Table 1.

A comparative synthesis of acute and environmental stressors, associated gut microbiome alterations, and functional implications. It integrates evidence across physiological, occupational and extreme environments to highlight cross-domain resilience mechanisms and translational opportunities.

Stressor category	Representative context	Microbiome alterations (comparative synthesis)	Functional and metabolic implications	Potential resilience or mitigation strategies
Circadian disruption and sleep loss	Human and rodent models of jetlag or sleep restriction	Reduced microbial diversity and beneficial taxa (Lactobacillaceae); altered Firmicutes/Bacteroidetes ratio; disrupted rhythmicity of bacterial metabolism	Perturbation of short-chain fatty acid (SCFA) and bile acid pathways; mitochondrial and metabolic dysregulation	Restoration of SCFA-producing taxa through prebiotic or timed feeding interventions improves circadian alignment and host resilience
Psychological and physical stress	Military and occupational training, high workload	Loss of beneficial genera such as Bifidobacterium and enrichment of proinflammatory taxa	HPA axis overactivation, reduced microbial metabolites linked to stress buffering	Synbiotic formulations combining Lactobacillus acidophilus, Bifidobacterium animalis and inulin improved physiological and cognitive outcomes
Thermal and environmental stress	Heat acclimation and cold exposure in animal and human studies	Selective expansion of probiotic species (Lactobacillus, Bifidobacterium); reduction of opportunistic pathogens	Enhanced thermotolerance and immune stability under temperature variation	Thermal acclimation and nutritional support promote microbiome-mediated adaptation
Hypobaric hypoxia (high altitude)	Mountaineering and hypoxia chamber exposure	Increase in proinflammatory bacteria; depletion of anaerobic commensals	Inflammation, oxidative stress and impaired gastrointestinal integrity	Glutamine and antioxidant supplementation support microbial balance and barrier function
Infectious stressors (travelers’ diarrhea)	Enterotoxigenic Escherichia coli, Shigella and Campylobacter exposure	Transient dysbiosis, reduction of protective taxa and overgrowth of pathogens	Gut barrier disruption, systemic inflammation and reduced nutrient absorption	Galacto-oligosaccharide supplementation and probiotic therapy shown to reduce diarrhea incidence and restore microbiota
Spaceflight and microgravity	Astronauts (International Space Station, MARS500) and hindlimb unloading models	Reduced microbial diversity, altered abundance of Parasutterella and Akkermansia, increased Firmicutes	Dysregulated immunity and glucose metabolism, enhanced oxidative stress	Probiotic supplementation and crocodile gut-derived bacterial metabolites shown to mitigate dysbiosis in simulated microgravity
Hardy species and adaptive microbiomes	Crocodylus and Varanus species	Presence of stress-tolerant microbes and producers of bioactive metabolites such as leucrocin, cathelicidin and hepcidin	Potential for antimicrobial, anti-inflammatory and epigenetic modulation via secondary metabolites	Isolation and characterization of microbial metabolites for translational probiotic applications
Dietary and nutritional modulation	High-fat or low-fiber diets, malnutrition	Reduced SCFA-producing taxa and overall microbial diversity	Disturbed nutrient metabolism, immune dysregulation and inflammation	Fiber-rich and prebiotic diets restore microbial homeostasis and support physiological resilience