Volatile organic compounds of the soil bacterium Bacillus halotolerans suppress pathogens and elicit defense-responsive genes in plants.

Volatile organic compounds (VOCs) produced by bacteria play an important, yet relatively unexplored role in interactions between plants and phytopathogens. In this study, the soil bacterium Bacillus halotolerans NYG5 was identified as a potent biocontrol agent against several phytopathogenic fungi (Macrophomina phaseolina, Rhizoctonia solani, Pythium aphanidermatum, and Sclerotinia sclerotiorum) through the production of VOCs. NYG5-emitted VOCs also inhibited the growth of bacterial pathogens (Agrobacterium tumefaciens, Xanthomonas campestris, Clavibacter michiganensis, and Pseudomonas syringae). When cultured in various growth media, NYG5 produced a variety of VOCs. Five distinct VOCs (2-methylbutanoic acid, 5-methyl-2-hexanone, 2,3-hexanedione, 2-ethyl-1-hexanol, and 6-methyl-2-heptanone) were identified using headspace GC-MS. 2,3-Hexanedione exhibited potent lethal effects on the tested phytopathogens and nematicidal activity against Meloidogyne javanica at a concentration of 50 ppm. In addition, 0.05 ppm 2,3-hexanedione stimulated the expression of pathogenesis-related genes 1 and 2 in Arabidopsis thaliana. Interestingly, 2,3-hexanedione is used as a food additive at higher concentrations than those tested in this study. Hence, 2,3-hexanedione is a promising biologically active compound that might serve as a sustainable alternative to common chemical pesticides and an elicitor of plant defense.

Bioinspired passive anti-biofouling surfaces preventing biofilm formation.

Biofilm formation enables bacteria to grow under unfavorable conditions, provides them with protection, and increases their resistance to antimicrobial agents. Once a biofilm has formed, it is difficult, and in some systems, impossible to treat. Strategies based on the release of biocidal agents have shown only transient efficiency. Herein, we present a novel bioinspired passive approach to the prevention of surface biofilm attachment by exploiting superhydrophobic surfaces formed via the self-assembly of paraffin or fluorinated wax crystals. Our surfaces show exceptional ability to inhibit biofilm formation of both Gram-positive Bacillus cereus and Gram-negative Pseudomonas aeruginosa over a 7 day period (up to 99.9% inhibition).