This is the space inbetween the peptidoglycan and the outer membrane which contains many different proteins. These proteins fucntion to detect the environment and transport needed nutrients into the cell. To protect themselve, bacteria synthesize small molecules to balance the osmotic stress. These are called compatible solutes. For most bacterial cells, the cell wall is critical to cell survival, yet there are some bacterial cells which do not have cell walls.
Mycoplasma species are one example and they are very wide spread.
Some of this dependency is based on the lack of cell walls. As an example, they are quickly killed if placed in an environment with very high or very low salt concentrations. Due to the lack of a cell wall, Mycoplasma have unusually tough membranes that are more resistant to rupture than other bacteria. The presence of sterols in the membrane contribute to their durability. These forms may result from partial or complete loss of the cell wall.