<prompt> Peptidoglycans are found in large quantities in cell wall of: March 2009VirusGram positive bacteriaGram negative bacteriaAll of the above  <response>: Ans. B: Gram positive bacteria The Bacteria eubacteria, with the exception of the Chlamydias have a semirigid cell wall containing peptidoglycan. Gram negative bacterias peptidoglycan layer is much thinner than in Gram-positive bacteria In general, the walls of gram positive bacteria have a simpler chemical nature than those of gram negative bacteria. The mycoplasmas are the only bacteria that naturally lack a cell wall. Mycoplasmas maintain a nearly even pressure between the outside environment and the cytoplasm by actively pumping out sodium ions. Their cytoplasmic membranes also contain sterols that most likely provide added strength. All other bacteria have a cell wall Peptidoglycan prevents osmotic lysis. Under the cytoplasmic membrane, bacteria concentrate dissolved nutrients solute through active transpo. As a result, the bacteriums cytoplasm is usually hypeonic to its surrounding environment and the net flow of free water is into the bacterium. Without a strong cell wall, the bacterium would burst from the osmotic pressure of the water flowing into the cell. 