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

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

• the textbook Openstax Microbiology- Chapter 9

• Link: Environmental Influences of Bacterial Growth, Virtual Edge Experiment-5A-B

• pH Requirement of bacteria

• This document has 16 questions to answer.

• Students MUST use scientific terminology while answering all questions

• For each wrong answer 0.5 points will be deducted

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:

1. What happens to bacteria in the phases labeled as A, B, C and D in the above figure?

A:

B:

C:

D:

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

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

1. Why can only some organisms tolerate oxygen?

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

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

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

Write the correct term for bacteria growing under the following conditions based on temperature requirement:

1. Most medically important bacteria

2. Bacteria growing on or inside your body

3. Bacteria growing in your refrigerator

4. Bacteria growing in the arctic ocean in winter

5. Bacteria growing in hot springs in Arkansas

6. Bacteria growing in geysers

7. Why are bacteria not able to grow at temperature higher than the maximum tolerance limit?

8. Do bacteria grow at the temperatures lower than the minimum tolerance limit? Why or why not? Explain

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

Halophiles vs. Halotolerant bacteria:

Some bacteria can tolerate but do not require high salt concentrations to grow and these are called halotolerant bacteria.

Some bacteria can tolerate and require high salt concentrations to grow and these are called halophiles. There are 3 groups of halophiles as based on the requirement of salt concentration for growth.

3 groups based on the salt concentration tolerance:

• Halophiles (or slight halophiles)-2-5% salt required for growth

• Moderate halophiles-5-20% salt required for growth

• Extreme halophiles-20-30% salt required for growth

Habitat: Halophiles are usually found in salt lakes, salt marshes, subterranean salt deposits, dry soil, salted meat and hypersaline seas.

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 “halotolerant”.

Write the correct term for bacteria growing under the following conditions

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

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