Rhizosphere bacteria from sites with higher fungal densities exhibit greater levels of potential antifungal properties

A field study was performed to examine whether an increased density of saprotrophic fungi in the rhizosphere selects for bacteria with traits advantageous to living in a fungal-rich environment. Fast-growing bacteria were isolated from the rhizosphere of Carex arenaria (sand sedge) plants growing in fungal-poor (sand drifts) and fungal-rich (forest) sites in the Netherlands and screened for several potential antifungal properties, namely in vitro antagonism and the production of siderophores, cyanide and lytic enzymes. A higher incidence of putatively antifungal traits was generally found in bacteria isolated from fungal-rich soils, thus supporting the hypothesis that high fungal densities can impose a selection pressure on rhizosphere bacteria.