Investigating Human Gut Microbiota-Host Interactions Using a Defined In Vitro Gut Microbiota Model in the Presence of FOS and Probiotics

Introduction Microorganisms inhabit body surfaces, particularly the gastrointestinal tract, forming the human gut microbiota (HGM). This microbiota performs essential functions through interactions among bacterial populations. Objective This work evaluates the interaction network in a reconstructed in vitro HGM during the fermentation of a β-glucan-enriched prebiotic Maitake extract. Methods The HGM in vitro model included a minimal core of Bacteroides cellulosilyticus, Clostridium symbiosum, Flavonifractor plautii, and Escherichia coli, along with probiotics (Lactobacillus and Bifidobacterium sp.). Growth experiments with Maitake and β-glucans were conducted in a batch bioreactor under anaerobic conditions, and bacterial strain modulation was monitored using RT-qPCR. Bacterial metabolites were extracted and analyzed via GC-MS. Findings In the HGM model, L. plantarum, B. lactis, and E. coli are the main strains that grow with Maitake extract. L. acidophilus is inhibited by B. lactis, which more efficiently utilizes the carbon source. Moreover, the probiotics inhibit the growth of C. symbiosum and F. plautii. In addition, B. cellulosilyticus competes with B. lactis and E. coli. E. coli does not grow in the presence of β-glucans, indicating it cannot use this molecule as a carbon source. L. plantarum and B. lactis are the dominant strains. B. lactis and B. cellulosilyticus still appear to have a competitive relationship. The results indicate that E. coli growth on Maitake extract isn't linked to β-glucans, which are primarily utilized by B. lactis and B. cellulosilyticus. Conclusion These results helped us understand the complex dynamics in the model, highlighting the competitive and cooperative interactions between the strains.