Table 1.

Overview of selected bacteria and their impact on gut and brain function.

Bacteria	Effects on Intestines	Effects on the CNS
Bifidobacterium breve	Regulation of the gut microbiota composition [123].	Positive impacts on cognitive function, neuroprotective effect, and improvement of synaptic plasticity [123,124].
Lactic acid bacteria (LAB)	Inhibition of gut pathogenic bacteria, maintenance of gut barrier integrity, and homeostasis [125]. Regeneration of epithelial cells [126].	Reduction in neuroinflammation [127].
Lactobacillaceae and Bifidobacterium	Enhancement of the integrity of the intestinal epithelial barrier by increasing the levels of junction proteins and beneficially influencing the gut microbiota [128].	Improvement in memory and regulation of emotional behaviors by increasing the level of GABA in the hippocampus and regulation of central GABA receptor expression [129,130].
Lactobacillus	Lactobacillus plantarum 299v and Lactobacillus rhamnosus GG suppress inflammation and protect against intestinal barrier damage through regulatory effects on LPS-mediated cytotoxic activity in intestinal epithelial cells [131].	Lactobacillus plantarum 299v supports selective serotonin reuptake inhibitors (SSRIs) treatment, resulting in improved cognitive function and decreased kynurenine levels [132].
Escherichia coli Nissle 1917	Regulation of gut microbiota composition and amelioration of colonic barrier function [133,134].	Reduction in the severity of experimental autoimmune encephalomyelitis (EAE) connected with modulation of the inflammatory response of CD4+ T cells, their migration to the CNS, and restoration of the intestinal barrier integrity [135]. Neuroprotection, improvement in motor deficits, and reduction in brain inflammation [134]. Reductive impact on anxiety-like behaviors [133].
Akkermansia muciniphila	Acceleration of intestinal stem cell proliferation and cell differentiation in the gut [136]. Activation of NF-κB in intestinal cells, enhancement of barrier function and immune responses [137]. Reduction in the severity of acute colitis symptoms and inflammation [138].	Inhibition of inflammatory cytokines in microglial cells [139]. Reduction in depressive-like behaviors and modulation of gut serotonin dynamics in mice [75].
Roseburia hominis	Immunomodulation [140].	Reduction in neuroinflammation via histone deacetylase inhibition [141].
Clostridium butyricum	Protection of the gut barrier integrity, a decrease in the levels of D-lactate in plasma and IL-6 in the colon, and up-regulation of occludin expression [142].	Neuroprotective effects against neurological dysfunction, brain edema, neurodegeneration, and BBB disruption [142].
Faecalibacterium prausnitzii	Enhancement in intestinal cell health and reduction in inflammation [143]. Improvement in gut barrier integrity [144,145].	Improvement in cognitive impairment in a mouse model of Alzheimer’s disease [146].