The lipoxygenase pathway as defence mechanism against fungal disease specifically stimulated in tomato plants by a non-pathogenic Pseudomonas putida

Poster (2006, May 17)

Role of lipopeptides in the biological control activity of Bacillus subtilis

Conference (2006)

Valorisation des feuilles de betteraves à travers la production de molécules à notes vertes.

Report (2006)

Production and down-stream processing of an extracellular lipase from the yeast Yarrowia lipolytica

in Enzyme & Microbial Technology (2006), 38(6), 756-759

Lipase constitutes an interesting class of enzyme with many biotechnological applications. However, the development of a fruitful process must be set up to obtained a product compatible with the ... [more ▼]

Lipase constitutes an interesting class of enzyme with many biotechnological applications. However, the development of a fruitful process must be set up to obtained a product compatible with the industrial and commercial needs. Here, we report the development of such a process for the extracellular lipase secreted by the yeast Yarrowia lipolytica. The enzyme production, carried out in a 2000 L bioreactor, led to a lipase activity of approximately 1100 U mL(-1) after 53 h of fermentation. The post-culture treatment, consisting of a centrifugation, a filtration and an ultra-filtration steps, led to 15-fold volume reduction and a 8-fold increased of the lipase activity. Finally, addition of 12% of milk powder and 3% of gum arabic before spray-drying dehydration led to a stable powder with a lipolytic activity of 37,500 U g D.W.(-1). (c) 2005 Elsevier Inc. All rights reserved. [less ▲]

Resistance induced in plants by non-pathogenic microorganisms: elicitation and defense responses

in Floriculture, Ornamental and Plant Biotechnology: advances and topical issues (2006)

Plants have evolved a number of inducible defense mechanisms against pathogen attacks. Recognition of certain non-pathogenic rhizobacteria can trigger a systemic resistance reaction that renders the host ... [more ▼]

Plants have evolved a number of inducible defense mechanisms against pathogen attacks. Recognition of certain non-pathogenic rhizobacteria can trigger a systemic resistance reaction that renders the host less susceptible to subsequent infection by a virulent agent. Since this induced systemic resistance (ISR) is long-lasting and not conducive for development of pathogen resistance, disease control strategies based on this phenomenon are promising both for greenhouse cultures and under field conditions. The list of beneficial rhizobacteria reported to induce ISR is growing rapidly. Data compiled here also show that ISR may occur in various dicotyledonous and monocotyledonous plants and can be effective against a wide range of pathogens. This review emphasizes the molecular aspects of this three-step process involving sequentially i) the perception by plant cells of elicitors produced by the inducing agents that initiates the phenomenon, ii) signal transduction that is needed to propagate the induced state systemically through the plant and iii) expression of defense mechanisms sensu stricto that limit or inhibit pathogen penetration into the host tissues. The current state of knowledge about rhizobacteria-stimulated ISR is discussed in parallel with the more wellcharacterized systemic acquired resistance induced by incompatible pathogens. [less ▲]

Systemic resistance induced by Pseudomonas putida BTP1: elicitation and defense response in the host plant

Poster (2005, December)

Mycosubtilin overproduction by Bacillus subtilis BBG100 enhances the organism's antagonistic and biocontrol activities

in Applied and Environmental Microbiology (2005), 71(8), 4577-4584

A Bacillus subtilis derivative was obtained from strain ATCC 6633 by replacement of the native promoter (if he mycosubtilin operon by a constitutive promoter originating from the replication gene repU of ... [more ▼]

