In Which Type of Bacteria is the Outermost Layer of the Cell

Question

In which type of bacteria is the outermost layer of the cell a thick wall of peptidoglycan?  
A) Proteobacteria
B) Cyanobacteria
C) Gram-positive bacteria
D) Gram-negative bacteria
E) Chlamydias

Accepted Answer

Gram-positive bacteria have a thick peptidoglycan layer in their cell wall, which makes them stain purple with crystal violet in the Gram stain. This distinguishes them from Gram-negative bacteria, which have a thinner layer of peptidoglycan and an outer membrane that stains pink with safranin in the Gram stain.