Gut microbiota

Background

• The gastrointestinal tract is normally colonized with a number of microbes
• Comprised of an estimated 35,000 bacterial species
• The gut flora are impacted by:
  • Mode of delivery at birth (Cesarean section versus vaginal delivery)
  • Diet during infancy (breast milk versus formula)
  • Diet during adulthood (plant-based or meat-based)
  • Use of antimicrobials
• May play a role in a number of diseases

Members

• A healthy gut microbiota is dominated by bacteria in the phyla Bacteroidetes or Firmicutes, followed by Actinobacteria and Verrucomicrobia
• Varies by location
  • Esophagus: Bacteroides, Gemella, Megasphaera, Pseudomonas, Prevotella, Rothia, Streptococcus, Veillonella
  • Stomach: Streptococcus, Lactobacillus, Prevotella, Enterococcus, Helicobacter pylori
  • Small intestine: Bacteroides, Clostridium, Streptococcus, Lactobacillus, Proteobacteria, Enterococcus
  • Cecum: Lachnospira, Roseburia, Butyrivibrio, Ruminococcus, Fecalibacterium, Fusobacterium
  • Colon: Bacteroides, Clostridium, Prevotella, Porphyromonas, Eubacterium, Ruminococcus, Streptococcus, Enterobacterium, Enterococcus, Lactobacillus, Peptostreptococcus, Fusobacterium

Further Reading

• Role of the normal gut microbiota. World J Gastroenterol. 2015;21(29):8787-803. doi: 10.3748/wjg.v21.i29.8787. PMID: 26269668; PMCID: PMC4528021.