What is a shared characteristic of both bacteria and archaea?

Both bacteria and archaea share the characteristic of having free-floating DNA in the nucleoid region. This is a fundamental feature of prokaryotic cells, which do not have a true nucleus. Instead, their genetic material is located in a region called the nucleoid, where it is not enclosed by a membrane.

This shared characteristic highlights a key difference between prokaryotes, such as bacteria and archaea, and eukaryotes, which have organized nuclei and more complex cellular structures. In contrast, options like the presence of a nucleus and complex membrane-bound organelles are features exclusive to eukaryotic cells. Similarly, mitochondria are specific to certain eukaryotic cells and are not found in either bacteria or archaea. Thus, the free-floating DNA in the nucleoid region is indeed a defining characteristic of both bacterial and archaeal cells.