2420-Lab 7- Microbial Growth: Temperature, Oxygen and Osmotic Balance

Directions:

Answer following questions after reading the information and watching the video from the link below. Use color RED or BLUE for your answers. Submit the completed document on eCampus for grading. Refer to

• the textbook chapter 4 (sections 4.1, 4.3 and 4.4) (Nester- McGraw Hill)
• Lab Manual by Dr. Su, pages (optional)
• Link: Environmental Influences of Bacterial Growth, Virtual Edge Experiment-5A-B
• pH Requirement of bacteria

Bacterial Growth:

Read the information from textbook from chapter 4 review sections 4.1, 4.3 and 4.4 to answer the following questions.
Watch the following video:

• For background: Bacterial Growth

1. Label the phases of growth on the following curve:
2. What happens to bacteria in the phases labeled as A, B, C and D in the above figure?

A:
B:
C:
D:

3. If we add more nutrients and space at the end of the exponential phase for a growing bacterial culture, what will happen?

Oxygen Requirement of bacteria

Read the information from textbook from chapter 4 review sections 4.3-4.4 to answer the following questions.
Watch the following videos:

• For background: Oxygen Requirement of bacteria
• For experiment: Oxygen requirement of bacteria using soft agar

Results of the bacterial oxygen requirement of bacteria:

4. Why can only some organisms tolerate oxygen?

 

5. Describe the kind of bacteria shown in the figure above in terms of oxygen (concentration) requirement and special enzymes.

 

6. Which oxygen related enzymes are present or absent in the bacteria from tubes A-E?

 

Temperature Requirements of Bacteria:

Read the information from textbook from chapter 4 review sections 4.3-4.4 to answer the following questions.
Watch the following videos:

• For background: Temperature Requirement of bacteria
• For experiment: Temperature Influence on bacterial growth

Temperature tolerance of bacteria

Write the correct term for bacteria growing under the following conditions

7. Most medically important bacteria
8. Bacteria growing on or inside your body
9. Bacteria growing in your refrigerator
10. Bacteria growing in the arctic ocean in winter
11. Bacteria growing in hot springs in Arkansas
12. Bacteria growing in geysers
13. Why are bacteria not able to grow at temperature higher than the maximum tolerance limit?
14. Do bacteria grow at the temperatures lower than the minimum tolerance limit? Why or why not? Explain

Osmotic Balance Requirements of Bacteria:

Read the information from textbook from chapter 4 review sections 4.3-4.4 to answer the following questions.
Read the following:

• For experiment: Osmotic Influences

Osmotic tolerance of bacteria

Halophiles: On human body, Staphylococcus aureus is known to tolerate sweat. These bacteria may cause skin infections if athletic gear is shared among athletes without proper sanitization. In nature we will find bacteria, algae and fungi in water bodies or soil with higher salt concentrations. These organisms come under a group called “halophiles”.
Habitat: Halophiles are usually found in salt lakes, salt marshes, subterranean salt deposits, dry soil, salted meat and hypersaline seas.
3 groups based on the salt concentration tolerance:

• Halophiles-2-5% salt required for growth
• Moderate halophiles-5-20% salt required for growth
• Extreme halophiles-20-30% salt required for growth

Write the correct term for bacteria growing under the following conditions

15. Based in your knowledge about tonicity, for cells to survive they have to be surrounded by ______tonic environment.

 

16. Why would cells not survive in hypotonic or hypertonic environment?