The Biology Spot:

The Microbiology Classroom

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Unit 1: Fundamentals of Microbiology (Ch 1 &3)

 

Follow-up to Lab 1: The Ubiquity of Microbes

Background Questions

1) Compare and contrast agar versus broth media.

 

 

 

 

2) What are three ways you can discern the type of microbe growing on your agar plate?

 

 

 

3) Explain who is responsible for the recipe of the agar used today in microbiology labs.

 

 

 

4) Describe how Robert Koch came up with the germ theory of disease still used today. ( use intro in lab and page 411 of book)

 

 

 

 

 

 

Part I: Microbe Hunt

A) Initial Questions:

1) Why is it necessary to use a disinfectant out of a squirt bottle vs. spray bottle?

 

 

 

2) Why should you never leave the lid of the petri-dish on your desk? Why should you always open your plate like a clamshell?

 

 

3) Why were you told to first moisten the swabs with water before swabbing the sample tested?

 

4) Why must you seal your plate after you have taken your sample?

 

5) Why are your plates incubated in inverted position (jelly side up)?

Making Plate Observations and Counts:

1) Use the table on the following page to determine shape, margin, and elevation.

2) Record your count of colonies using the following scale.

0

No bacterial growth

+

1-10 colonies

++

11-50 colonies

+++

51-100 colonies

TNTC (too numerous to count)

More than 100 colonies

Part B: Results:

Sketch

Description

Part A: Air sample

Your location: __________

 

 

 

 

 

 

 

 

Shape:

Margin:

Elevation::

Color:

Abundance and consistency of colonies:

Reason for growth or no growth:

Other:

Part B: Finger and toe samples

Shape:

Margin:

Elevation::

Color:

Abundance and consistency of colonies:

Reason for growth or no growth:

Other:

Part C Other Body Sample

Location: ________________

Shape:

Margin:

Elevation::

Color:

Abundance and consistency of colonies:

Reason for growth or no growth:

Other:

Part D: Money Sample

Type: ______________

Shape:

Margin:

Elevation::

Color:

Abundance and consistency of colonies:

Reason for growth or no growth:

Other:

Part C: Follow-up Questions

1) List the locations of various air samples tested in our class. Which sample had the greatest numbers of colonies? Why do you think this sample had such a high microbial count?

 

 

 

 

 

 

 

 

 

 

 

2) Would you prefer to shake a person's hand or foot after this experiment? Explain why or why not.

 

 

 

 

 

3) Why is 37 C a desirable incubation temperature for most cultures of microbes?

 

 

 

 

 

4) Describe some of the differences in the macroscopic appearance of bacterial and fungal colonies.

 

 

 

 

 

5) What are some ways we can keep our money more germ free?

 

 

Part II. Preparation of Nutrient Agar

Follow-up questions

1) List 6 ingredients you think might be found in nutrient agar.

 

 

 

 

 

2) What is an autoclave? What objects should be autoclaved in the microbiology lab?

 

 

 

 

 

3) Why must agars be autoclaved before being poured?

 

 

Part III. Winogradsky column: A Soil-Based Microbial City

 

Part A: Initial Questions

1) Describe the ingredients you put into your Winogradsky column. Explain why you put each in your bottle.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2) Describe what type of bacteria might grow at the top , middle and bottom of your column and why,

 

 

 

 

 

 

3) Where do you think most bacteria will be found in your column? Explain why.

 

 

 

Part C: Results: Mark your bottle at the various depths. Comment on appearance (color, etc.) each week. Make sure to maintain 1 cm water level at the top at all times.

Depth level

(cm)

Week 1 Observations

Date: _______

Week 2

Observations

Date: _______

Week 3

Observations

Date: _______

Week 4

Observations

Date: _______

Week 5

Observations

Date: _______

Week 6

Observations

Date: _______

20

 

 

 

 

 

 

 

 

 

18

 

 

 

 

 

 

 

 

16

 

 

 

 

 

 

 

 

 

 

 

14

 

 

 

 

 

 

 

 

12

 

 

 

 

 

 

 

 

10

 

 

 

 

 

 

 

 

8

 

 

 

 

 

 

 

 

6

 

 

 

 

 

 

 

 

4

 

 

 

 

 

 

 

 

2

 

 

 

 

 

 

 

Part IV. Microbial Yogurt

 

Part A: Results: Comment on the appearance, smell and taste of the yogurt cans.

Observations

Week 1

Week 2

 

Can 1: Experimental can inoculated

with live culture

 

Can 2:Control can

with no live culture

Part B: Follow-up Questions

 

1) Two of the most common bacteria found in yogurt are Lactobacillus bulgaricus and Lactococcus thermophilus. These bacteria are said to be anaerobic and thermophilic. Explain what these two terms mean ( anaerobic and thermophilic).

 

 

 

 

 

2) Describe in detail why yogurt has a sour taste to it.

 

 

 

 

3) Why is there an expiration date on yogurt and most dairy products?

 

 

 

 

 

4) What is the purpose of the control can and the experimental can in this experiment?

 

 

Overall Question of the Entire Lab: Are microbes ubiquitous? Explain why or why not in an organized paragraph.

 

Questions or Comments can be sent by e-mail to Moore Biology