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

Table 1 Gut bacteria and their mechanisms of involvement in various disorders

Sl No.	Disease	Mechanism of involvement	Key bacteria implicated	Ref.
1	Alzheimer’s disease	Gut microbiota influences neuroinflammation and cognitive function; modulation of SCFA production affects brain health	Lactobacillus spp., Bifidobacterium spp.	[32]
2	Anxiety and depression	Dysbiosis, inflammation, cytokine release, HPA axis dysregulation	Bifidobacterium, Lactobacillus	[33]
3	Anxiety disorders	Gut microbiota-induced alterations in neurotransmitter levels and stress response pathways; modulation of vagus nerve activity	Campylobacter jejuni, Lactobacillus rhamnosus	[34]
4	Autism spectrum disorders	Interaction between Candida albicans and bacterial metabolites	Candida albicans	[35]
		Changes in gut microbiota affecting neurodevelopment and behavior; disruption in SCFA metabolism affecting microglial function	Bacteroides spp., Firmicutes spp.	[36]
5	Cognitive impairment	Gut microbiota affecting cognitive control and executive function networks such as the FPN and DMN	Bacteroides, Prevotella, Ruminococcus	[37]
6	Depression	Dysbiosis leading to increased intestinal permeability and systemic inflammation; alterations in serotonin and other neurotransmitter levels	Lactobacillus spp., Bifidobacterium spp.	[38]
		Chronic low-grade inflammation and altered neuroplasticity; influence on HPA axis and neurotransmitter metabolism	Lactobacillus spp., Bifidobacterium spp.	[39]
7	Emotional and interoceptive awareness	Gut microbiota composition associated with brain areas involved in emotional and visceral interoception	Roseburia, Bacteroides	[40]
8	Irritable bowel disease	Disruption in the balance of gut microbiota leads to chronic inflammation and dysbiosis affecting mood and stress responses	Faecalibacterium prausnitzii, Bacteroides spp.	[41]
9	Irritable bowel syndrome	Gut microbiota-induced inflammation and dysregulation of the enteric nervous system; alterations in gut motility and visceral hypersensitivity	Bifidobacterium spp., Lactobacillus spp.	[42]
10	Mood disorders	Alterations in gut-brain communication affecting mood-related brain networks	Bifidobacterium, Collinsella	[43]
11	Neurological disorders	Influence on neuroinflammation, gut-brain axis communication	Lactobacillus, Bacteroides	[44]

SCFA: Short-chain fatty acid; HPA: Hypothalamic-pituitary-adrenal; FPN: Frontoparietal network; DMN: Default mode network.