<human>:  What is the difference between a virus and a bacteria?
<bot>: The main difference between a virus and a bacteria is that viruses are much smaller and are obligate parasites, meaning they require a host cell to survive and reproduce. Bacteria are single-celled, sessile organisms that can survive and reproduce on their own. Viruses also lack a cell membrane and instead rely on the host cell's membrane to contain their genetic material, while bacteria have a cell membrane that contains their genetic material.