Calculate the CFU/mL.

Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
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**Calculate the CFU/mL**

The diagram illustrates the process of performing serial dilutions to calculate Colony Forming Units per milliliter (CFU/mL) from a bacterial specimen. 

1. **Initial Dilution:**
   - Start with 1 mL of the bacterial specimen.
   - Add this 1 mL to a tube containing 9 mL of diluent (e.g., saline or broth), resulting in a total volume of 10 mL. This is a 1:10 dilution.

2. **Serial Dilutions:**
   - Take 1 mL from the first dilution and transfer it to a second tube with 9 mL of diluent, achieving a 1:100 dilution (second tube).
   - Repeat this process twice more:
     - Third tube: 1:1,000 dilution.
     - Fourth tube: 1:10,000 dilution.

3. **Plating:**
   - From each diluted tube, take 0.1 mL and spread it onto an agar plate. 
   - This step is repeated for all four dilutions to facilitate counting colonies after incubation.

**Explanation for Educational Use:**
- Each subsequent dilution reduces the concentration of bacteria, making it easier to count distinct colonies after incubation.
- The dilution factor increases tenfold at each step.
- The process allows for estimation of the original concentration of bacteria in the specimen by counting colonies and back-calculating using the dilution factors.
Transcribed Image Text:**Calculate the CFU/mL** The diagram illustrates the process of performing serial dilutions to calculate Colony Forming Units per milliliter (CFU/mL) from a bacterial specimen. 1. **Initial Dilution:** - Start with 1 mL of the bacterial specimen. - Add this 1 mL to a tube containing 9 mL of diluent (e.g., saline or broth), resulting in a total volume of 10 mL. This is a 1:10 dilution. 2. **Serial Dilutions:** - Take 1 mL from the first dilution and transfer it to a second tube with 9 mL of diluent, achieving a 1:100 dilution (second tube). - Repeat this process twice more: - Third tube: 1:1,000 dilution. - Fourth tube: 1:10,000 dilution. 3. **Plating:** - From each diluted tube, take 0.1 mL and spread it onto an agar plate. - This step is repeated for all four dilutions to facilitate counting colonies after incubation. **Explanation for Educational Use:** - Each subsequent dilution reduces the concentration of bacteria, making it easier to count distinct colonies after incubation. - The dilution factor increases tenfold at each step. - The process allows for estimation of the original concentration of bacteria in the specimen by counting colonies and back-calculating using the dilution factors.
The image depicts a series of petri dishes, each shown in two stages: before and after bacterial growth. The progression from left to right illustrates a dilution series used to quantify bacterial colonies.

- **Stage 1:** The first petri dish shows a dense concentration of bacterial colonies. Below it, the petri dish contains approximately 800 colonies.
  
- **Stage 2:** The second petri dish shows a slightly reduced density of colonies. Below it, the petri dish contains approximately 550 colonies.

- **Stage 3:** The third petri dish has fewer colonies compared to previous stages, with a less concentrated distribution. Below it, the petri dish contains about 122 colonies.

- **Stage 4:** The fourth petri dish further reduces in the number of colonies, showing scattered distribution. Below it, the petri dish contains approximately 20 colonies.

- **Stage 5:** The final petri dish shows a minimal presence of colonies, almost clear of bacterial growth. Below it, the petri dish contains about 3 colonies.

This sequence illustrates the process of serial dilution, used to obtain countable colony numbers for accurate bacterial quantification.
Transcribed Image Text:The image depicts a series of petri dishes, each shown in two stages: before and after bacterial growth. The progression from left to right illustrates a dilution series used to quantify bacterial colonies. - **Stage 1:** The first petri dish shows a dense concentration of bacterial colonies. Below it, the petri dish contains approximately 800 colonies. - **Stage 2:** The second petri dish shows a slightly reduced density of colonies. Below it, the petri dish contains approximately 550 colonies. - **Stage 3:** The third petri dish has fewer colonies compared to previous stages, with a less concentrated distribution. Below it, the petri dish contains about 122 colonies. - **Stage 4:** The fourth petri dish further reduces in the number of colonies, showing scattered distribution. Below it, the petri dish contains approximately 20 colonies. - **Stage 5:** The final petri dish shows a minimal presence of colonies, almost clear of bacterial growth. Below it, the petri dish contains about 3 colonies. This sequence illustrates the process of serial dilution, used to obtain countable colony numbers for accurate bacterial quantification.
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