Fig. 3

Impact of dietary fat content in the murine regulatory response to L. monocytogenes infection (D16 in relation to D13). a The number of goblet cells (D16) present on one villus was quantified and divided by the villus length (groups were blinded). Statistical analysis was conducted using one-way ANOVA and Dunnett’s multiple comparison test in relation to D0. Representative histological images demonstrating goblet cell density (left representative of LF group and right representative of HF group on day D16). Ileal paraffin sections of 5 μm were stained with alcian blue and periodic acid-Schiff (PAS) and counterstained with Schiff reagent and Nuclear Fast Red solution. Arrows indicate examples of goblet cells. b Effects of diet on host gene expression post-infection using qRT-PCR. Gene expression relative to D13 (pre-infection), within the same dietary group, in both ileum and liver on day 16 of dietary feeding (3 days post-infection). Represented as log₂ of the fold change between the condition and the control (same diet D13). Statistical analysis was conducted using one-way ANOVA and Dunnett’s multiple comparison test. c Comparison of the changes in bacterial communities during controlled feeding. Unweighted Unifrac PCoA faecal microbiota distances between groups of mice fed different diets (blue representing LF; red representing HF) over indicated time points (D13, D15, D16). p values were measured using an Adonis test (p value = 0.00099, R² is 0.148). d Changes in bacterial percentage of abundance during dietary shifts (D13 to D16) of the most abundant phyla, Bacteroidetes and Firmicutes. e Changes in bacterial abundance between LF and HF diets at the family level for the most abundant phyla. A volcano plot showing the fold change between high- and low-fat diets at D16. Each point represents an operational taxonomic unit (OTU). The x-axis represents in the log₂ of the fold change whilst the y-axis is the negative log₁₀ of DESeq2 p values adjusted for multiple testing using the false discovery rate method. Points to the right of the plot with positive log2FoldChange values represent bacterial taxa with increased abundance in the mice on the HF diet relative to the mice on the LF diet and those with negative log2FoldChange values represent bacterial taxa with increased abundance in the LF diet relative to the HF diet. The horizontal black line represents the cutoff for statistical significance, an adjusted p value of 0.05. f A correlation between the host regulatory response and the microbiota at the genus level on day 16. Spearman correlation, between the diet-dependent relative abundance of bacterial genera (arrows represent abundance in the mice on the HF diet relative to the mice on the LF diet) and the fold change for genes in both ileum and liver. Results shown separately for host immunity, tight junctions and host-pathogen interaction genes. Represented are only significant hits, p < 0.05. Error bars represent SEM