Table 1. Examples of bacteria as potential modulators of the anti-PD-1 immunotherapy in cancer (their modulatory mechanisms and effects have to be further investigated).

Ref. – Reference(s).

Bacteria (Gut)	Effect	Ref.
Ruminococcaceae family	Higher abundance in responders to anti-PD-1 therapy (melanoma); also, higher diversity of bacteria observed	33
Faecalibacterium genus	Higher abundance in responders to anti-PD-1 therapy (melanoma); also, higher diversity of bacteria observed	33
Bifidobacterium longum and Bifidobacterium adolescentis	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29,30
Collinsella aerofaciens	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Enterococcus faecium	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Klebsiela pneumoniae	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Veillonella parvula	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Parabacteroides merdae	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Lactobacillus sp.	Higher abundance in responders to anti-PD-1 therapy (metastatic melanoma)	29
Akkermansia muciniphila	Higher abundance in responders to anti-PD-1 therapy (lung and kidney cancers); exposure to antibiotics decreases response	31
Ruminococcus obeum	Higher abundance in non-responders to anti-PD-1 therapy (metastatic melanoma)	29
Roseburia intestinalis	Higher abundance in non-responders to anti-PD-1 therapy (metastatic melanoma)	29