TABLE 1.

Phyla Identified in Infant Gut

Phylum	Class	Genus examples	Species examples	Characteristics
Actinobacteria	Actinobacteria	Bifidobacterium	B. longum B. breve B. bifidum	Gram positive Branched rod-shaped Obligate anaerobe Lactic acid producer Able to use non-digestible plant polymers for energy
		Atopobium	Atopobium spp.	Gram positive Cocci or rod-shaped Facultative anaerobe Lactic acid producer
		Corynebacterium	Corynebacterium spp.	Gram positive Rod-shaped Aerobic or facultatively anaerobic Lactic acid producer under certain conditions
		Propionibacterium	Propinobacterium spp.	Gram positive Rod-shaped Anaerobic Lactic acid, propionic acid or acetic acid from glucose
Bacteroidetes	Bacteroidetes	Bacteroides	B. fragilis B. vulgatus	Gram negative Rod-shaped Obligate anaerobe Assist in food breakdown and production of valuable nutrients and energy
		Prevotella	Prevotella spp.	Gram negative Rod-shaped Obligate anaerobe
Firmicutes	Bacilli	Lactobacillus	L. acidophilus L. delbrueckii L. rhamnosus	Gram positive Rod-shaped Facultative anaerobes Lactic acid producer
		Enterococcus	E. Faecalis	Gram positive Cocci occurring singly, pairs or short chains Facultative anaerobe
		Clostridium	C. perfringens C. difficile C. paraputrifium	Gram positive Rod shaped Obligate anaerobe Toxin producers
		Ruminococcus	Ruminococcus spp.	Gram positive Coccoid shape Obligate anaerobe Breaks down cellulose, glucose, and xylose
		Streptococcus	S. intermedius S. mitis S. salivaris	Gram positive Spherical occurring in pairs or chains Facultative or obligate anaerobes
		Staphylococcus	S. Epidermidis	Gram positive Cocci in grape-like clusters Facultative anaerobes
	Clostridia	Escherichia	E. Coli	Gram negative Rod-shaped Facultative anaerobes
		Klebsiella	K. oxytoca	Gram negative Rod-shaped Facultative anaerobes
Proteobacteria	Gammaproteobacteria	Enterobacter	Enterobacter spp.	Gram negative Rod-shaped Facultative anaerobes Ferment both glucose and lactose