Table 1.

General composition of animal gut microbiota.

Domain/Phylum	Description	Examples	Importance
Bacteria	Most abundant	Bacillota (Clostridiales, Lactobacillales), Bacteroidetes (Bacteroides, Prevotella), Proteobacteria (Escherichia, Salmonella), Actinobacteria (Bifidobacterium)	Digestion, nutrient fermentation, immune modulation, pathogen inhibition
Archaea	Less abundant	Methanogens	Methane production in ruminants
Eukarya (Mycobiota)	Fungi (yeasts, molds)	Candida, Saccharomyces	Gut health
Eukarya (Protista)	Commen-sal or parasitic	Entodinium (ciliate protozoa)	Cellulose digestion (herbivores)
Viruses	Abundant	Bacteriophages, eukaryotic viruses	Regulate bacterial populations