ACTIVITY 2. DEVELOPMENT OF A BIOCONTROL METHOD FOR OVERCOMING SALMONELLA PERSISTENCE ON FRESH PRODUCE IN THE FIELD
Activity Leader: Pascal Delaquis, AAFC-Summerland, Pascal.Delaquis@agr.gc.ca , T. (250) 494-6367
Develop a bacteriophage-based biopesticide for control of Salmonella on growing food plants (spinach, lettuce, tomatoes).
Bacteriophages for biocontrol must exhibit a broad host range to maximize target coverage, have low transducing frequency and be free of integration, virulence factor, toxin or antibiotic resistance genes. Their performance may be enhanced by the ability to produce enzymes capable of degrading polysaccharides implicated in attachment and the early stages of biofilm formation, a trait found in a range of bacteriophage that infect Gram-negative bacteria including Salmonella. Bacteriophage delivery for the control of bacterial plant diseases is typically achieved by direct foliar applications at critical stages during the production cycle and by incorporation into soil.
The following sub-objectives will be instrumental to reach the main goal:
Obj. 2.1 Isolation and characterization of bacteriophage that inhibit growth and/or attachment of Salmonella serovars
A collection of Salmonella bacteriophages isolated from disparate environments will be assembled and screened against a collection of well-characterized Salmonella isolates from Obj. 2.2 to determine host range.
Obj. 2.2 Determination of factors that contribute to the attachment and biofilm formation of Salmonella serovars
The most relevant food plant associated Salmonella serovars (concurrently sequenced in Activity 1) will be screened in order to determine relevant phenotypic groupings (e.g., curli, cellulose, biofilm production) related to adhesion and persistence on plant tissue surfaces.
Obj. 2.3 In vitro evaluation of Salmonella inhibition by bacteriophages
In vitro assays will be conducted to identify bacteriophages from Obj. 2.1 that inhibit Salmonella on plant tissues for the selection of isolates or mixtures thereof for in planta experimentation in Obj. 2.4.
Obj. 2.4 In planta evaluation of Salmonella inhibition by bacteriophages
Salmonella control using the bacteriophage preparations developed in Obj. 2.3 will be verified on mature lettuce plants, tomato plants and fruit. The suitability of different bacteriophage formulations and optimum timing of applications will be determined.
1) A collection of well characterized bacteriophages that inactivate the most common Canadian Salmonella serovars and the most common serovars found on food plants. Isolation of bacteriophages that specifically disrupt Salmonella biofilms.
2) Improved understanding of factors that contribute to the adhesion and persistence of Salmonella on food plants.
3) Identification of bacteriophages that inhibit Salmonella on food plants, and development of several bacteriophage cocktails for use in controlling Salmonella on food plants.
4) Means for the delivery of bacteriophages for the control of Salmonella on growing food plants.
5) Evaluation of the bacteriophage cocktails for control of Salmonella on growing food plants in a BSL III greenhouse trial.