Modulating Surfactin Biosynthesis in Bacillus subtilis R31 Enhances Behavioural Traits and Biocontrol Efficacy...

Surfactin, a lipopeptide antibiotic and quorum-sensing (QS) mediator from Bacillus subtilis, has dual functions in microbial ecology and plant disease suppression. This study engineered B. subtilis R31 to overproduce comK and phrC, key regulators of surfactin biosynthesis, increasing surfactin yield by 45% compared to the WT strain. While elevated surfactin enhanced antimicrobial potential, comK-mediated overproduction impaired biofilm formation and swarming motility, but rhizosphere colonisation was mostly unaffected. 16S rRNA sequencing of banana rhizospheres showed that surfactin selectively shaped the microbial community by enriching beneficial Bacillus species. Mechanistic studies confirmed surfactin's dual role as an antimicrobial and an intercellular signalling molecule for coordinated development in Bacillus populations. These results reveal the molecular mechanisms of R31-mediated suppression of banana Fusarium wilt and offer a strategy for engineering synthetic microbial consortia by manipulating metabolic signalling pathways.