What is a cell envelope? Do all bacteria have cell envelopes?

Ans : The cell envelope is the collective term used for the casing of the bacterial cell. It usually consists of the cell wall and the cell membrane. Sometimes Gram-negative bacteria may also include a layer covering the cell wall, thus being the outermost covering of the cell.

While most bacteria have cell envelopes some, like those of the Mollicute family, do not have cell envelopes.