lab 4 acid fast and endospore staining

• Acid-Fast staining differentiates two types of cells:

  • have waxy mycolic acid in cell wall
  • don't have mycolic acid in cell wall
• There are two methods for acid-fast staining:

  • the Ziehl Neelsen
  • the Kinyoun
• fundamental difference is that Ziehl-Neelsen uses heat and Kinyoun doesn't use heat
• in lab, Kinyoun method will be used
• primary stain = carbolfuchsin

  counterstain = methylene blue
• acid-fast positive bacteria have mycolic acid in their cell walls and are stained red
• acid-fast negative cells will be decolorized by acid alcohol and appear blue from the counterstain
• several specific diseases are caused by acid-fast bacteria such as tuberculosis and leprosy
• when environmental conditions become unfavorable, some bacterial species can develop endospores
• what are unfavorable conditions?

  • low nutrients
  • low humidity
  • high temperature
• endospores are a metabolically inactive state of the cell that possess a tough outer keratin layer
• endospores are highly resistant to heat and chemicals and allow bacteria to survive for long periods of time in harsh environmental conditions
• when conditions become favorable again, endospores undergo germination to return to metabolically active state
• metabolically active cells are referred to as vegetative cells
• The Schaeffer-Fulton method is the most common method to stain endospores. This method uses steam to push the primary stain into the endospores
• primary stain= malachite green

  counterstain = safranin