Fungal hyphae promote bacterial contact-dependent killing during surface-associated growth

Bacterial contact-dependent killing in spatially structured systems is shaped by physical constraints and biological interactions. In this study, we demonstrate the importance of fungal hyphae in facilitating bacterial dispersal and promoting contact-dependent killing during surface-associated growth. Using Vibrio cholerae as the killing bacterium and Pseudomonas stutzeri as the target bacterium, we show that fungal hyphae act as dispersal agents that facilitate bacterial spatial intermixing and promote contact-dependent killing. Specifically, we show that dispersal along fungal hyphae increases the number of contacts between V. cholerae and P. stutzeri cells, which in turn increases the extent of killing via the type VI secretion system encoded by V. cholerae. This enables V. cholerae to achieve growth dominance despite initial population disadvantages. We further show that the effect of fungal hyphae on the killing efficacy of V. cholerae depends on flagellar motility. Our study underscores the multifaceted effects of fungal hyphae in enhancing bacterial dispersal and intensifying interspecies interactions, highlighting the ecological significance of fungal-bacterial interactions in spatially structured systems.