That is the title of a recent paper on the human gut microbiome.

The researchers compare the effects of plant vs animal-based diets on a range of metrics including bile acids, bacteria and viruses.

Here is one of their main conclusions:

we show that the short-term consumption of diets composed entirely of animal or plant products alters microbial community structure and overwhelms inter-individual differences in microbial gene expression.

Also of note:

increases in the abundance and activity of Bilophila wadsworthia on the animal-based diet support a link between dietary fat, bile acids and the outgrowth of microorganisms capable of triggering inflammatory bowel disease

Larger studies in this area would be useful, however there are some very interesting preliminary results here.

Particularly fascinating is the ability of the gut to adapt to new diets. A complex topic to say the least.

Here is the link to the full paper