A Bacillus subtilis derivative was obtained from strain ATCC 6633 by replacement of the native promoter (if he mycosubtilin operon by a constitutive promoter originating from the replication gene repU of the Staphylococcus aureus plasmid pUB110. The recombinant strain, designated BBG100, produced up to 15-fold more mycosubtilin than the wild type produced. The overproducing phenotype was related to enhancement of the antagonistic activities against several yeasts and pathogenic fungi. Hemolytic activities were also clearly increased in the modified strain. Mass spectrometry analyses of enriched mycosubtilin extracts showed similar patterns of lipopeptides for BBG100 and the wild type. Interestingly, these analyses also revealed a new form of mycosubtilin which was more easily detected in the BBG100 sample. When tested for its biocontrol potential, wild-type strain ATCC 6633 was almost ineffective for reducing a Pythium infection of tomato seedlings. However, treatment of seeds with the BBG100 overproducing strain resulted in a marked increase in the germination rate of seeds. This protective effect afforded by mycosubtilin overproduction was also visualized by the significantly greater fresh weight of emerging seedlings treated with BBG100 compared to controls or seedlings inoculated with the wild-type strain. [less ▲]

Bacillus subtilis M4 decreases plant susceptibility towards fungal pathogens by increasing host resistance associated with differential gene expression

in Applied Microbiology & Biotechnology (2005), 67(5), 692-698

Results presented in this paper describe the ability of Bacillus subtilis strain M4 to reduce disease incidence caused by Colletotrichum lagenarium and Pythium aphanidermatum on cucumber and tomato ... [more ▼]

Results presented in this paper describe the ability of Bacillus subtilis strain M4 to reduce disease incidence caused by Colletotrichum lagenarium and Pythium aphanidermatum on cucumber and tomato, respectively. Disease protection in both pathosystems was most probably due to induction of resistance in the host plant since experiments were designed in order to avoid any direct contact between the biocontrol agent and the pathogen. Pre-inoculation with strain M4 thus sensitised both plants to react more efficiently to subsequent pathogen infection. In cucumber, the use of endospores provided a disease control level similar to that obtained with vegetative cells. In contrast, a mixture of lipopeptides from the surfactin, iturin and fengycin families showed no resistance-inducing potential. Interestingly, treatment with strain M4 was also associated with significant changes in gene transcription in the host plant as revealed by cDNA-AFLP analyses. Several AFLP fragments corresponded to genes not expressed in control plants and specifically induced by the Bacillus treatment. In support to the macroscopic protective effect, this differential accumulation of mRNA also illustrates the plant reaction following perception of strain M4, and constitutes one of the very first examples of defence-associated modifications at the transcriptional level elicited by a non-pathogenic bacterium in a host plant. [less ▲]

Physiological and physico-chemical factors modulating ISR elicitor production by Pseudomonas putida.

Conference (2005)

Resistance induced in cucumber and tomato by a non-pathogenic Pseudomonas putida strain

in Parasitica (2005), 61

Some plant growth promoting rhizobacteria are able to stimulate inducible defense mechanisms that render the host plant less susceptible to a subsequent pathogen attack. This phenomenon, called induced ... [more ▼]

Some plant growth promoting rhizobacteria are able to stimulate inducible defense mechanisms that render the host plant less susceptible to a subsequent pathogen attack. This phenomenon, called induced systemic resistance (ISR), can occur in several plant species against a wide range of bacterial, viral and fungal pathogens. Despite extensive work, many aspects of the molecular basis underlying this rhizobacteria-mediated ISR remain unclear. In this context, we have studied for several years the ISR-mediated protective effect of a particular strain, Pseudomonas putida BTP1. In this paper, we present the results obtained by using BTP1 for disease reduction against anthracnose caused by Colletotrichum lagenarium on cucumber and grey mold caused by Botrytis cinerea on tomato. As a result of cucumber treatment with BTP1, we observed an enhanced hydroperoxide lyase activity that could restrict pathogen ingress since this enzyme, acting downstream in the so-called oxylipin pathway, forms short chain aldehydes considered as “volatile phytoalexins”. By contrast, this phenomenon is not involved in the protective effect afforded by the strain in tomato. In this case, disease reduction is more seemingly associated with an early accumulation of antifungal compounds stimulated by the bacterium, showing that specific ISR-related metabolic pathways may be activated in different plants by the same microorganism. [less ▲]