system
Given the following post, respond as if you're commenting on Reddit:
human
[TheCulture] Culture humans use genetically modified bacteria to control their biology, why is that better than achieving the same thing via nano tech?
gpt
GM bacteria *are* nanotech, they're just 3D electromechanical, water-based, chemical difference engines... that self repair and reproduce.


Literally, they're nanotech that's carbon based, not silicon based.

Earth Humans have a very intimite (and still poorly understood) relationship with their microbiome.  Everything, from your taste in foods to sexual partners, is influenced by your microbiome - to the extent that if we just replaced yours with silicon nanobots it would be the equivalent of replacing a part of your brain with silicon - doable, but is it still *you*? 

The Culture decided to go via the microbiome route and not the 'nanobiome' route - possibly for the philisophical reasons, but also because you'll never actually escape bacteria (every human race they contact will have them, every flake of dust, every surface they touch...) so might as well roll with it and make it part of the plan, not a problem.