Fig. 8

Faecal microbiota composition in male and female mice exposed to Ref-Au or E175. Bacterial diversity based on the Shannon index in the faecal samples from male (A) and female (H) mice orally exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. Beta diversity based on Bray–Curtis distance in faecal samples from male (B) and female (I) mice orally exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. Relative abundance of Bacteroidetes, Firmicutes, Proteobacteria and Actinobacteria in faecal samples from male (C–F) and female (J–M) mice orally exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. Firmicutes/Bacteroidetes ratio in the faecal microbiota of male (G) and female (N) mice orally exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. Relative abundance of Bifidobacterium (O) and Akkermansia muciniphila (P) in females orally exposed to Ref-Au (10 µg/kg BW/d) or E175 (0.1, 1 and 10 µg/kg BW/d) for 13 weeks. For the Shannon index, differences were statistically tested using ANOVA, followed by Tukey’s test. For beta diversity, PERMANOVA, p < 0.05, followed by pairwise tests were performed. Asterisks indicate conditions that were significantly different from the controls (Ctrl). Changes in phylum relative abundances and the Firmicutes/Bacteroidetes ratio were statistically tested using ANOVA, p < 0.05, followed by Tukey’s test. The relative abundances of the genera Bifidobacterium and Akkermansia were statistically tested using the Kruskal–Wallis test, as the assumption of a normal distribution of data was not met, P < 0.05, followed by Dunn’s post hoc test