Quadrant streak plate method_2024sp(1)

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Rowan-Cabarrus Community College *

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MICROBIOLO

Subject

Biology

Date

Apr 3, 2024

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docx

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2

Uploaded by ProfBoulderNightingale32

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Isolating bacteria: quadrant streak plate method lab Part 1: Terminology and procedure questions from videos 1. Read over the information in the practical 1 folder in Bb, especially the online lab manual ( LINK ). 2. Watch the videos and go over the websites posted in this folder. You will be answering questions on this video, so please go over the questions first. There is a powerpoint posted that also has helpful information on this procedure. 3. Complete the following questions: a. What do we mean by a mixed culture? One that contains two or more known species. b. What is a colony? Group of bacterium grown on agar medium c. A colony forming unit is a unit of bacteria that grows into distinct colonies on an agar plate. Go over the arrangement of bacterial cells again (streptococci, tetrad, etc). Do you believe all colonies start with just one single bacterial cell? Explain your answer. Yes I believe that due to colonies have parental bacteria that is capable of replicating. d. Briefly explain how this method helps one to isolate individual colonies? Why do we use four quadrants? What are we doing as we move from one to the next? It is important because it allows us to examine different characteristics that you may be looking for within the same bacterium. By dividing the plate into four quadrants, the sample is thoroughly diluted. Each time further diluting the sample. e. To perform this procedure, you need to start with an original sample or culture. This can be a liquid culture or a culture grown on agar. During this procedure, how many times do you use the original culture? Why? The original culture is used only once to get the initial parental bacterium for replication and streaking. Part 2: Practicing the isolation streak method 1. Complete the virtual lab . This link will take you to virtual laboratory page. Select “Streak Plate”. Read the background information, and then click to open the learning module. You can read the description and steps, and then select Start. 2. Using the virtual lab, practice the isolation streak until you get isolated colonies. Take a screen shot, or use the snipping tool, to take a picture of your results. Save it to your computer so that you can upload it below. If you are having trouble with the virtual lab, make sure to pick up the inoculating loop first and hold it over the Bunsen burner. You have to do this for each streak. 3. Answer the following questions:
a. How many times did you have to practice before you were able to obtain isolated colonies? If more than once, do you have an idea of why you were unsuccessful in the prior attempts? (Don’t be afraid to say it took more than once; it takes practice!) It took me two times because I was struggling with what I was supposed to do after I sterilized the loop once I was done with the first quadrant. b. In which quadrant did you first see isolated colonies? The third quadrant. c. Post an image of your results here: d. What do you believe would happen if you did not flame your loop in between each quadrant on the streak plate? You wouldn’t see individual colonies and bacteria would be spread all throughout the plate.
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