Lysobacter enzymogenes antagonizes soilborne bacteria using the type IV secretion system.

Area of Science:

• Microbiology
• Soil Science
• Bacterial Genetics

Background:

• Soil microbiomes are shaped by complex microbial interactions, including cell-cell killing.
• Type IV Secretion Systems (T4SS) are known virulence factors in pathogens and recently identified as inter-bacterial killing systems.
• Lysobacter enzymogenes is a soilborne bacterium with biocontrol potential.

Purpose of the Study:

• To investigate the role of T4SS in the killing behavior of the soilborne biocontrol bacterium Lysobacter enzymogenes OH11.
• To determine the impact of T4SS-mediated killing on soil microbiome composition and plant-pathogen interactions.

Main Methods:

• Genomic analysis of L. enzymogenes OH11 for T4SS components.
• Construction and analysis of T4SS knock-out mutants.
• Assays to evaluate inter-bacterial killing, antimicrobial activity, and plant protection.

Main Results:

• L. enzymogenes OH11 possesses genes encoding a functional T4SS.
• T4SS is essential for L. enzymogenes OH11's contact-dependent killing of other soil bacteria.
• T4SS activity reduced the efficacy of Pseudomonas spp. but protected carrots from Pectobacterium carotovorum.

Conclusions:

• T4SS is a key weapon for L. enzymogenes OH11 in inter-bacterial competition within the soil microbiome.
• T4SS-mediated killing influences the dynamics of the soil microbial community and plant health.
• This study reveals a novel function of T4SS in a beneficial soil bacterium.