1. The World of Bacteria

2. What does a bacterium look like?
Internal Structures:
cytoplasm
nucleoid
ribosomes
Boundaries:
cell membrane
cell wall
capsule
Appendages:
flagellum
pili

3. Shapes of Bacteria

4. Bacteria Identification Criteria
Shapes
Bacilli
Cocci
Sprilli
Growth Patterns
“Prefixes describe pattern”
“strepto…. Means in chains
“staphylo…Means in clusters
Examples:
Streptococcus pneumoniae

5. Bacterial Growth Patterns: Streptococcus

6. Bacterial Growth Patterns: Staphylococcus

7. The Gram Stain Christian Gram (1884) develops gram staining process.
Use of two stains: crystal violet and safranine
Stains interact differently with a particular type of cell wall.
Cells will be either Gram positive or Gram negative.

8. How else are bacteria identified? Another criterion?
Composition and Construction of the Cell Wall

9. Gram Negative
The Gram-negative cell wall is composed of a thin, inner layer of peptidoglycan and an outer membrane consisting of molecules of phospholipids, lipopolysaccharides (LPS), lipoproteins and sutface proteins. The lipopolysaccharide consists of lipid A and O polysaccharide.

10. Gram Staining Process
Place bacteria on slide.
Fixation is prep cells.
Fixation means to prep cells for staining Flood slide with crystal violet stain. Add the idodine. Decolorization means to wash away any crystal violet that was not picked up by the cell walls with alcohol. Last, flood slide with safranin. If cell did not pick up the crystal violet, it means cell wall is different and safranin will stainl
What color are gram positive? What color are gram negative?

11. Which is Gram positive? Which is Gram negative?
Gram negative:  A group of bacteria that do not retain the crystal violet dye after the differential staining procedure known as Gram staining.  They appear pink due to the counterstain, safranin.  Gram positive appears purple. The difference between Gram negative and Gram positive bacteria is the cell wall structure, which accounts for the different staining characteristics

12. The Gram Stain Results:
Gram Positive
Gram Negative
So what is the medical significance of this technique?

13. How Bacteria Talk by Bonnie Blasser