Question

You need to determine if a pure culture of bacteria is gram-positive or gram-negative, but you've just spilled your only solution of crystal violet so you can't do a Gram stain. You decide to try a lysozyme treatment on a sample of each culture and then examine the samples under the microscope. The expected result is?

Answer 1

Gram positive bacteria will be lysed whereas gram negative bacteria will be unaffected.

Step-by-step explanation:

• Lysozyme treatment degrades bacterial cell wall. It destroys the peptidoglycan cell wall by hydrolyzing the glycosidic bond between NAM and NAG sugar residues present in the cell wall.
• Gram positive bacteria has a thick peptidoglycan cell wall with only a thin outer layer of techoic acid. So when exposed to lysozyme, the peptidoglycan layer disintegrates and forms debris.
• Gram negative bacteria has a thin peptidoglycan cell wall and a tough outer membrane. The outer membrane does not allow the lysozyme to come in contact with the cell wall keeping it intact.
• Hence, Gram positive bacteria will be lysed whereas gram negative bacteria will be unaffected by lysozyme treatment.