Gram stain

• Usually first test done to identify bacteria
• Gram positive bacteria have walls containing large amounts of peptidoglycan (a starch)
• Gram negative bacteria are harder to control with antibiotics due to having a thick peptidogylcan layer
• Gram stain practical:

  • Stain crystal violet
  • Stain with gram iodine
  • Wash with alcohol
  • Stain with saffernin
• Thick:

  grams and crystal stuck so doesn't wash out. (Can't see light seffarnin)
• Thin:

  Crystal and gram wash out so can't see seffarnin