## 4 Discussion  
### Microbiota Interindividual Diversity among Donors Was Pooled in the Fecal Inoculum  
In the short-term simulation of the luminal microbiota conducted in this work, the fecal material was donated by three female healthy adults. The amplification of fecal DNA  
Figure 5: AhR transcriptional activity induced by the metabolic output samples and the agonist control TCDD. The three AhR-reporter gene cell lines (HepG2, T47D, HT29) were exposed in triplicate to the samples from the three independent repetitions of the colon simulation (n = 9). Results are expressed as mean fold induction \(\pm\) SD of luminescence prompted by the exposed cells when compared with untreated cells in the same assay plate. (**a**) Exposure dose 1:20 \(\upmu\)L of sample + 30 \(\upmu\)L of fermentation medium, (**b**) exposure dose 2:50 \(\upmu\)L of sample. Treatments corresponded to filtered, sterilized supernatant harvest from the colonic fermentation at the inoculation day (0 h) and after 24 h, 48 h, and 72 h. Differences between treatment in each cell line were compared, and statistical significance is indicated as \(p\) < 0.05 (*), \(p\) < 0.01 (**), and \(p\) < 0.001 (***). Lowercase letters represent differences in AhR induction as compared with the EC\({}_{50}\) of TCDD in the respective cell line, a: significantly greater than TCDD \(p\) < 0.001, and b: effects significantly lower than TCDD \(p\) < 0.001.  
targeting the 165 rRNA gene allowed us to estimate the abundance of bacterial populations in the fecal inoculum. The microbial composition in the stools (see Figure 1) was characterized by an over-representation of Firmicutes phylum, which categorizes the donors as enterotype 3 (the most common one) [48]. However, enterotype 3 is commonly driven by a high abundance of the _Ruminococcus_ genus [49], which was not really the case. A significant presence of _Coproococcus_ characterized fecal samples from donor 1, which did not resemble donors 2 and 3. Meanwhile, the highly heritable _Christensenellaceae_[50], mainly represented by the genus _Christensenellaceae_R-7_group_, was found in high abundance in all donors (>6%), particularly donor 1, who also exhibited the highest abundance of _Bacteroides_ (-9%). The UCG-002 genus from _Oscillospirace_ family was found abundantly in all stool samples, but especially in donor 2 (12.5%). Similarly, _Oscillospirates_ge_ was abundant mainly in feces from donor 2 (-9%), but also in donor 3 (6.3%). The family _Oscillospiraceae_ has been negatively correlated with cholesterol levels in Mexican children suffering from obesity [51]. Furthermore, the presence of the _Oscillospirace_ family in the stool is associated with lower extra-intestinal pain in women suffering from irritable bowel syndrome (IBS) [52]. A recent detailed analysis (in >6000 subjects) of _Oscillospira_ has revealed this genus as a possible aggravating biomarker of constipation, suggesting a genera-specific role within this family in the human gut microbiota yet to be analyzed [53]. The relatively new sub-branch _Alistipes_ genus from the Bacteroidetes phylum was identified in high abundance (-9%) only in donor 2. Dysbiosis of this population in humans appears to play either a beneficial or detrimental role. This is particularly important in the context of colorectal cancer and intestinal inflammatory conditions [54]. The genus _Phascalorctobacterium_ was also exclusively identified in donor 2. Previous studies have demonstrated a high colonization rate of the _Phascalorctobacterium facicum_ species in human feces [55]. However, only a few works are available on this genus, despite its potential correlation with the mood and metabolic state of humans [56]. The _Faecalibacterium_ genus is an important population in human feces, and, within it, _Faecalibacterium_ _prusuntizii_ is one of the most abundant species in the human gut. This commensal bacterium is a butyrate producer and has a pleiotropic but mostly beneficial role in the gastrointestinal tract [57].