Bacterial volatile organic compounds attenuate pathogen virulence via evolutionary trade-offs

Area of Science:

• Microbiology
• Evolutionary Biology
• Plant Pathology

Background:

• Volatile organic compounds (VOCs) from soil bacteria possess antimicrobial properties and potential for biocontrol.
• The impact of VOCs on soil microbial ecology is known, but their influence on plant pathogen evolution remains understudied.

Purpose of the Study:

• To investigate the adaptation of Ralstonia solanacearum to VOCs produced by Bacillus amyloliquefaciens T-5.
• To determine how these adaptations affect the pathogen's virulence and identify underlying genetic mechanisms.

Main Methods:

• Experimental evolution of Ralstonia solanacearum exposed to a mixture of bacterial volatile organic compounds (VOCs).
• Phenotypic analysis of VOC-tolerance, antibiotic cross-tolerance, and pathogenicity in planta.
• Genetic analysis including whole-genome sequencing and reverse genetic engineering of key genes (wecA, pilM).

Main Results:

• VOC selection significantly increased VOC-tolerance and cross-tolerance to antibiotics in Ralstonia solanacearum.
• Increased VOC-tolerance resulted in a substantial reduction in R. solanacearum virulence, leading to near-complete loss of pathogenicity.
• Parallel mutations in wecA (lipopolysaccharide O-antigen) and pilM (type-4 pilus biosynthesis) were identified, correlating with enhanced tolerance and reduced virulence.

Conclusions:

• Microbial VOCs act as significant drivers of bacterial evolution, influencing pathogen adaptation and virulence.
• Bacterial volatile organic compounds (VOCs) can be leveraged in biocontrol strategies to select for less virulent pathogen strains through induced evolutionary trade-offs.
• Specific genetic mutations in wecA and pilM mediate the observed trade-offs between antimicrobial tolerance and virulence in Ralstonia solanacearum.