A predator–prey interaction between myxobacteria and fungi mediated by outer membrane vesicles

Introduction

Outer membrane vesicles (OMVs) of Gram-negative bacteria mediate diverse functions in natural ecosystems. As a keystone taxon in soil, myxobacteria produce OMVs for cargo packing and microbial predation. However, the roles of OMVs in the interactions of myxobacteria with fungi remain poorly understood.

Objectives

This work aims to clarify the role of outer membrane vesicles in the interaction between myxobacteria and fungi and the regulatory mechanism during the interaction process.

Methods

We found that OMV plays a significant role in the interaction between Myxococcus sp. MP20 and Verticillium dahilae (Vd). We further identified the antifungal metabolites in OMV and verified the regulatory mechanism of OMV in the model strain Myxococcus xanthus DK 1622.

Results

We discover that Myxococcus sp. MP20 uses fungal networks and cotton root exudates for spatial dispersal. MP20 deploys the antifungal metabolites myxothiazole via OMVs to inhibit Vd growth by fusing the OMVs with fungal cells, thus restraining fungal invasion. Containment of myxothiazol within OMVs maintains an effective antifungal concentration on target cells. Furthermore, we demonstrate that the release of OMVs from MP20 was suppressed by iron via a newly discovered ABC transport system. In turn the lower number of OMVs reduced the antifungal behavior of MP20, suggesting that iron acquisition regulates OMVs-mediated competition between myxobacteria and fungi. Our findings thus unravel a novel antifungal tactic employed by myxobacteria to suppress fungi prey and control Verticillium wilt, which also provides new insights for understanding predator–prey interactions.