Staining Positively charged dye molecules are attracted to the negatively charged cytoplasm Negatively charged dye molecules are repelled by the negatively charged cytoplasm
Simple Staining Only one color used Crystal violet dye is positively charged, which is attracted by bacteria cytoplasm
Negative Staining A negatively charged dye is used What effect will this have on the bacteria cytoplasm? –The cytoplasm will repel the dye –The background will be stained, but not the bacteria cell –Looks like the night sky
Heat Fixing Cells need to be adhered to the slide using heat –Like an egg frying on a pan As proteins are heated, they denature and stick to the surface We will heat the slides for 2-3 minutes on a hot plate
Gram Staining Gram staining involves a series of staining steps used to differentiate between 2 types of bacteria cells –Gram positive cells – stain blue –Gram negative cells – stain red
Gram Staining Steps 1.Add crystal violet dye (wait 1 minute) 2.Wash slide with water 3.Add Gram’s iodine to lock in stain (wait 1 minute) 4.Add alcohol decolorizer to remove stain from Gram negative cells 5.Add safranin dye (wait 1 minute) 6.Wash slide with water
Warm-Up 1.What is the purpose of staining cells? 2.How do stains work? 3.What is the purpose of Gram staining? 4.What 2 dyes are used in Gram staining? 5.What are the steps of Gram staining?
Bacterial Cells Ideal age for Gram staining bacteria cells is 24 hours Gram positive bacteria are susceptible to certain antibiotics (like penicillin) Gram negative bacteria are susceptible to other types of antibiotics