Gram staining differentiates bacteria based on:

A) Size only

B) Cell wall structure — gram-positive bacteria retain crystal violet dye due to thick peptidoglycan layer

C) Motility

D) Spore formation

Explanation

Gram stain: crystal violet + iodine → decolorize → safranin. Gram+: thick peptidoglycan retains crystal violet (purple). Gram-: thin peptidoglycan, outer membrane, loses crystal violet, takes safranin (pink).

Practice More Everyday Science Questions