lab 5 Micro

Steps for gram staining process/effect

1) Primary Stain: Crystal violet added. Stains cells purple/blue

2) Mordant Stain: Iodine added- binds with crystal violet to form insoluble complex so stain stays put (remains purple/blue)

3) Decolorizer: Alcohol added. Decolorizer washes away stain from gram-negative cell wall (gram negative cells are now colorless)

4) Counter stain: Safranin added- counterstain allows dye adherence to gram negative cells (gram positive still purple, gram negative now pink/red)

Preceding steps (before staining)

1. Prepare a smear by placing sample on slide

2. Heat fix the slide to ensure the bacteria stick to the glass

Contamination vs Pure culture

multiple colonies vs single

1) Simple Stain

2) Differential Stain

1) Dye added to distinguish cells from background

2) Dye added to distinguish different cell parts