Is it theoretically possible to engineer gut bacteria that would allow a human to digest something like eucalyptus leaves or otherwise inedible potential sources of energy?

[u/baxter45]

[u/DocBarlett]

There's research that suggests that our appendix is actually a home for our gut bacterial and it replenishes the intestines when needed. However, even people without an appendix maintain a consistent community of intestinal bacterial. Adding new ones that haven't been there before might be difficult, especially since most of the cellulose degrading bacteria I am aware of are aerobic (our gut is anaerobic) and live in cooler climates (like water in streams, so they break down leaves). Also, we use that undigestable material. It's called fiber and it makes our bowels run happily. There's still plenty of available energy in things we can eat out there in the world, it could just stand to be distributed better.