Enhanced Phytopathogen Biofilm Control in the Soybean Phyllosphere by the Phoresy of Bacteriophages Hitchhiking on Biocontrol Bacteria

Phage-based
biocontrol has shown notable advantages in
protecting
plants against pathogenic bacteria in agricultural settings compared
to chemical-based bactericides. However, the efficiency and scope
of phage biocontrol of pathogenic bacteria are limited by the intrinsic
properties of phages. Here, we investigated pathogen biofilm eradication
in the phyllosphere using the phoresy system of hitchhiking phages
onto carrier biocontrol bacteria. The phoresy system efficiently removed
the pathogen biofilm in the soybean phyllosphere, reducing the total
biomass by 58% and phytopathogens by 82% compared to the untreated
control. Biofilm eradication tests demonstrated a significant combined
beneficial effect (Bliss independence model, CI < 1) as phages
improved carrier bacteria colonization by 1.2-fold and carrier bacteria
facilitated phage infection by 1.4-fold. Transcriptomic analysis showed
that phoresy significantly enhanced motility (e.g., fliC and pilD genes) and energy metabolism (e.g., pgm and pgk genes) of carrier bacteria
and suppressed the defense system (e.g., MSH3 and FLS2 genes) and energy metabolism (e.g., petB and petC genes) of pathogens. Metabolomics analysis
revealed that the phoresy system stimulated the secretion of beneficial
metabolites (e.g., flavonoid and tropane alkaloid) that could enhance
stress response and phyllosphere protection in soybeans. Overall,
the phoresy of phages hitchhiking on biocontrol bacteria offers a
novel and effective strategy for phyllosphere microbiome manipulation
and bacterial disease control.