üherakuliste elusorganismide grupp, kuhu kuuluvad bakterid (eubakterid) ja arhead, kellel puuduvad membraaniga ümbritsetud tuum ja organellid, A prokaryote is a unicellular organism that lacks a membrane-bound nucleus (karyon), mitochondria, or any other membrane-bound organelle. Prokaryotes can be divided into two domains, archaea and bacteria. In contrast, species with nuclei and organelles are placed in the domain Eukaryota.