Microbiologists use the Gram stain to aid in identification of bacteria. What is the major difference between Gram- positive and Gram- negative bacteria?
A) presence or absence of muramic acid in the cell wall
B) presence or absence of peptidoglycan in the cell wall
C) presence or absence of outer membrane
D) structure of the lipids in the plasma membrane

Question

Quizplus · Accepted Answer

The major difference between Gram-positive and Gram-negative bacteria is the presence or absence of an outer membrane. Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane while Gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane containing lipopolysaccharides. The presence of this outer membrane affects the binding of the crystal violet and safranin dyes used in the Gram stain, resulting in different colors for the two types of bacteria.

Microbiologists Use the Gram Stain to Aid in Identification of Bacteria