Here's why:

* Bacteria are single-celled organisms belonging to the domain Bacteria. They have a simple cell structure without a nucleus or membrane-bound organelles.

* Fungi are eukaryotic organisms that belong to the Kingdom Fungi. They have a more complex cell structure with a nucleus and other organelles, and they typically obtain nutrients by absorbing them from their environment.

* Protists are a diverse group of eukaryotic organisms that are not fungi, plants, or animals. They are generally single-celled and can have various modes of nutrition.

E. coli, like all bacteria, falls into the domain Bacteria, making it distinct from fungi and protists.