Pathogenic Cheat Sheet Review

Adan Daramillo's Ultimate Super Powerful Pathogenic Cheat Sheet

  • Phases:

    • Lag Phase: No division; bacteria adapt to environment.

    • Log (Exponential) Phase: Rapid division; significant growth.

    • Stationary Phase: Balanced births and deaths; no net growth.

    • Death Phase: Death rate exceeds reproduction; often due to limited resources.

  • Analogy: 13 Colonies adapting when they arrived—initially not dividing, then adapting to growth, leading to equilibrium.

5.1. Counting Methods

  • Standard Plate Count: Accurate for living cells; reliable between 30-300 colonies.

  • Hemocytometer: Enables counting of living and dead cells, but cannot differentiate between them.

  • Spectrophotometer: Measures turbidity; provides accurate cell counts but includes dead cells.

6. Gram Staining and Differences in Bacteria

  • Gram Staining Process:

    • Uses crystal violet, iodine, and safranin to differentiate bacteria.

    • Gram-Positive Bacteria: Retain crystal violet; thick peptidoglycan cell wall.

    • Gram-Negative Bacteria: Stain pink due to safranin; have a thin cell wall.

  • Endospores and Acid-Fast Bacteria:

    • Endospore Staining: Detects presence of endospores.

    • Acid-Fast Staining: Used for mycolic acid-containing bacteria.

  • Indicators: Blue = mycolic wall, green = does not allow binding.

7. Media Types for Bacterial Culturing

  • Differential Media: Allows distinguishing between different types of bacteria based on their growth characteristics.

  • Selective Media: Only allows specific bacteria to grow while inhibiting others.

  • Example:

    • MacConkey Agar: Detects lactose fermentation; pink colonies indicate positive fermentation.

9. Hemolysis Testing

  • Blood Agar: Used to determine hemolytic property of bacteria.

  • Types of Hemolysis:

    • Alpha Hemolysis: Partial lysis; greenish/brownish color change.

    • Beta Hemolysis: Complete lysis; yellow opaque medium due to consuming red blood cells.

    • Gamma Hemolysis: No lysis; all red agar with streaks.

10. Mannitol Salt Agar

  • Purpose: Medium used to isolate bacteria that can survive in high salt concentration.

  • Interpretations:

    • Yellow indicates Mannitol fermentation (bacteria can survive in salty conditions).

    • Red indicates no growth.

11. Biochemical Testing in Bacteria

  • Focus Areas: Target three macronutrient groups:

    • Carbohydrates: Sugars.

    • Proteins: Amino acids.

    • Lipids: Fats.

12. Glycolysis and Cellular Respiration

  • Glycolysis:

    • Process converting carbohydrates into ATP.

  • Pathway Overview:

    • Plan A: Glycolysis → Krebs Cycle → Electron Transport Chain (ETC) generates most ATP.

13. IMVIC Biochemical Tests

  • Components:

    • Indole Test: Detects presence of tryptophan breakdown. A positive test results in a red ring on top of the medium.

    • Methyl Red Test: Indicates mixed acid fermentation with a red color change.

    • Voges-Proskauer Test: Detects butanediol fermentation by a color change.

    • Citrate Utilization Test: Indicates citrate is the sole carbon source for bacteria.

  • Results Interpretation:

    • Red layer on top = positive for Indole or Mixed Acid Fermenter; negative for Citrate = Blue or Green.