Instructions: Given a text passage, come up with an appropriate title for it. The title should accurately represent what the main focus of the passage is. The title of a passage may be present in the first few sentences of the passage and/or be referred to multiple times in the passage. The title should be 1-5 words long.
Input: Gram staining differentiates bacteria by the chemical and physical properties of their cell walls by detecting peptidoglycan , which is present in the cell wall of Gram - positive bacteria . Gram - negative cells also contain peptidoglycan , but a very small layer of it that is dissolved when the alcohol is added . This is why the cell loses its initial colour from the primary stain . Gram - positive bacteria retain the crystal violet dye , and thus are stained violet , while the Gram - negative bacteria do not ; after washing , a counterstain is added ( commonly safranin or fuchsine ) that will stain these Gram - negative bacteria a pink color . Both Gram - positive bacteria and Gram - negative bacteria pick up the counterstain . The counterstain , however , is unseen on Gram - positive bacteria because of the darker crystal violet stain .
Output:
Gram stain