Pseudomonad strains for biocontrol of pythium infections in hydroponic greenhouses

Overview

This technology leverages naturally occurring Pseudomonas strains as a biological control agent to combat Pythium infections in hydroponic greenhouse operations. Pythium species are among the most damaging pathogens in hydroponic systems, causing root rot and significant crop losses. The solution exploits the bacteria's Type Six Secretion Systems (T6SS), molecular nanomachines that inject protein effectors directly into the cytoplasm of competing organisms, to achieve contact-dependent killing of Pythium hyphae.

The approach has been validated against 15 Pythium isolates sourced from hydroponic greenhouses in Ohio, California, Indiana, and New Jersey, demonstrating broad-spectrum potential across diverse geographic and operational conditions. This biocontrol strategy offers greenhouse operators a sustainable, targeted alternative to traditional chemical fungicides, reducing environmental impact while addressing the growing problem of fungicide resistance.

Technical specifications

Mechanism of action:

• Pseudomonas strains deploy T6SS to deliver protein effectors into Pythium hyphae cytoplasm
• Effectors contain conserved VgrG domains or are genetically linked to T6SS operons
• Killing is contact-dependent and species-specific

Validated performance:

• Complete hyphal killing observed after 24-hour incubation with bacteria at 400 CFU concentration on V8 agar
• Successful elimination of Pythium propagules from contaminated hydroponic water, confirmed by filtration and plating on selective antibiotic V8 plates
• Insertional mutagenesis of two T6SS-containing operons resulted in loss of virulence, confirming T6SS as the killing mechanism

Identification pipeline:

• In-frame gene truncation using synthesized sequences (~1800bp) inserted via pDONR1K18ms vector
• Electroporation and antibiotic selection for genomic integration
• Sucrose counter-selection for plasmid removal
• PCR confirmation of mutations and virulence assays to validate gene function
• Yeast two-hybrid (Y2H) screening to identify effector targets in Pythium

Technology readiness level

The technology is currently at TRL 4-5, having demonstrated proof-of-concept efficacy in laboratory and controlled hydroponic water conditions. Initial validation against multiple Pythium isolates has been completed, and the genetic basis of virulence has been confirmed through mutagenesis studies. Ongoing work focuses on identifying additional effector genes and understanding target interactions. Further development is needed to optimize formulation, scale production, and validate performance in commercial-scale greenhouse trials before market deployment.