1. are unicellular organisms that lack a nucleus 2. A second membrane, called the , is found outside the wall in some bacteria.

3. are the most rare of the two different domains of prokaryotes, and are found primarily is harsh conditions.

4. The protective structure that a prokaryote may form when conditions are unfavorable is called an

5. Bacterial growth can be slowed or blocked using medications called .

6. Bacteria can connect and exchange pieces of DNA, called plasmids, through a process known as .