Abstract
Soil bacteria can benefit from co-occurring soil fungi in respect of the acquisition of carbonaceous nutrients released by fungal hyphae and the access to novel territories in soil. Here, we investigated the capacity of the mycosphere-isolated bacterium Burkholderia terrae BS001 to comigrate through soil along with hyphae of the soil fungi Trichoderma asperellum, Rhizoctonia solani, Fusarium oxysporum, F. oxysporum pv lini, Coniochaeta ligniaria, Phanerochaete velutina, and Phallus impudicus. We used Lyophyllum sp. strain Karsten as the reference migration-inciting fungus. Bacterial migration through presterilized soil on the extending fungal hyphae was detected with six of the seven test fungi, with only Phallus impudicus not showing any bacterial transport. Much like with Lyophyllum sp. strain Karsten, intermediate (106–108 CFU g-1 dry soil) to high (>108 CFU g-1 dry soil) strain BS001 cell population sizes were found at the hyphal migration fronts of four fungi, i.e., T. asperellum, Rhizoctonia solani, F. oxysporum and F. oxysporum pv lini, whereas for two fungi, Coniochaeta ligniaria and Phanerochaete velutina, the migration responses were retarded and population sizes were lower (103–106 CFU g-1 dry soil). Consistent with previous data obtained with the reference fungus, migration with the migration-inciting fungi occurred only in the direction of the hyphal growth front. Remarkably, Burkholderia terrae BS001 provided protection from several antifungal agents to the canonical host Lyophyllum sp. strain Karsten. Specifically, this host was protected from Pseudomonas fluorescens strain CHA0 metabolites, as well as from the anti-fungal agent cycloheximide. Similar protection by strain BS001was observed for T. asperellum, and, to a lower extent, F. oxysporum and Rhizoctonia solani. The protective effect may be related to the consistent occurrence of biofilm-like cell layers or agglomerates at the surfaces of the protected fungi. The current study represents the first report of protection of soil fungi against antagonistic agents present in the soil provided by fungal-associated Burkholderia terrae cells.
Highlights
IntroductionBacteria and fungi live together in the same microhabitat (Johansson et al, 2004)
In many natural environments, bacteria and fungi live together in the same microhabitat (Johansson et al, 2004)
GROWTH AND MAINTENANCE OF MICROORGANISMS The fungal strains used in this study, i.e., the basidiomycetous Lyophyllum sp. strain Karsten (DSM2979), Rhizoctonia solani AG3, Trichoderma asperellum 302, Coniochaeta ligniaria ATCC44981, Phallus impudicus PI, Phanerochaete velutina PV, Fusarium oxysporum Fo47, and F. oxysporum pv. lini Foln3 were routinely grown on oat flake agar (OFA) plates, prepared with 30 g of oat flake and 15 g of agar (Duchefa, Haarlem, Netherlands) in demineralized water to 1 l, and sterilized at 121◦C for 21 min
Summary
Bacteria and fungi live together in the same microhabitat (Johansson et al, 2004). In such cohabitations, the two partners may have developed strategies to interact with each other, to the mutual success of the interaction (PartidaMartinez and Hertweck, 2005; Partida-Martinez et al, 2007a,b). The two partners may have developed strategies to interact with each other, to the mutual success of the interaction (PartidaMartinez and Hertweck, 2005; Partida-Martinez et al, 2007a,b) With basis in their mycelial way of growth, soil fungi are able to cross the air-filled gaps in natural soil (De Boer et al, 2005). Fungi proliferating in soil may serve as agents that enrich and transport particular bacterial species, e.g., pollutant-degrading soil bacteria (Furuno et al, 2010, 2012b; Wick et al, 2007, 2010)
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