1. Antibiotic Use: Overuse or misuse of antibiotics can disrupt the balance of gut microbiota. 2. Diet: High-fat, high-sugar diets can negatively impact microbial diversity. 3. Stress: Chronic stress has been shown to alter gut bacteria. 4. Infections: Gastrointestinal infections can cause long-term changes in the microbiome. 5. Environmental Factors: Pollution and other environmental toxins can also contribute.