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NEST2026BiologyBiological Classification

Bacteria have cell wall made of a polymer of N-acetylglucosamine and N-acetylmuramic acid connected by -1,4 glycosidic bonds. Lysozyme, an enzyme, cleaves the glycosidic bond and disrupts the cell wall structure. In an experiment, Gram-positive and Gram-negative bacteria, which differ in terms of cell envelope and peptidoglycan thickness, are treated with lysozyme and subsequently placed in a hypotonic solution. The

Options

  1. AOnly Gram-negative bacteria are lysed.
  2. BGram-positive bacteria are lysed, but not Gram-negative bacteria.
  3. CBoth Gram-positive and Gram-negative bacteria are lysed.
  4. DNeither Gram-positive nor Gram-negative bacteria are lysed.

Correct answer

B. Gram-positive bacteria are lysed, but not Gram-negative bacteria.

Step-by-step solution

Gram-positive bacteria have a thick peptidoglycan layer that is directly exposed to the external environment. Lysozyme easily accesses and cleaves the -1,4 glycosidic bonds in their peptidoglycan, destroying the cell wall. When these cells are subsequently placed in a hypotonic solution, water enters the cells due to endosmosis, causing them to swell and lyse. Gram-negative bacteria possess an outer membrane composed of lipopolysaccharides and proteins that surrounds their thin peptidoglycan layer. This outer membr

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