Antimicrobial mechanism of Limosilactobacillus fermentum SHY10 metabolites against pickle film-producing strain by metabolomic and transcriptomic analysis

The antimicrobial mechanism of Limosilactobacillus fermentum SHY10 metabolites on the pickle film-producing strain Candida parapsilosis B7 was investigated in this study. The results showed that SHY10 metabolites mainly consisted of peptides, alkaloids, nucleic acids, hormones and transmitters, and sterol lipids. Peptides and alkaloids accounted respectively for 15.5% and 22.7% of the total. The SHY10 metabolites induced pits on the cell membrane and death of film-producing strain, which were evidenced by scanning electron microscope and fluorescence. Metabolomic results showed that SHY10 metabolites had the most significant effect on the purine metabolic pathway of Candida parapsilosis B7. Transcriptome results showed that 505 genes of Candida parapsilosis B7 related to peroxisome, alpha-linolenic acid metabolism, ubiquinone and other terpenoid quinone biosynthesis were remarkably changed with the presence of SHY10 metabolites. The expression of PEX 3, PEX 12, ACOX 1 and wrbA determined by qRT-PCR were consistent with the transcriptome results. In summary, the SHY10 metabolites changed the expression of PEX 3, PEX 12, ACOX 1 and wrbA and affected peroxisome, alpha-linolenic acid metabolism, ubiquinone and other terpenoid quinone biosynthesis pathways, and eventually led to the death of Candida parapsilosis B7.