Dellaglioa Algida Cell-Free Supernatant Inhibits Pseudomonas Fluorescence and Pseudomonas Fragi by Destroying Cell Membranes

The aim of this study was to examine the components of the cell-free supernatant (CFS) derived from a novel strain of psychrophilic <i>Lactobacillus</i>, <i>Dellaglioa algida</i>, and to further elucidate the impact of this CFS on various cellular processes. Specifically, we sought to understand its effects on the cell membrane, protein and DNA release, protease activity, and metabolites of <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i>, thereby clarifying the antibacterial mechanism involved. The CFS components were analyzed using Gas Chromatography-Mass Spectrometry (GC-MS), the Coomassie Brilliant Blue method, and the phenol-sulfuric acid method. The inhibitory effect of the CFS on <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i> was assessed using the ethidium bromide (EB) assay, Oxford cup assay, and ultramicroassay. Additionally, we analyzed the metabolites produced by <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i> when treated with the CFS. The findings reveal that the CFS of <i>Dellaglioa algida</i> contains 94 volatile components, with protein and sugar concentrations of 32.857 ± 0.9705 mg/mL and 98.250 ± 4.210 mg/L, respectively. The CFS induces varying degrees of damage to the cell membranes of both <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i>, leading to the release of intracellular proteins and DNA. Furthermore, the CFS reduced the protease activity and metabolic capacity of <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i>. These results enhance our understanding of the mechanism by which psychrophilic <i>Dellaglioa algida</i> inhibits <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i>, confirming that its inhibitory effect predominantly occurs through damage to the biological cell membranes of <i>Pseudomonas</i>. <i>Dellaglioa algida</i> is a newly identified cold-adapted inhibitor of <i>Pseudomonas</i>, indicating that its CFS is an effective microbial inhibitor in cold environments. This discovery suggests potential applications in inhibiting the growth and reproduction of <i>Pseudomonas fluorescens</i> and <i>Pseudomonas fragi</i> in food, pharmaceuticals, perfumes, and other chemicals, providing a valuable new reference for industrial preservation.