropped significantly when the drying temperature increased. The electrophoretic patterns of zein and glutelin-G1 were not significantly modified, although the solubility of zein was affected by the drying temperature. The analysis of the different protein group solubilities suggested that denaturation mechanisms other than the creation of new disulfide bonds occurred during the drying of corn at high temperature. The study of the effect of heat treatments on the extractability of salt-soluble proteins shows that temperature; moisture content and time of processing greatly influence their kinetic denaturation. Modeling of salt-soluble proteins reveals that the evolution of extractible salt-soluble proteins content of corn kernels during drying at high temperature is more correctly described with a second order kinetic reaction. Investigations continue in order to understand protein denaturation and influence in functional properties and end-use of corn protein-based products. [less ▲]

Viruses and Cancer

Conference (2013, February 08)

Functional screening of a metagenomic library from algal biofilms

in Smagghe, Guy; Boeckx, Pascal; Bossier, Peter (Eds.) et al Communications in Agricultural and Applied Biological Sciences (2013, February 08)

Macroalgae, and particularly their lignin-free polysaccharides, are increasingly used for their gelling and therapeutic properties and for the production of biofuels and renewable chemical compounds. To ... [more ▼]

Macroalgae, and particularly their lignin-free polysaccharides, are increasingly used for their gelling and therapeutic properties and for the production of biofuels and renewable chemical compounds. To extract, hydrolyze and purify this biomass, algae hydrolyzing enzymes are needed. Our work aims to identify and characterize algal biomass hydrolyzing enzymes expressed by microorganisms living on the surface of algae, by functional metagenomics. Therefore, a microbial DNA extraction method was developed to isolate the gDNA from the microorganisms of the brown algae Ascophyllum nodosum and a metagenomic library was constructed in Escherichia coli. The library was screened for diverse enzymatic activities (esterases, xylanases, cellulases, α-amylases, arabinanases, caseinases and β-glucosidases) on agar plates with specific enzymes substrates. Several new microbial enzymes (esterases, β-glucosidases, α-amylases and cellulases) were identified revealing the wealth of our library. Furthermore, those enzymes had less than 50% sequence identity with known protein sequences; meaning that our approach allows to identify new microbial enzymes expressed by uncultured microorganisms. Plate tests for medium-throughput screening of specific enzymes hydrolyzing algal polysaccharides (agarases, carrageenases and alginate lyases) are currently being developed. Our approach will probably allow us to identify new families of those ill-known enzymes, with particular enzymatic activities. [less ▲]

On-line flow cytometry profiling of Escherichia coli stress response

Conference (2013, February 08)

Impact of the depth on bacterial diversity in an agricultural soil

Poster (2013, February 08)

Bacteria are the most abundant and diverse microorganisms in soils. They play an important role in soil formation, contribute to plant nutrition and are involved in various processes in agroecosystems ... [more ▼]

Bacteria are the most abundant and diverse microorganisms in soils. They play an important role in soil formation, contribute to plant nutrition and are involved in various processes in agroecosystems such as nutrient cycling. The aim of this study was to evaluate the impact of the depth on bacterial diversity and quantity in an agricultural soil. Samples was collected on May 2011 and May 2012 at three different depths : 10, 25 and 45 centimeters. The quantity of total bacteria was measured by real time PCR and the analysis of the diversity was performed by the high throughput sequencing technology. Results obtained by these methods show that the biomass and the bacterial quantity and diversity (Shannon index) decrease with the depth, particularly at 45 centimeters. The biomass is, in average, 6.5 fold less important at 45 cm than at 10 cm and the quantity is 17 fold lower at 45 cm than at 10 cm. Our results also indicate that many taxa, such as Betaprotebacteria, Deltaproterobacteria, Gammaproteobacteria, Acidobacteria and Burkholderiales are influenced by the depth. The results will be presented in more details on the poster. [less ▲]

Automatic Aircraft Cargo Load Planning with Pick-up and Delivery

Conference (2013, February 07)

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple ... [more ▼]

This research aims to develop a new mixed integer linear program to solve the containers assignment problem when pickup and deliveries are considered. Given a pool of ULDs and an aircraft with multiple destinations, we want to obtain a loading plan determining at which positions the ULDs must be assigned in order to minimize simultaneous the quantity of fuel consumed and the number of re-handles. The loading plan should also ensure a number of structural, safety and manoeuvrability constraints. The model has been tested on real instances and provides encouraging results. [less ▲]