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Molly Campbell (MC): Can you discuss what gut dysbiosis is, and the emerging data that suggests it may contribute to human diseases, particularly SCI?
Ahmed Zayed (AZ): Gut dysbiosis is a shift in the composition of the gut microbiome (that includes microbes, viruses and fungi) to a new, persistent and imbalanced state. This is problematic because the functions (or metabolic activities) served by these microorganisms get disrupted, resulting in several documented human disorders, including immune dysfunction and several metabolic diseases that are also caused by SCI. This “concerted action” from the injury and the microbiome, including a positive feedback loop from the gut–spinal cord-brain axis, can exacerbate the condition of people with a SCI.
MC: You found that, after SCI, the number of “beneficial” bacterium decreased. Firstly, what makes a bacterium “beneficial”, and secondly, how did you measure these decreases?
AZ: Beneficial bacteria provide a health benefit to their hosts. For example, many microbes in our gut provide us with vitamins and other metabolites that can be of great benefit to both the immediate gut environment and to distal places such as the brain and the spinal cord. In our study, we found new microbial species, that were capable of making important metabolites (such as tryptophan and vitamin B6) that both support the integrity and motility of the gut and are required for the biosynthesis of neuroactive compounds essential for the health of our central nervous system. We tracked the relative abundance of these microbes, by quantifying the number of metagenomic reads that belong to them, and found that they significantly constitute less of the microbial community in the mice with SCI.