Researchers had the idea of feeding cats a "moderate carbohydrate" diet to see what would happen to their gut microbiome. They found that cats fed on this diet had a higher level of saccharolytic bacteria and lower levels of proteolytic bacteria -- unsurprisingly.

Here's where it gets interesting. "Live Science" reporting this headlines the story:

High-protein diet not so good for kitty's belly, study suggest
The study seems to have suggested nothing of the sort.

Further, "Live Science" gushes:

“Surprisingly, kittens eating the higher-carb kibble had more of the beneficial gut bacteria bifidobacterium. Low levels of bifidobacteria have been linked to irritable bowel syndrome in humans. Compared with the other groups of kitties, the high carb-eating kittens also had higher levels of lactobacillus, beneficial bacteria that may play a role in cholesterol and appetite regulation.”*
http://www.livescience.com/24174-h

Haven't located the study at the BMJ yet, but what you find elsewhere on the net is interesting and revealing.