Weaponizing volatiles to inhibit competitor biofilms from a distance

Abstract

The soil bacterium Bacillus subtilis forms beneficial biofilms that induce plant defences and prevent the growth of pathogens. It is naturally found in the rhizosphere, where microorganisms coexist in an extremely competitive environment, and thus have evolved a diverse arsenal of defence mechanisms. In this work, we found that volatile compounds produced by B. subtilis biofilms inhibited the development of competing biofilm colonies, by reducing extracellular matrix gene expression, both within and across species. This effect was dose-dependent, with the structural defects becoming more pronounced as the number of volatile-producing colonies increased. This inhibition was mostly mediated by organic volatiles, and we identified the active molecules as 3-methyl-1-butanol and 1-butanol. Similar results were obtained with biofilms formed by phylogenetically distinct bacterium sharing the same niche, Escherichia coli, which produced the biofilm-inhibiting 3-methyl-1-butanol and 2-nonanon. The ability of established biofilms to inhibit the development and spreading of new biofilms from afar might be a general mechanism utilized by bacterial biofilms to protect an occupied niche from the invasion of competing bacteria.

Resolving the conflict between antibiotic production and rapid growth by recognition of peptidoglycan of susceptible competitors

“…For the generation of the Luminescence reporter P srfAA - lux we performed restriction free cloning 5 using the plasmid pBS3C-lux 6 , which contains a functional luciferase operon (luxABCDE) . Briefly, promoter region was amplified from B. subtilis chromosomal DNA, using primers listed in supplementary Table S2 and ligated into plasmid.…”

“…Bacillus subtilis clade contains several species of Gram-positive, soil dwelling, beneficial bacteria, that employ multiple strategies to compete with neighbour communities 2,6–12 .One major class of antibiotics produced by bacteria are the Non-Ribosomal Peptides (NRP), which are synthesized by large multi-enzyme complexes of NRP synthases (NRPs) 2,13,14 . B. subtilis encodes four different NRP biosynthetic clusters, which are responsible for the biosynthesis of surfactin, bacillaene, bacilysin and plipastatin 2,15–18 .…”

Multi-Strain and -Species Investigation of Volatile Metabolites Emitted from Planktonic and Biofilm Candida Cultures

“…Other previously reported bioactive components that were detected in the Candida volatilomes included ethanol [ 37 , 39 , 40 ]; phenylethyl alcohol [ 41 , 42 ]; 1-butanol, 3-methyl- (isoamyl alcohol) [ 37 , 39 , 40 , 41 , 42 ]; 1-butanol, 3-methyl-, acetate- (isoamyl acetate) [ 37 , 39 , 40 ]; ethyl acetate [ 37 , 39 , 40 ]; and propanoic acid, 2-methyl, ethyl ester [ 37 , 41 ]. However, although these compounds are highly common across the microbial kingdoms, it is suspected that only species-specific combinations and abundances of them elicit antimicrobial effects [ 43 ]. These effects are determined using volatilomic bioactivity assays, a field of study that is still in the early stages of development.…”

An open-source computational tool for measuring bacterial biofilm morphology and growth kinetics upon one-sided exposure to an antimicrobial source

“…Traditional methods of assessing biofilm robustness often utilize measures that relate to colony response to various types of non-optimal environmental conditions. These include conditions such as mechanical stress 21 , nutrient stress 14 , 22 , application of various anti-biofilm agents 23 and presence of competing species 24 .…”