This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
Action of lysozymes on gram negative bacteria ? 
Select and explain. 
A. Faster than gram positive bacteria, B. Has no action, C. Depends on integrity of outer membrane, D. Cause resistance to antibiotic
C: Depends on integrity of outer membrane
Answer: C: Depends on integrity of outer membrane 
Explanation: Ans. is 'c' i.e., Depends on integrity of outer membrane Lysozyme is an acetyl - mura midase which cleaves bond between N-acetylmuramic acid and N-acetyl - D-glucosamine residues in peptidoglycan of all wall.Gram-positive bacteria are sensitive to action of lysozymes -> lysozymes cause lysis of gram-positive bacteria easily.Gram-negative bacteria are less susceptible and are protected by outer membrane, which is the outer most covering in gram negative bacteria (outside the cell wall) and has barrier function.However, lysozyme can cleave the peptidoglycan layer of Gram-negative bacteria if this layer is exposed by membrane attack complex (MAC or C5-9) of complement which destroys outer membrane. (Note : gram positive bacteria do not have outer membrane thus lysozymes directly act on cell membrane).