Abstract
Soil microorganisms coexist and interact showing antagonistic or mutualistic behaviors. Here, we show that an environmental strain of Bacillus subtilis undergoes heritable phenotypic variation upon interaction with the soil fungal pathogen Setophoma terrestris (ST). Metabolomics analysis revealed differential profiles in B. subtilis before (pre-ST) and after (post-ST) interacting with the fungus, which paradoxically involved the absence of lipopeptides surfactin and plipastatin and yet acquisition of antifungal activity in post-ST variants. The profile of volatile compounds showed that 2-heptanone and 2-octanone were the most discriminating metabolites present at higher concentrations in post-ST during the interaction process. Both ketones showed strong antifungal activity, which was lost with the addition of exogenous surfactin. Whole-genome analyses indicate that mutations in ComQPXA quorum-sensing system, constituted the genetic bases of post-ST conversion, which rewired B. subtilis metabolism towards the depletion of surfactins and the production of antifungal compounds during its antagonistic interaction with S. terrestris.
Highlights
Soil microorganisms coexist and interact showing antagonistic or mutualistic behaviors
We have previously observed that B. subtilis isolated from the rhizosphere of onion plants inhibits the growth of the soil fungal pathogen S. terrestris[17]
Concluding remarks Here, we describe the strategies employed in the warfare undertaken by a soil strain of B. subtilis during the antagonistic interaction with the plant fungal pathogen S. terrestris
Summary
Soil microorganisms coexist and interact showing antagonistic or mutualistic behaviors. The ability of B. subtilis to sense small molecules produced by a wide range of soil microorganisms indicates the presence of broad response mechanisms to neighboring species In this sense, B. subtilis became an interesting model to develop strategies for the biological control of a wide range of organisms, such as bacteria[6], fungi[7,8], nematodes[9], or even insects[10,11]. B. subtilis became an interesting model to develop strategies for the biological control of a wide range of organisms, such as bacteria[6], fungi[7,8], nematodes[9], or even insects[10,11] This capacity stems from the numerous metabolites secreted by B. subtilis, of which many play dual roles as antimicrobial compounds and signaling molecules, participating in processes, such as regulation of development, biofilm formation, and inhibition of virulence factors released by competitors[12,13,14]. Bacterial QS systems are not restricted to communication within their own species but are capable of receiving signals from and/or sending them to unrelated species, which might end up into behavioral modifications of one or more interacting partners[16]
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