Bacterial Morphology and Staining Techniques

  1. Coccus (cocci, plural)
    a spherical or round-shaped bacterium with a diameter of about 0.5 μm
  2. Bacillus (bacilli, plural)
    a cylindrical or rod-shaped bacterium about 0.5 μm to 20 μm in length
  3. Spirilla (spirillum, plural)
    a helical or spiral-shaped bacterium about 15 μm in length
  4. Image Upload 1
    Coccus (spherical, round-shaped bacterium of about 0.5 μm
  5. Image Upload 2
    Bacillus (cylindrical or rod-shaped bacterium, about 0.5 μm to 20 μm in length
  6. Image Upload 3
    helical or spiral-shaped bacterium, about 15 μm in length
  7. Which of the 3 bacterial arrangements DO form organized arrangements?
    cocci and bacilli
  8. What is unique about spirillum?
    Remain as single cells and do not form clusters or chains.
  9. Which out of the 3 has the greatest variation in their arrangements?
  10. Cocci being able to form the most number of arrangements. Name the order of arrangements. What's significant about this bacterium?
    • First - coccus (cocci) 
    • Separates and then "pair" of coccus known as diplococci.
    • Separates and becomes a group of 4, called tetrads.
    • Then so on and so forth to 8, 16, and ever greater number of cells, called sarcina. Once they read, hundred of continuous, bread-like chains and into grape-like clustes and irregular clumps called straphylocci.
  11. Bacilli have fewer arrangements but can pair together end-to end forming:
  12. Bacilli cells which become linked together as diplobacilli and formed chains of cells are called:
  13. What are bacilli cells that line up side-by-side at angles in an arrangement, or in a stack?
  14. Define Simple stain -
    One dye is used to directly stain the bacterial cell or the background. Cell shape, size, and arrangement may be determined with simple staining techniques.
  15. Define Direct stain -
    A type of simple stain; only the bacterial cell becomes colored, leaving the background or external environment clear and colorless.
  16. Define Negative stain -
    A type of simple stain; the cell is unstained and appears as a bright, often colorless object against a dark-stained environment.
  17. Differential stain -
    Two or more dyes are used. Cell morphology can be described and identification of the structural components (composition of the cell wall and other cell features like flagella, capsules, or endospores) is possible.
  18. What kind of charge does a basic stain chromosome contain?
    (+) charge. This makes it possible for a cells membrane (which is slightly negative) to attracted to the dye.
  19. What type of stains are done using basic dyes(+)? Why?
    Direct stains. Because this type of staining techniques only colors the cytoplasm and leave the background outside of the bacterial cell colorless.
  20. Name 5 basic dyes:
    • Crystal Violet
    • Methylene Blue
    • Safranin
    • Basic Fuchsin
    • Malachite Green
  21. What's the charge of an acidic stain chromosome?
  22. What stains repel the cells negative charge? What does this show?
    Negative, Acidic (-) stains. Negative stains color only the background or environment outside of the cell.
  23. What 3 colors are used in an acidic/negative stain?
    • Congo Red
    • India Ink
    • Nigrosin
  24. How are cells preserved on a slide? What is this process called?
    A flame is used to kill the bacteria and firmly affix the cells to the slide, fixation process.
  25. What happens if you overhead during the fixation process?
    The bacteria may deteriorate, remove it from the surface.
  26. How are the two types of dyes distinguished?
    By either gram negative(acidic), or gram positive (basic)
  27. Which bacteria, gram-negative or gram-positive, has a thigh outer cell wall?
    Gram Positive
  28. How is a cell described if it remains crystal violet throughout the gram stain procedure? gram-negative or positive?
    Gram Positive.
  29. Why doesn't the color changed when staining a gram-positive bacterium?
    Because the cells walls are thick and extensively cross linked, allowing the dye complex to stay bound and fixed in the decolorization process.
  30. How do gram-variable stains appear?
    May appear as both types of cells when stained, either gram-positive or gram-negative.
Card Set
Bacterial Morphology and Staining Techniques
Week 3 Lab QLC 350