38 research outputs found
Charaterization of non-ribosomial lipopeptides as biopesticides
Le premier objectif de ce travail a été d’étudier l’implication des lipopeptides de Bacillus spp. dans la colonisation de la rhizosphère de tomates. Alors que seules les souches produisant de la surfactine sont capables de coloniser un milieu synthétique, toutes les souches testées, colonisent la rhizosphère de tomates avec une plus ou moins bonne efficacité quelque soit leur propriété de production de lipopeptide(s). L’efficacité de la colonisation des racines de tomates est principalement espèce-dépendante. Ce n’est que quand une souche est déjà une bonne colonisatrice que la surfactine semble améliorer cette propriété. Le deuxième objectif a été de tester l’effet des lipopeptides surfactine et mycosubtiline contre le phytopathogène obligatoire de la laitue : Bremia lactucae. À l’échelle du laboratoire, la mycosubtiline à 100 mg/L réduit le pourcentage de plantes infestées de 70 %. La surfactine ne montre aucun effet contre le champignon. Un mélange de mycosubtiline et de surfactine à 50 mg/L chacun diminue le pourcentage de plantes infestées de 65 %. Il semble diminuer le nombre de spores par plante infestée alors que cette propriété n’est pas remarquée avec les autres traitements. L’utilisation de la mycosubtiline dans une serre de culture limite la maladie aux symptômes les moins sévères et protège les plantes saines d’une contamination croisée. L’action des lipopeptides dans la colonisation des racines par Bacillus spp. n’avait jamais été validée in situ. De même, c’est la première fois que l’activité des lipopeptides est testée contre un phytopathogène obligatoire.The first aim of this work was to study the role played by the lipopeptides of Bacillus spp. in the colonization of the tomato rhizosphere. While only the strains producing surfactin are able to colonize a synthetic agar medium, all the strains are able to colonize the rhizosphere of tomatoes with a more or less good efficiency, whatever the lipopeptide(s) they have the capability to produce. The efficiency of the colonization of the tomato rhizosphere is species-dependant. However, surfactine seems to improve the efficiency of only the good colonizing strains. The second aim of this thesis was to test the effect of surfactin and mycosubtilin against a biotrophic parasite of lettuce: Bremia lactucae. Used at 100 mg/L, mycosubtilin reduces the percentage of infested plants of 70 %. Surfactin does not have effect against the fungy. A mixture of mycosubtilin and surfactin at both 50 mg/L decreases the percentage of infested plants of 65 %. This mixture seems to reduce the number of spore per infested plant while this property was not found for the other treatments. The use of mycosubtilin in a greenhouse confines the disease to the lowest classes of severity and protects the healthy plants from a cross contamination.The efficiency of lipopeptides of Bacillus spp. in root colonization by these bacteria was never tested in situ before. Furthermore, this is the first time that the activity of lipopeptides is validated against an obligate phytopathogen
Caractérisation des lipopeptides d'origine non ribosomique comme biopesticides
Le premier objectif de ce travail a été d étudier l implication des lipopeptides de Bacillus spp. dans la colonisation de la rhizosphère de tomates. Alors que seules les souches produisant de la surfactine sont capables de coloniser un milieu synthétique, toutes les souches testées, colonisent la rhizosphère de tomates avec une plus ou moins bonne efficacité quelque soit leur propriété de production de lipopeptide(s). L efficacité de la colonisation des racines de tomates est principalement espèce-dépendante. Ce n est que quand une souche est déjà une bonne colonisatrice que la surfactine semble améliorer cette propriété. Le deuxième objectif a été de tester l effet des lipopeptides surfactine et mycosubtiline contre le phytopathogène obligatoire de la laitue : Bremia lactucae. À l échelle du laboratoire, la mycosubtiline à 100 mg/L réduit le pourcentage de plantes infestées de 70 %. La surfactine ne montre aucun effet contre le champignon. Un mélange de mycosubtiline et de surfactine à 50 mg/L chacun diminue le pourcentage de plantes infestées de 65 %. Il semble diminuer le nombre de spores par plante infestée alors que cette propriété n est pas remarquée avec les autres traitements. L utilisation de la mycosubtiline dans une serre de culture limite la maladie aux symptômes les moins sévères et protège les plantes saines d une contamination croisée. L action des lipopeptides dans la colonisation des racines par Bacillus spp. n avait jamais été validée in situ. De même, c est la première fois que l activité des lipopeptides est testée contre un phytopathogène obligatoire.The first aim of this work was to study the role played by the lipopeptides of Bacillus spp. in the colonization of the tomato rhizosphere. While only the strains producing surfactin are able to colonize a synthetic agar medium, all the strains are able to colonize the rhizosphere of tomatoes with a more or less good efficiency, whatever the lipopeptide(s) they have the capability to produce. The efficiency of the colonization of the tomato rhizosphere is species-dependant. However, surfactine seems to improve the efficiency of only the good colonizing strains. The second aim of this thesis was to test the effect of surfactin and mycosubtilin against a biotrophic parasite of lettuce: Bremia lactucae. Used at 100 mg/L, mycosubtilin reduces the percentage of infested plants of 70 %. Surfactin does not have effect against the fungy. A mixture of mycosubtilin and surfactin at both 50 mg/L decreases the percentage of infested plants of 65 %. This mixture seems to reduce the number of spore per infested plant while this property was not found for the other treatments. The use of mycosubtilin in a greenhouse confines the disease to the lowest classes of severity and protects the healthy plants from a cross contamination.The efficiency of lipopeptides of Bacillus spp. in root colonization by these bacteria was never tested in situ before. Furthermore, this is the first time that the activity of lipopeptides is validated against an obligate phytopathogen.LILLE1-Bib. Electronique (590099901) / SudocSudocFranceF
Les biopesticides, compléments et alternatives aux produits phytosanitaires chimiques (synthèse bibliographique).
