Weaponizing volatiles to inhibit competitor biofilms from a distance

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.

Evaluation of biological activities of two essential oils as a safe environmental bioinsecticides: case of Eucalyptus globulus and Rosmarinus officinalis

All works of this article were conducted to investigate chemical composition and insecticidal and antimicrobial properties of Eucalyptus globulus and Rosmarinus officinalis essential oils isolated by hydro-distillation of its aerial parts. Analysis of the essential oils on the basis of gas chromatography and mass spectrometry (GC/FID and GC/MS) revealed the presence of 82 organic volatiles representing 98.63% of the total constituents of Eucalyptus globulus and the presence of 45 organic volatiles representing 98.53% of the total constituents of Rosmarinus officinalis. The major compounds for Eucalyptus globulus were estragole (28.14%), terpinolene (7.12%), 1,4-hexadiene-5-methyl-3-(1-methylethylidene) (7.01%), linalool (5.54%) and furfural (4.66%) and for Rosmarinus officinalis were (-)-camphor (31.16%) and β-caryophyllene (18.55%), 3,4-dimethyl-(Z,Z)-2,4-Hexadiene (9.08%), α-fenchene (4.67%), cis-verbenone (4.33%) and Bornyl acetate (3.4%). The efficacy of the two essential oils was evaluated on the insect pests Sitophilus granarius of wheat and was remarkable with lethal doses of 50% tending towards 1 μL·cm–3. The broth microdilution method as a complementary test was conducted to test the antimicrobial activity of the essential oil against: Staphylococcus aureus, Enterococcus faecium, Listeria monocytogenes, Bacillus subtilis, Escherichia coli, Yersinia enterocolitica, Pseudomonas aeruginosa and Candida albicans, further for the two oils of shows promising activity against all strains.

A Barcoded Polymer-Based Cross-Reactive Spectroscopic Sensor Array for Organic Volatiles

The development of cross-reactive sensor arrays for volatile organics (electronic noses, e-noses) is an active area of research. In this manuscript, we present a new format for barcoded polymer sensor arrays based on porous polymer beads. An array of nine self-encoded polymers was analyzed by Raman spectroscopy before and after exposure to a series of volatile organic compounds, and the changes in the vibrational fingerprints of their polymers was recorded before and after exposure. Our results show that the spectroscopic changes experienced by the porous spectroscopically encoded beads after exposure to an analyte can be used to identify and classify the target analytes. To expedite this analysis, analyte-specific changes induced in the sensor arrays were transformed into a response pattern using multivariate data analysis. These studies established the barcoded bead array format as a potentially effective sensing element in e-nose devices. Devices such as these have the potential to advance personalized medicine, providing a platform for non-invasive, real-time volatile metabolite detection.