The antifungal and other bioactive properties of the volatilome ofStreptomyces scabiei

Volatile compounds (VCs) produced by most host-associated bacteria remain largely unexplored despite their potential roles in suppressing microbial competitors and facilitating host colonization. This study investigated the volatilome ofStreptomyces scabiei87-22, the model species for causative agents of common scab in root and tuber crops, under culture conditions that completely inhibited fungal growth, including the phytopathogensAlternaria solaniandGibberella zeae. Bicameral assays confirmed that these inhibitory effects were at least partially mediated by VCs. Using GC × GC TOFMS, 36 VCs were unambiguously identified as products ofS.scabiei87-22 metabolic activity. These included mainly ketones and aromatic compounds (both benzene derivatives and heterocycles), along with smaller contributions from other chemical families including sulfur-containing compounds, nitriles, esters, terpenoids, an amide, and an aldehyde. A literature survey suggests that many of these VCs possess antibacterial, antifungal, anti-oomycete, nematocidal, and insecticidal effects, while the bioactivity of others remains speculative, having been identified only within complex volatile mixtures. Among those with known antifungal properties, dimethyl trisulfide, 2-heptanone, and creosol inhibited the growth of the fungal pathogens tested in this study. In addition, we reveal here that 3-penten-2-one is also a strong inhibitor of fungal growth. Remarkably, despiteS.scabiei87-22 being defined as a pathogen, some of its VCs were associated with plant growth promotion and defense stimulation. Overall, our work highlights the remarkable potential ofS.scabiei87-22 to produce VCs with diverse bioactivities including fungal pathogen inhibition and priming plant resistance.