peer reviewe
Biopesticides, a complementary and alternative approach to the use of agrochemicals. A review
Peer reviewe
Biofilm formation is determinant in tomato rhizosphere colonization by Bacillus velezensis FZB42
National audienceIn this work, the behavior in tomato rhizosphere of Bacillus velezensis FZB42 was analyzed taking into account the surfactin production, the use of tomato roots exudate as substrates, and the biofilm formation. B. velezensis FZB42 and B. amyloliquefaciens S499 have a similar capability to colonize tomato rhizosphere. Little difference in this colonization was observed with surfactin non producing B. velezensis FZB42 mutant strains. B. velezensis is able to grow in the presence of root exudate and used preferentially sucrose, maltose, glutamic, and malic acids as carbon sources. A mutant enable to produce exopolysaccharide (EPS-) was constructed to demonstrate the main importance of biofilm formation on rhizosphere colonization. This mutant had completely lost its ability to form biofilm whatever the substrate present in the culture medium and was unable to efficiently colonize tomato rhizosphere
Burkholderia genome mining for nonribosomal peptide synthetases reveals a great potential for novel siderophores and lipopeptides synthesis
Burkholderia is an important genus encompassing a variety of species, including pathogenic strains as well as strains that promote plant growth. We have carried out a global strategy, which combined two complementary approaches. The first one is genome guided with deep analysis of genome sequences and the second one is assay guided with experiments to support the predictions obtained in silico. This efficient screening for new secondary metabolites, performed on 48 gapless genomes of Burkholderia species, revealed a total of 161 clusters containing nonribosomal peptide synthetases (NRPSs), with the potential to synthesize at least 11 novel products. Most of them are siderophores or lipopeptides, two classes of products with potential application in biocontrol. The strategy led to the identification, for the first time, of the cluster for cepaciachelin biosynthesis in the genome of Burkholderiaambifaria AMMD and a cluster corresponding to a new malleobactin-like siderophore, called phymabactin, was identified in Burkholderiaphymatum STM815 genome. In both cases, the siderophore was produced when the strain was grown in iron-limited conditions. Elsewhere, the cluster for the antifungal burkholdin was detected in the genome of B.ambifaria AMMD and also Burkholderia sp. KJ006. Burkholderiapseudomallei strains harbor the genetic potential to produce a novel lipopeptide called burkhomycin, containing a peptidyl moiety of 12 monomers. A mixture of lipopeptides produced by Burkholderiarhizoxinica lowered the surface tension of the supernatant from 70 to 27mN center dot m(-1). The production of nonribosomal secondary metabolites seems related to the three phylogenetic groups obtained from 16S rRNA sequences. Moreover, the genome-mining approach gave new insights into the nonribosomal synthesis exemplified by the identification of dual C/E domains in lipopeptide NRPSs, up to now essentially found in Pseudomonas strains
Optimization of an enumeration method to study the efficiency of tomato root colonization by several mutants of Bacillus subtilis having a potential as biopesticide
Optimisation of an enumeration method to study the efficiency of tomato roots colonisation by several mutants of B. subtilis having a potential as biopesticides
In silico genome mining, a new approach to detect novel lipopeptides potentially involved in biological control
Biofilm formation is determinant in tomato rhizosphere colonization by Bacillus velezensis FZB42
In this work, the behavior in tomato rhizosphere of Bacillus velezensis FZB42 was analyzed taking into account the surfactin production, the use of tomato roots exudate as substrates, and the biofilm formation. B. velezensis FZB42 and B. amyloliquefaciens S499 have a similar capability to colonize tomato rhizosphere. Little difference in this colonization was observed with surfactin non producing B. velezensis FZB42 mutant strains. B. velezensis is able to grow in the presence of root exudate and used preferentially sucrose, maltose, glutamic, and malic acids as carbon sources. A mutant enable to produce exopolysaccharide (EPS-) was constructed to demonstrate the main importance of biofilm formation on rhizosphere colonization. This mutant had completely lost its ability to form biofilm whatever the substrate present in the culture medium and was unable to efficiently colonize tomato rhizosphere. © 2017 Springer-Verlag GmbH German