Unlocking the secrets of the human gut microbiota: Comprehensive review on its role in different diseases

Table 2 Microbiota-associated mechanisms in autoimmune and inflammatory diseases: Insights and implications

Sl No.	Disease	Mechanism of involvement	Key bacteria implicated	Ref.
1	Allergies	Modulation of immune responses, allergic inflammation	Clostridium, Bifidobacterium	[49]
2	Autoimmune diseases	Dysregulated immune responses, inflammation	Prevotella, Bacteroides	[50]
3	Cardiovascular diseases	Production of trimethylamine N-oxide, systemic inflammation	Prevotella, Firmicutes	[51]
4	Inflammatory bowel disease	Dysregulated immune responses against microbiota lead to chronic inflammation in the GI tract. Reduced anti-inflammatory microbes and increased potentially inflammatory microbes. SCFAs and dietary factors influence disease progression	Decreased Bacteroidetes, Lachnospiraceae, Faecalibacterium prausnitzii. Increased Proteobacteria, Ruminococcus gnavus. Key producers: Faecalibacterium prausnitzii, Roseburia hominis. Pathogens: Vancomycin-resistant Enterococcus	[52]
		Associated with reduced anti-inflammatory response. Increased pro-inflammatory activity	Reduced abundance of Faecalibacterium prausnitzii. Overgrowth of Escherichia coli	[53]
5	Liver diseases	Regulation of bile acid metabolism, inflammation	Enterococcus, Ruminococcus	[54]
6	Multiple sclerosis	Microbiota interaction: Dysbiosis with increased Euryarchaeota and Verrucomicrobia. Microbial impact: Modulation of T cell responses and inflammation in the central nervous system. Protective effects: Certain bacteria and metabolites have protective effects against disease	Increased: Methanobrevibacter smithii, Akkermansia muciniphila. Decreased: Clostridia clusters XIVa and IV, Bacteroidetes. Protective: Lactobacillus reuteri, Lactobacillus murinus	[55]
		Akkermansia muciniphila and Acinetobacter calcoaceticus induce pro-inflammatory responses. Parabacteroides distasonis stimulates anti-inflammatory Tregs	Decreased abundance of Lachnospiraceae and Faecalibacterium. Increased abundance of Akkermansia spp.	[56]
7	Respiratory infections	Modulation of respiratory immune responses, inflammation	Streptococcus, Haemophilus	[57]
8	Rheumatoid arthritis	Dysbiosis contributes to systemic inflammation and joint symptoms; gut barrier dysfunction affecting overall immune response	Prevotella spp., Fusobacterium spp.	[58]
		Microbiota interaction: Oral and intestinal dysbiosis linked to disease severity and immune responses. Microbiota influence: Microbial DNA and peptidoglycan-polysaccharide complexes found in joints. Microbial-induced immunity: Certain bacteria drive inflammation through immune cell activation	Oral dysbiosis: Porphyromonas gingivalis, Lactobacillus salivarius. Intestinal dysbiosis: Increased Gram-positive bacteria, Prevotella copri. Exacerbation: Prevotella copri, Segmented filamentous bacteria	[59]
		Pro-inflammatory molecule production. Autoreactive immune cell activation. Linked to RA susceptibility with specific HLA-DRB1 alleles	Overgrowth of Prevotella spp., reduction in Bacteroides, Bifidobacterium, butyrate-producing bacteria, and high abundance of Ruminococcus gnavus	[60]
9	Systemic lupus erythematosus	Microbiota interaction: Dysbiosis in oral and gut microbiota contributes to disease through molecular mimicry and bacterial antigen recognition. Metabolic factors: Bacterial metabolites impact disease severity	Increased: Lactobacillaceae, Ruminococcus gnavus. Decreased: Bifidobacteria, Clostridiales. Specific antigens: Propionibacterium propionicum, Bacteroides thetaiotaomicron	[61]

SCFA: Short-chain fatty acid; GI: Gastrointestinal; Treg: Regulatory T cell.