Estimate how many microbes are in your environment | Homework Help

Microbiology Lab
Unit 2 Lab

Directions: Complete the following Lab Exercises in the Word document. Keep in mind you must use quotation marks if you include sentences that are word for word from the lab manual, textbook, or animations. You should use in text citations when quoting and when paraphrasing (rewording). Also, always include the reference in APA format with corresponding page numbers when quoting and when paraphrasing. Be sure to review the Plagiarism page in the course so that you can be certain you avoid Plagiarism.

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You should save your document and include the following information in the file name: your name, course info, assignment. Also, please save your document in .doc format. Example: JFarrowMicrobioUnit2Lab.doc

You should submit your Unit 2 Lab by using the Unit 2 Lab Dropbox in the course by the due date indicated in the Course Outline. Be sure to review the Assignment Grading Rubric found on the ‘Assignments Expectations’ page in the ‘Begin Course Here’ folder.

Below you will find the Lab for Unit 2 that will involve hands on work to complete. Be sure to read the Lab carefully before starting.

Growing and Identifying Bacteria/Fungus

1. Disposable aluminum muffin tin (contains 6 compartments)
2. Cooking Pot
3. Stirring Utensil
4. Clear plastic wrap
5. Water
6. Knox© brand gelatin
7. Fat Free Beef Bouillon
8. 6 Swabs/ Q-tips
9. Camera

You will need to make your own homemade agar using the following recipe.

Step 1 – Homemade Agar Recipe:

You will need a disposable aluminum muffin tin that has six compartments. For safety and health reasons this item will need to be thrown away at the end of the experiment. The muffin tin will serve as your Petri dish that is used in traditional lab settings.

The tin, the cooking pot, and the stirring utensil should be clean, washed before beginning to make the agar. Let all materials air dry after washing. (Prevents contamination) You will need to cover your dish with saran wrap, clear plastic wrap. This will prevent unwanted species from entering your dish.

Boil ¾ cup of water. Next, aID 1 envelope of Knox© gelatin and stir. Then you will need to aID 2 beef bouillon cubes and stir regularly to dissolve. Once the bouillon cubes are dissolved, turn off heat. The bouillon cubes give the nutrients that the bacteria need to grow. Pour liquid into your petri container compartments and put in fridge for 1 hour. After 1 hour, remove your container and set in safe place out of reach of children.

If using non fat free bouillon cubes, strain cooled broth through paper towel or coffee filter to remove fat.

Step 2 – Preparing your sample:
You should obtain Q-tips or cotton swabs. This will be your means of collecting samples. You will swab six areas of your house, using a clean swab each time. Good places to swab include: bathroom toilet handle, toothbrush, kitchen cabinet, door knobs, keyboard, phone, table surface, etc.

Swab the item, then apply the affected tip to one agar compartment on your dish. Lightly touch the swab to the agar and draw a line. Repeat this process with each sample using a fresh compartment each sample. Be sure to write down the order of your lines, so you do not confuse your samples.

Step 3 – Incubation:
You should let your samples sit at room temperature for 2-4 days, not in direct sunlight. Keep in mind your samples need to be covered with saran wrap or plastic wrap when you are not viewing them. You will need to identify the colonies after sitting (incubating period).

Step 4 – Identifying the colonies:
You need to identify your bacteria/fungus. You need to include the genus only. You do not need to identify species. You may find the following chart helpful in identification. Helpful hint, fungus grows fuzzy, and bacteria have a smooth appearance. If your bacteria are different from below, you should research on the internet to identify. Use the internet to find websites with pictures, descriptions of color, and characteristics of the bacteria or fungus that have been sampled.

Bacteria Shape and dispersion-rod Appearance
Bacillus cereus Shape and dispersion-rod, singles or in short chains Appearance-large, irregular, creamy white

Serratia marcescens
Shape and dispersion-short rods, singles or in chains
Appearance-circular and reIDish

Staphylococcus epidermidis Shape and dispersion-spheres, small pairs or in groups
Appearance-circular, pale translucent white

Streptococcus lactis
Shape and dispersion-oval, elongated in direction of chain or pairs
Appearance-circular, white to grey

Since you are not completely sterilizing the agar itself you may have colonies of bacteria that grow that come from the agar or from the boiled water. Unless you can autoclave your media, it will be difficult to completely sterilize your media. I do not expect you to autoclave your media.

What To Submit For Grading:

You should write a Lab Report including the following sections, you should complete your Lab Report in this document:

Purpose- In this section, you should explain the purpose of the Lab in general.

Hypothesis- In this section, you should explain what you expect to take place in the Lab.

Procedures- In your Procedures section, you should explain the steps you took during the Lab and what or where you swabbed. You should explain the Procedures in your own words, do not copy the procedures from the directions.

Results- In the Results section, you should make a table and include 3 genus names of the bacteria and fungus you identify in your petri dish. You should describe the appearance of your growth, including color and patterns. You should avoid copying the table presented in the Lab. You should also include a few sentences of background information and characteristics of your bacteria and fungus in your own words. ***If you do not grow 3 genus of bacteria or fungus, you may include information concerning bacteria or fungus you could have found in your samples. Be sure that you are clear concerning if you grew the organisms. Provide exact references used when completing this lab in APA format.

In aIDition, using a digital camera, you should include a photo of your Lab set up and a photo of your petri dish showing your growth on the last day of growth. These photos should be INSERTED into the word document. Please size your pictures small so that upload time and download time is reduced. I will be able to enlarge the pictures when grading.

Another option is to upload your pictures to then include the web aIDress to view your pictures in your document.

Conclusions- In the Conclusions section, write about your experience completing this lab. Discuss what you learned and how the knowledge can apply to daily life. In aIDition, please include your responses to the following questions in sentence format within your conclusions.

You should read the Lab manual and review the Growing Microorganisms PowerPoint presentation that is included in this Unit. You should respond to each of the following questions. Each answer should not exceed 100 words each in length.

1. Explain how you can estimate how many microbes are in your environment that you sampled.
2. Explain two conditions of incubation that affect microbial growth.
3. Count the colonies in your samples. Also, explain each of these microbiological terms and abbreviations: countable, NG, TFTC, TNTC.
4. Explain your experiences using the streak plate method.


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