Microbiology Gram stain separates most bacteria into gram-positive bacteria and gram-negative bacteria. Which of the following stain is NOT used in gram staining? A Methylene blue B Crystal violet C Iodine D Safranin 💡 Explanation Gram stain separates most bacteria into gram-positive bacteria and gram-negative bacteria. Which of the following stain is NOT used in gram staining? ✓ Correct Answer: A. Methylene blue