It Takes Two to Tango: A Bacterial Biofilm Provides Protection against a Fungus-Feeding Bacterial Predator

Abstract

Fungus-bacterium interactions are widespread, encompass multiple interaction types from mutualism to parasitism, and have been frequent targets for microbial inoculant development. In this study, using in vitro systems combined with confocal laser scanning microscopy and real-time quantitative PCR, we test whether the nitrogen-fixing bacterium Kosakonia radicincitans can provide protection to the plant-beneficial fungus Serendipita indica, which inhabits the rhizosphere and colonizes plants as an endophyte, from the fungus-feeding bacterium Collimonas fungivorans. We show that K. radicincitans can protect fungal hyphae from bacterial feeding on solid agar medium, with probable mechanisms being quick hyphal colonization and biofilm formation. We furthermore find evidence for different feeding modes of K. radicincitans and C. fungivorans, namely “metabolite” and “hyphal feeding”, respectively. Overall, we demonstrate, to our knowledge, the first evidence for a bacterial, biofilm-based protection of fungal hyphae against attack by a fungus-feeding, bacterial predator on solid agar medium. Besides highlighting the importance of tripartite microbial interactions, we discuss implications of our results for the development and application of microbial consortium-based bioprotectants and biostimulants.

Quorum Sensing-Dependent Invasion of Ralstonia solanacearum into Fusarium oxysporum Chlamydospores

“…Biofilm formation by bacteria on fungal mycelia has been sporadically reported ( 58 – 60 ). However, we were the first to discover that biofilms are essential for bacterial endoparasitism within fungi.…”

Quorum sensing-dependent invasion ofRalstonia solanacearumintoFusarium oxysporumchlamydospores

“…Biofilm formation by bacteria on fungal mycelia has been occasionally reported (58)(59)(60). However, it was discovered that biofilm are essential for bacterial endoparasitism within fungi.…”