Kosakonia cowanii Ch1 Isolated from Mexican Chili Powder Reveals Growth Inhibition of Phytopathogenic Fungi

Abstract

<i>Kosakonia cowanii</i> strain Ch1 was isolated from Mexican chili powder, and the genome was sequenced. The genome was 4,765,544 bp in length, with an average G + C content of 56.22%, and a plasmid (pCh1) of 128,063 bp with an average G + C content of 52.50%. A phylogenetic analysis revealed a close relation with pathogenic strains; nevertheless, some virulence-related genes were absent, and this genetic characteristic may explain the fact that <i>K. cowanii</i> Ch1 behaved as a non-pathogenic strain when infection assays were performed on the leaves and fruits of <i>Capsicum annuum</i> L. Surprisingly, we observed that this bacterial strain had the ability to spread throughout serrano pepper seeds. Furthermore, <i>K. cowanii</i> Ch1 was evaluated for the production of volatile organic compounds (VOCs) against fungal pathogens, and the results showed that <i>Alternaria alternata</i> and <i>Sclerotium rolfsii</i> were inhibited in a radial mycelial growth assay by a mean rate of 70% and 64%, while <i>Fusarium oxysporum</i> was inhibited by only approximately 10%. Based on the headspace solid-phase microextraction combined with the gas chromatography mass spectrometry (HS-SPME-GC-MS), 67 potential VOCs were identified during the fermentation of <i>K. cowanii</i> Ch1 in TSA medium. From these VOCs, nine main compounds were identified based on relative peak area: dodecanoic acid; 3-hydroxy ethanol; 1-butanol-3-methyl; acetaldehyde; butanoic acid, butyl ester; cyclodecane; 2-butanone, 3-hydroxy; disulfide, dimethyl and pyrazine-2,5-dimethyl. Our findings show the potential of <i>K. cowanii</i> Ch1 for the biocontrol of fungal pathogens through VOCs production and reveal additional abilities and metabolic features as beneficial bacterial specie.