The cell wall Gram-positive Gram-negative outer membrane mermbrane outside of cell membrane cytoplasm cytoplasm rigid, protecting cell Hans Christian Gram from osmotic lysis periplasmic space peptidoglycan Gram staining 1884 Gram Positive Gram NegativeThe Cell Wall Gram Positive Gram Negative 1884 Hans Christian Gram - outside of cell membrane - rigid, protecting cell from osmotic lysis Gram staining