Table 3.

Balance of protective and potentially aggressive resident intestinal bacteria and metabolites.

Protective	Potentially aggressive
Bacterial groups
Bacteroides species (B. fragilis, B. vulgatus)	Enterobacteriaceae (E. coli, Klebsiella pneumonia)
Clostridium species (select members of groups IV, XIVa, XVIII)	Ruminococcus gnavus
Lachnospiraceae	Enterococcus faecalis
Faecalibacterium prausnitzii	Fusobacterium species (F. varium, F. nucleatum)
Lactobacillus species (L. reuteri)
Bacterial metabolites or substrates
SCFA (butyrate, propionate, pentenoate)	↓SCFA
Indoles	Hydrogen sulfide
Sphingolipids	Sulfated bile acids
Secondary bile acids	Primary bile acids
	Ethanolamine
	Iron