Journal: Cell Genomics

Article Title: Systematically investigating and identifying bacteriocins in the human gut microbiome

doi: 10.1016/j.xgen.2025.100983

Figure Lengend Snippet: In vitro assay of previously uncharacterized bacteriocins from diverse bacterial phyla (A) Antibacterial activity of 21 synthetic hypothetical bacteriocins (HBs) against both Gram-positive (+) and Gram-negative (−) bacteria. A red cross signifies that HBs cannot be identified by the prediction tool, while a green tick indicates successful detection. The activity screening was conducted at a concentration of 100 μg/mL, with activity being categorized into four groups (no activity, <25% inhibitory ratio or p > 0.05; low activity, 25% ≤ inhibitory ratio <50% and p < 0.05; medium activity, 50% ≤ inhibitory ratio <75% and p < 0.05; high activity, inhibitory ratio >75% and p < 0.05). HBs with high activity are highlighted in red. Asterisks in the activity-screening heatmap denote an inhibitory ratio of ≥90%, which is subject to further MIC examination (rightmost panel). Exact MIC values are indicated in the heatmap, with antibiotic vancomycin serving as the positive control. All assays were performed in three independent replicates. The MICs of vancomycin are 0.13 μg/mL (0.09 μM), 0.25 μg/mL (0.17 μM), 0.5 μg/mL (0.34 μM), and 2 μg/mL (1.38 μM). The MIC of HB2 is 25 μg/mL (6.17 μM). The MIC of HB5 is 25 μg/mL (5.10 μM). The MICs of HB7 are 0.78 μg/mL (0.31 μM), 12.5 μg/mL (5.01 μM), 25 μg/mL (10.01 μM), and 50 μg/mL (20.03 μM). The MIC of HB11 is 100 μg/mL (31.16 μM). The MIC of HB12 is 100 μg/mL (23.54 μM). (B) Membrane permeability assessed by PI uptake assay. Four bacteriocins (HB5, HB7, HB11, and HB12) were tested for their sensitive strain Bacillus timonensis DSM 25372, while HB2 was examined for Enterococcus ureasiticus DSM 23328. Vancomycin and nisin A were included as a negative and a positive control, respectively. Vehicle (DMSO) was the blank control. Statistical significance was computed by Dunnett’s test. All assays were performed in three independent replicates ( n = 3). Data are mean ± standard deviation. (C) Membrane potential of E. ureasiticus DSM 23328 treated with HB2. Vancomycin and 0.1% Triton X-100 were used as a negative and a positive control, respectively. Vehicle (DMSO) was the blank control. Statistical significance was given by Dunnett's test. All assays were performed in three independent replicates ( n = 3). Data are mean ± standard deviation. (D) The synergistic interaction between bacteriocins and vancomycin (Van) was assessed by checkerboard assays with 2-fold serial dilutions starting at 2 × MIC to 0.125 × MIC. The lollipop plot shows the fractional inhibitory concentration index (FICI) values.

Article Snippet: Enterococcus ureasiticus , Leibniz Institute DSMZ , DSM 23328.

Techniques: In Vitro, Activity Assay, Bacteria, Concentration Assay, Positive Control, Membrane, Permeability, Control, Standard Deviation