Table 2.

The predominant bacterial phyla of the human body

Bacterial phylum	Class	Example	Body location	Characteristics	References
Actinobacteria	Acidimicrobiia, Actinobacteria, Coriobacteriia, Rubrobacteria, Thermoleophilia, Nitriliruptoria	Corynebacterium, Mycobacterium, Nocardia, Bifidobacterium, Streptomyces	Intestine, oral cavity, skin	Gram-positive, filamentous, physiologically aerobic, they can be heterotrophic or chemoautotrophic, but most are chemoheterotrophic and able to use a wide variety of nutritional sources	Donova (2007), Barka et al. (2016)
Bacteroidetes	Bacteroidia, Flavobacteria, Sphingobacteria	Bacteroides, Prevotella	Intestine, oral cavity	Aerobic and anaerobic, non-spore-forming, Gram-negative rods	Wexler (2007), Gupta (2004)
Firmicutes	Bacilli, Clostridia, Erysipaelotrichia, Thermolithobacteria, Negativicutes	Clostridium, Staphylococcus, Enterococcus, Lactobacillus spp	Intestine, skin, stomach	Gram-positive, rod, coccoid, spiral in shape, anaerobic, aerobic, include commensal and beneficial bacteria	Zhuang et al. (2019), Reichmann and Gründling (2011)
Proteobacteria	Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria Deltaproteobacteria, Epsilonproteobacteria	Escherichia, Salmonella, Vibrio, Helicobacter, Yersinia, Legionellales	Large intestine, skin	Gram-negative bacteria	Kersters et al. (2006)