Table 5.

Some examples of potentially harmful gut microbiota bacterial species

Bacteria	Associated physiologic changes	Associated diseases states
Bacteroides	Activate CD4+ T cells	Increased with animal-based diet; Increased in obesity
Bilophila	Promote pro-inflammatory immunity	Increased in colitis; Decreased in autism
Clostridium	Promote generation Th17 cells	Increased after smoke exposure; Increased in autism and Rett syndrome; Positive correlation with plasma insulin and weight gain; Increased in type 2 diabetes; Clostridium perfrigens increased in old age
Escherichia coli	TLR activation	Increased in inflammatory bowel disease; Increased in type 2 diabetes
Neisseria	Sugar fermentation	Only two species are pathogenic: Neisseria meningitides and Neisseria gonorrhoeae

Th17: T helper 17: TLR: Toll-like receptor.