Table 1.

Involvements of gut microbiota in neurodegenerative disease.

Bacterial genus	Possible involvements	Related neurodegenerative diseases	Reference
Escherichia, Pseudomonas, Staphylococcus, Streptococcus, Bacillus, Mycobacteria, Citrobacter, Klebsiella, Salmonella	Bacterial amyloid, FapCs, Translocate across BBB through GBA	Alzheimer’s disease	Cao et al. (84)
Lactobacillus	GABA, Balance the regulation of cortical excitability and neural excitation-inhibition	Alzheimer’s disease	Ciminelli et al. (85) Auger et al. (86)
Bifidobacterium	GABA, Balance the regulation of cortical excitability and neural excitation-inhibition	Alzheimer’s disease	Auger et al. (86)
Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Lachnospiracea	Unknown	Alzheimer’s disease	Vogt et al. (87) Zhuang et al. (88) Ling et al. (89)
Roseburia, Faecalibacterium	Can produce SCFAs	Parkinson’s disease	Nuzum et al. (90)
Pseudomonas	Fap, change of α-synuclein	Parkinson’s disease	Christensen et al. (91)
Enterobacteriaceae	Curli, α-synuclein aggregation	Parkinson’s disease	Sampson et al. (92)
Clostridium coccoides, Bacteroides fragilis, Prevotellaceae	Unknown	Parkinson’s disease	Hopfner et al. (93) Hasegawa et al. (94) Scheperjans et al. (95)
Hydrogen-product bacteria	Reduced dopaminergic loss	Parkinson’s disease	Fujita et al. (96) Yorikata et al. (97) Guo et al. (98)
Coriobacteriales, Erysipelotrichales, Bacteroidales, Burkholderiale	Unknown	Huntingdon disease	Kong et al. (99) Radulescu et al. (100)
Clostridium	Decrease level of SCFA secretion	Multiple sclerosis	Miyake et al. (101)
Firmicutes, Bacteroidetes, Prevotella	Unknown	Multiple sclerosis	Cosorich et al. (102) Chen et al. (103)

BBB, blood–brain barrier; GBA, gut–brain axis; GABA, gamma-aminobutyric acid; SCFA, short-chain fatty acid.