Fig. 5

Microbial therapies for Parkinson’s disease. a Probiotics, prebiotics, synbiotics, and fecal microbiota transplantation are the most commonly used microbial therapies for PD. These therapies can be administered through oral, nasogastric, rectal, or colonoscopic route. b Microbial therapies have neuroprotective effects on the brain by reducing the blood–brain barrier damage, decreasing microglial and astrocytic activation, suppressing neuroinflammation, and inhibiting α-syn aggregation, thereby preventing the death of dopaminergic neurons. c In the gut, microbial therapies can regulate gut microbes, improve intestinal metabolism, modulate the intestinal mucosal immune system, inhibit gut inflammation, and restore gut barrier damage, resulting in improved intestinal symptoms. d In conclusion, microbial therapies relieve nonmotor symptoms of PD, particularly constipation, as well as the motor symptoms through multiple pathways