On the plasma membrane of some bacteria and fungi.

The coniteints of bacterial cells cain be reversibly pulled away. (plasmolyzed) from the wall by strong salt solutions. Bacterial "protoplasts''-living cells divested of their wallshrink or swell with changing concentrations of solutes in their environment and burst when this concentration falls below a critical level. These observations have long suggested that the cytoplasm of bacteria is covered by a selecttvely permeable plasma membrane.