My research has focused mainly on the potential application of probiotics and their metabolites to modulate the gut microbiota positively and for food safety. We have conducted multiple studies to investigate the probiotic potential of commensal bacteria, their metabolite production, and stability during transit in the gut, and interaction with gut microbiota in- and ex- vivo. My research centers on gut microbiome physiology, its mechanistic modulation by nutritional and xenobiotic factors, and interplay with the host, and is built with around three themes: I) Gut Neuromicrobiology, 2) Interplay Xenobiotics-Microbiota-Nutrition, and 3) Investigation of new probiotic-prebiotic-postbiotic-symbiotic formulations with positive modulation of the gut microbiota and the host.
I. Neuromicrobiology: how probiotics influence the gut-brain axis?
Our gut is populated by a complex microbial community, known as the gut microbiota, which has been linked to many health disorders, including mental health. Psychobiotics are beneficial bacteria (probiotics) or support for such bacteria (prebiotics) that can positively modulate microbiota–gut–brain interactions. While some studies reported mitigated efficacy, several trials support a role for psychobiotics in the normalization of brain processes related to stress responses and mood improvements. The mechanisms by which psychobiotics modulate the microbiota–gut–brain axis and improve mental health remain uncertain but are likely microbial strain-specific. Gut bacteria produce a range of neurotransmitters, including g-aminobutyric acid (GABA), acetylcholine, dopamine, and serotonin, which, beyond interacting with intestinal physiology, can transit through neural pathways linking the enteric and central nervous systems and influence brain functioning. However, there is limited understanding of the neurochemical mechanisms by which psychobiotics orchestrate the microbiota-gut-brain axis, a prerequisite for developing evidence-based microbiota-targeted interventions. Findings from this research will inform the design and development of next-generation probiotics or functional food products with psychobiotic properties, which will be important for the community at large as they will hold the potential to improve human mental health.
- Mousavi R.A., Mottawea W., Hassan H., Audet M.C., and Hammami. R*.(2022) Screening, characterization, and growth of γ-aminobutyric acid-producing probiotic candidates from food origin under simulated colonic conditions. Journal of Applied Microbiology https://doi.org/10.1111/jam.15550.
II. Xenobiotics in the gut – protecting human gut microbiota from psychotropics using probiotics
There is an increasing interest in how therapeutic drugs (xenobiotics) could affect and alter the human gut microbiota composition and function. While some knowledge is accumulating on the detrimental impact of some psychotropics on isolated strains or the gut microbiota of animal models, information about other classes of psychotropics and representative species from the human gut is poorly investigated. The antimicrobial effect of psychotropic drugs is usually neglected as a confounding factor when investigating gut microbiome biomarkers, knowing that patients are generally put in long-term medication. There is an urgent need to clarify the real contribution of the antimicrobial role of psychotropics and the subsequent consequences to gut microbiota structure and metabolism. Our findings provide evidence that psychotropics, through their antimicrobial effect, have the potential to alter the human gut microbiota composition and metabolism, while probiotics can mitigate the related dysbiosis. The present research provides new insights into the existing interplay between psychotropic chemicals and gut microbiota, while further investigations are in progress.
- Ait Chait Y., Mottawea W., Tompkins T.A., Hammami R*. (2021) Nutritional and therapeutic approaches for protecting human gut microbiota from psychotropic treatments. Progress in Neuropsychopharmacology & Biological Psychiatry 108:110182.
- Ait Chait Y., Mottawea W., Tompkins T.A., Hammami R*. (2020) Unravelling the Antimicrobial side of antidepressants on gut commensal microbes. Scientific reports 10(1):17878.
III. Probiotics, Prebiotics, and Postbiotics for positive modulation of the gut microbiota and the host
At the NuGUT Research Platform, which focuses on nutrition-gut interactions, we employ an ex-vivo continuous fermentation model that simulates the human colon to assess the effect of different dietary formulations on microbiota structure functionality. There is a need to understand the chain of events linking food properties and composition, mainly probiotics and dietary fibers, with their effects on host health via the gut microbiota. Our research also explores extracellular vesicles production as a pathway mechanism by which microbiota interact with the gut–brain axis, as well as it is potential to restore dysbiotic gut microbiota, reach the systemic circulation, and deliver host-modulating metabolites in the brain to promote antidepressant effects. Our funded research also aims to develop an integrated nutritional approach based on the use of bacteriocinogenic bacteria for the positive modulation of the gut microbiota while reducing the vertical incidence of foodborne pathogens (such as Salmonella and Campylobacter) in animals.
- Sultan S., Mottawea W., Yeo J., and Hammami R*. (2021) Gut microbiota extracellular vesicles as signaling molecules mediating host-microbiota communications. Int. J. Mol. Sci. 22(23):13166.
- Mottawea W., Sultan S.*, Landau K., Bordenave N., Hammami R*. (2020) Evaluation of the prebiotic potential of a commercial synbiotic food ingredient on gut microbiota in an ex vivo model of the human colon. Nutrients 12(9):2669.
- Lone A., Mottawea W., Mehdi Y., and Hammami R*. (2021) Bacteriocinogenic probiotics as an integrated alternative to antibiotics in chicken production - why and how? Crit. Rev. Food Sci. Nutr. 1–17.
- Lone A., Mottawea W., Ait Chait Y., Hammami R*.(2021) Dual inhibition of Salmonella enterica and Clostridium perfringens by new probiotic candidates isolated from chicken intestinal mucosa. Microorganisms. 9(1):166.