Name: Jenny Mae R. Cadiveda Section: 1BSN6 Streak Plate Activity Report Observations and Results 1. Define the term “colony” as it relates to bacterial growth on solid media. - A colony is a visible mass of bacteria that has grown on solid media. It is formed when a single bacterial cell divides and multiplies, forming a cluster of cells. Colonies are typically circular or irregular in shape and can range in size from a few millimeters to several centimeters. 2. Examine your isolation streak plate. (Attach a photo of your streak plate – original image) Did you obtain single, isolated colony? (Upload another photo, draw circle over your single, isolated colony). Original Image - Yes, I obtained single, isolated colony. Another photo where I circled the isolated colony 3. How can you determine if the colony that you chose to isolate is a pure culture? - The best way to determine if the colony that you chose to isolate is a pure culture is to perform a streak plate test. This involves taking a sample of the colony and streaking it onto an agar plate. If the resulting colonies on the plate are all identical, then it is likely that the original colony was a pure culture. 4. Does each discrete colony represent the growth of one cell? Explain your answer. Why can a single colony on a plate be used to start a pure culture? - No, each discrete colony does not represent the growth of one cell. A single colony on a plate is made up of many cells that have all descended from a single parent cell. This is known as clonal growth. A single colony on a plate can be used to start a pure culture because it contains only one type of organism, which has been isolated from other organisms in the environment. 5. What colony characteristics can be used for differentiation of bacterial species? - Colony characteristics that can be used for differentiation of bacterial species include size, shape, color, texture, elevation, and margin. Additionally, the presence or absence of pigmentation and the presence or absence of a halo can also be used to differentiate bacterial species. 6. In the streak-plate technique, how are microorganisms diluted and spread out to form individual colonies? - In the streak-plate technique, microorganisms are diluted by transferring a small amount of the sample to a sterile agar plate. The sample is then spread out over the surface of the agar plate using a sterile loop or spreader. This process is repeated several times, with each successive transfer diluting the sample further and spreading it out over a larger area. After several transfers, individual colonies of microorganisms will form on the agar plate. 7. Which area of a streak plate will contain the greatest amount of growth? The least amount of growth? Explain your answers. - The area of a streak plate that will contain the greatest amount of growth is the area where the bacteria was first streaked. This is because this area contains the highest concentration of bacteria, as it has not been diluted by subsequent streaking. The area of a streak plate that will contain the least amount of growth is the last area that was streaked. This is because this area contains the lowest concentration of bacteria, as it has been diluted by all previous streaking. 8. How can a streak plate become contaminated? - A streak plate can become contaminated if it is exposed to airborne bacteria, if it is handled with unclean hands, or if it is stored in an unclean environment.
