What structure separates a bacterium from the surrounding environment?
Actually, I’d say the first line of defense for a bacterium would be it’s cell wall. The cell membrane performs much like a sieve, allowing some things in and some things out, but it is a delicate structure that can be easily damaged. The cell wall not only protects the cell membrane from outside damage, but it also keeps the cell’s own internal pressure from bursting the cell membrane and emptying it’s contents into the surrounding environment.
