Fig. 5: Metabolomics and metagenomics analysis of microbial metabolism.

PCA score scatter based on a serum and b tumor metabolic profiling of non-stressed, stressed, and co-housed stressed tumor mice at the end of 40 days (n = 5 per group). Heatmap showing differential metabolic profiling in c serum and d tumor tissue among three groups (n = 5 per group). The concentration of acetate and stearoylcarnitine in the e serum and f tumor tissue of mice (n = 5 per group). The boxplot displays the distribution of concentrations for each metabolite, with the box representing the interquartile range (10th to 90th percentiles), the center line representing the median, and the whiskers representing the minimum and maximum values. g Concentration of acetate in the tumor tissue of tumor and stressed (CUS) tumor mice (n = 6 per group). h Contents of acetate in the feces of patients with MDD (n = 20) and HC (n = 20). i LEfSe analysis between tumor group and stressed tumor group in KEGG modules (n = 5 per group). j Overview of the Wood–Ljundahl pathway: K00198: anaerobic carbon-monoxide dehydrogenase catalytic subunit; K15022: formate dehydrogenase (NADP⁺) beta subunit; K01491: methylenetetrahydrofolate dehydrogenase (NADP⁺)/methenyltetrahydrofolate cyclohydrolase; K00297: methylenetetrahydrofolate reductase (NADH); K01438: acetyl-CoA synthase; K00625: phosphate acetyltransferase; K00925: acetate kinase. (k) The relative abundance of KOs associated with the Wood–Ljundahl pathway (n = 5 per group). Data were presented as mean ± SEM. Statistical significance was determined by one-way ANOVA followed by the Holm–Sidak test for (e, f) or two-sided Mann–Whitney U test for (k) and unpaired two-tailed Student’s t-test for (g, h). Significance levels are denoted as *p < 0.05; **p < 0.01; ***p < 0.001; “ns” indicates no significant difference. Source data and exact p values are provided in the Source data file.