One of my postdoc research grants for some 3 years was gut microbiota effects on aging. During that time I have read so many articles providing conclusive data about the guy microbiota affecting your appetite, dietary choices, mood, cancer resistance, immune system, types of immune responses, amount of inflammation or even sleep patterns.

The details go as far as to discuss the combined effects of different bacteria/microbes in general vs single strains, and whether or not they are fre floating in the lumen on the intestines or are adhered to the intestinal wall.

All the details mentioned have certain effects on the features and properties of all the microbes.