Lab 2

Lab 2

1. Gram Stain

   • Crystal violet - taken up by gram positive bacteria
   • Gram's Iodine
   • Acetone/Alcohol Mix - removes crystal violet in gram negative bacteria
   • Safranin - taken up be decolourised gram negative bacteria

2. Yeasts and Fungi

   • Yeasts (unicellular)
   • Moulds (multicellular)
   • Fungal spores proliferate in warm, moist conditions
   • Stained with lactophenol blue or light green
   • Candidas albicans (spherical cells --> budding into long thin extension of the cell known as pseudohyphae)
   • Moulds have multicellular hyphae (main mode of vegetative growth)
   • Moulds form conidiophores (fruiting bodies) for reproduction which contain conidia (spores)

3. Ziehl- Neelsen Acid Fast Stain

   • Mycobacteria do not stain by Gram stain
   • Facilitated by the application of heat
   • Once stained, they retain dyes and resist decolorisation with acid or alcohol
   • Therefore are called acid fast organisms
   • Acid-fast organisms retain the red carbon fuchsin primary stain (appearing red)
   • Non-acid fast organisms are decolorised. They accept the counterstain methylene blue and appear blue.