Explanation: There are three notable common traits of bacteria, 1) lack of membrane-bound organelles, 2) unicellular and 3) small (usually microscopic) size. Not all prokaryotes are bacteria, some are archaea, which although they share common physicals features to bacteria, are ancestrally different from bacteria.
There are three notable common traits in all bacterias. Yes, bacteria can be found inside and iutside the body. Yes, they have cell nuclei. Yes, they are single celled organisms.