As we know, autoimmune destruction of a key process of manufacturing GABA is implicated in the severe spasticity seen in SPS. Here is a new article on basic research done on the fecal bacteria content of normal people and its relationship with GABA levels found in those people. In this article, authors mention Major Depression as a result of low GABA and disturbed gut microbiota. The same would be said for SPS, making fecal transplant or other treatment of the fecal microbiota a good avenue for research and treatment. They are already doing research on MS with some preliminary good findings.

GABA-modulating bacteria of the human gut microbiota
Philip Strandwitz, Ki Hyun Kim, Darya Terekhova, Joanne K. Liu, Anukriti Sharma, Jennifer Levering, Daniel McDonald, David Dietrich, Timothy R. Ramadhar, Asama Lekbua, Nader Mroue, Conor Liston, Eric J. Stewart, Marc J. Dubin, Karsten Zengler, Rob Knight, Jack A. Gilbert, Jon Clardy & Kim Lewis
Nature Microbiology



The gut microbiota affects many important host functions, including the immune response and the nervous system1. However, while substantial progress has been made in growing diverse microorganisms of the microbiota2, 23–65% of species residing in the human gut remain uncultured3,4, which is an obstacle for understanding their biological roles. A likely reason for this unculturability is the absence in artificial media of key growth factors that are provided by neighbouring bacteria in situ5,6.

In the present study, we used co-culture to isolate KLE1738, which required the presence of Bacteroides fragilis to grow. Bioassay-driven purification of B. fragilis supernatant led to the isolation of the growth factor, which, surprisingly, is the major inhibitory neurotransmitter GABA (γ-aminobutyric acid). GABA was the only tested nutrient that supported the growth of KLE1738, and a genome analysis supported a GABA-dependent metabolism mechanism.

Using growth of KLE1738 as an indicator, we isolated a variety of GABA-producing bacteria, and found that Bacteroides ssp. produced large quantities of GABA. Genome-based metabolic modelling of the human gut microbiota revealed multiple genera with the predicted capability to produce or consume GABA.

A transcriptome analysis of human stool samples from healthy individuals showed that GABA-producing pathways are actively expressed by Bacteroides, Parabacteroides and Escherichia species. By coupling 16S ribosmal RNA sequencing with functional magentic resonance imaging in patients with major depressive disorder, a disease associated with an altered GABA-mediated response, we found that the relative abundance levels of faecal Bacteroides are negatively correlated with brain signatures associated with depression.”