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Lab 4: MAKING AGAR PLATES You will download this document (“File” → “Download as”) and then save it on your computer

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Lab 4: MAKING AGAR PLATES

You will download this document (“File” → “Download as”) and then save it on your computer. Working on your own, answer the questions below, beneath each question, typing your answer in a different font and/or color from what I have used for this document. After you have completed your assignment, make sure your document is saved as a Microsoft Word document or a PDF with the file extensions .doc, .docx, or .pdf and then submit it through the indicated link in Canvas.

 

Always answer in your own words. If you must use an outside source (which you will for a few of the questions) make sure it is scholarly. No credit will be given for answers without a scholarly source. If you are copying something word-for-word, remember to use quotation marks.

 

Making Agar Plates

Did you know that every surface in your home is teeming with microorganisms? Culturing microbes from your home on petri dishes lets you grow some of them as colonies that you can see with your naked eye. You might already have what you need in your kitchen cupboard.  If not, the ingredients are readily available at most grocery stores. You will be practicing your petri dish making in this lab, since you will be using this technique throughout the semester.
 

To make petri plates, you’ll need disposable containers (see below), beef bouillon cubes or granules, plain gelatin or agar agar*, water, sugar and Q-tips. (*Agar-agar can be found with Asian groceries in some grocery stores.) **Gelatin will melt if it gets too warm, and some strains of bacteria can liquefy it, which is why scientists in labs use agar to make their plates.  The idea to use agar for plates originally came from Angelina Hess, who used agar for canning food.

For containers, you can use foil muffin tins, clear plastic cups covered with plastic baggies, clear Tupperware with lids, or real petri dishes.  This example uses clear deli containers. Containers must be heat-resistant enough to pour warm agar into.

Mix together:

• 1 cup water 
• 1 Tbs. agar-agar (OR one and one half packages gelatin, which is about one and a half oz. or 12g)
• 1 bouillon cube (or 1 tsp. granules)
• 2 tsp. sugar

 

Bring the mixture to a boil on the stove or in the microwave, stirring at one minute intervals and watching carefully until the gelatin or agar is dissolved.  Remove the boiling liquid from heat and cover.  Let cool for about fifteen minutes.

Pour the medium carefully into clean containers, until 1/3 to 1/2 full.  Loosely place lids, foil or plastic baggies over containers and allow dishes to cool completely.  The gelatin or agar should make the growth media hard like jells.  When your plates have hardened, store them in a cool place, like a refrigerator, before using.  Plates should be used in 2-3 days.  When you are working with the plates, try to keep the lids on loosely whenever possible, so that they are not contaminated by microorganisms floating around in the air.  If you’re planning to use muffin tins, simply place them in a muffin pan, fill them with agar, and when they’re cool, put them in individual zip-lock baggies.  With other containers, put the lids on tightly once the plates harden.

 

Questions

1. Describe how you will improve your plate making technique? (5 pts)
2. Include an image of you with your plates here (10 pts)