Fungal hyphae colonization byBacillus subtilisrelies on biofilm matrix components

Abstract

Bacteria interact with their environment including microbes and higher eukaryotes. The ability of bacteria and fungi to affect each other are defined by various chemical, physical and biological factors. During physical association, bacterial cells can directly attach and settle on the hyphae of various fungal species. Such colonization of mycelia was proposed to be dependent on biofilm formation by the bacteria, but the essentiality of the biofilm matrix was not represented before.Here, we demonstrate that secreted biofilm matrix components of the soil-dwelling bacterium, Bacillus subtilis are essential for the establishment of a dense bacterial population on the hyphae of the filamentous black mold fungus, Aspergillus niger and the basidiomycete mushroom, Agaricus bisporus. We further illustrate that these matrix components can be shared among various mutants highlighting the community shaping impact of biofilm formers on bacteria-fungi interactions.

Impact of fungal hyphae on growth and dispersal of obligate anaerobic bacteria in aerated habitats

“…Unlike in tightly packed industrial biofilms, soil fungi often develop extensively fractal mycelia that allow them to access heterogeneously distributed nutrients and carbon sources (22) and to bridge mycelial source-and sink-regions (23). Forming hyphae with lengths of ≈10 2 m g -1 in arable and up to 10 4 m g -1 in forest topsoil (19), mycelia thereby also serve as important pathways for bacterial dispersal ('fungal highways') (24) enabling the colonization of new habitats (25)(26)(27)(28), horizontal gene transfer (29), or predation (30). Expressing hydrophobic cell-wall proteins (hydrophobins), hyphae thereby overcome air-water interfaces and bridge air-filled pores with nutrient-rich aqueous zones containing little or no oxygen.…”

Fungal–bacterial interaction selects for quorum sensing mutants with increased production of natural antifungal compounds

“…Antagonistic and mutualistic behaviors, mediated by the exchange of small diffusible secondary metabolites, facilitate microbial adaptation to the complex communal lifestyles. Among them, fungi and bacteria are found living together in a wide variety of soil environments frequently involved in complex interactions shaped by several molecular determinants, such as motility, quorum sensing (QS), bacterial secretion system, and secondary metabolites 2,3 .…”

“…2c). Post-ST showed notable reduction in intensity of surfactin ions and of peaks with masses indicative of plipastatin, identified through spectrum library matching and feature-based molecular networking 3,21,22 . Importantly, post-ST clustered together with a B. subtilis NCBI 3610 surfactin-defective mutant 23 , confirming the role of surfactin in separation between the groups (Fig.…”