Lab-3-Culturing and Aseptic Technique (1)

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American Public University *

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MICROBIOLO

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Chemistry

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Dec 6, 2023

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Lab 3: Culturing and Aseptic Technique (100 points ( -Each question on the lab worksheet must be answered completely, thoroughly, in complete sentences and correctly in order to be considered for full credit -If the question asks you to do research or find a source, a reputable, credible and/or scholarly source cita- tion must be included in order to be considered for full credit -If a math formula is required to arrive to an answer, work must be shown otherwise, no credit will be awarded Pre-Lab Questions 1. Proper aseptic technique is crucial to ensuring the growth of pure bacterial colonies. What is the experimental way you can test your practices to confirm that you are using the proper aseptic technique? (5 points) A way that you could test if you’re practicing the correct aseptic technique would be having a control petri dish and seeing if there is any growth after a couple of days. If there is growth, then you did not practice proper aseptic technique and if there is not, then you did it properly . 2. In a laboratory setting, what are three ways you can properly sterilize culturing equipment? (5 points) The three ways are wet heat(autoclave), dry heat(flame), or UV radiation . 3. For each inoculation tool, give one scenario in which use of that tool would be appropriate. (5 points) Inoculation loops are used to collect inoculum from cultures. Loops can be useful when transferring microbes from one plate to another . Sterile cotton swabs are often used to collect microbial samples directly from a variety go surfaces. This is often the tool used when beginning a culture plate in a microbiology lab . Inoculation needles are used to collect microbes from a defined region of a culture and transfer to another medium or container. It can also semisolid media or stab tubes . Culturing and Aseptic Technique

Culturing and Aseptic Technique

Experiment 1 Results Tables Table 1: Experiment 1 Colony Growth (15 points ( Plate Number Source Growth (color, amount, shape, etc.) 1 Mouth Light yellow, two small dots on the side of the peri dish 2 Floor Grey, light brown , brown, orange. Round dots scattered all over the 3 Table surface Cream to yellow. One yellow dot with crystal partten, the milky dots are small 4 Negative control No growth found 5 Airborne Control One small milky dot Culturing and Aseptic Technique

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Experiment 1 Post-Lab Questions 1. Do some research and try to identify one to three types of microbes cultured on your plates. Using any resources available to you (i.e., a textbook or internet sources such as the CDC website), look up what bacteria are usually found on the areas from which you obtained your samples and the morphological characteristics of their colonies. Describe what morphological traits (i.e., size, shape, arrangement, color, margin, etc.) led to your hypothesized species identification. Be as specific as possible in the microbe type. (5 points) Staphylococcus: Gram-positive cocci about 0.5 – 1.0 μm in diameter Staphylococcus aureus : that are Gram-positive and appears in a spherical shape. They are often in clusters resembling bunches of grapes when observed under a light microscope after Gram staining . Bacillus - rod shape, gram-positive , aerobic sice- 1.5 um, arrangements- chain-like structure, color- fuzzy white and slightly yellow 2. For the colonies hypothesized in Question 1, specify which plate and source the microbes came from. Are you surprised to find this type of microbe on this surface? (5 points) I have detected some Staphylococcus from my child's mouth. I’m not surprised to find that bacteria in his mouth, this is a very common bacteria in humans. One study found that 94 percent of healthy adults carried some form of Staphylococcus bacteria in their mouth and 24 percent carried S. aureus 3. Looking at your negative control, did you perform a proper aseptic technique or were your plates contaminated? If contamination did occur, list the possible sources and how you can prevent contamination in the future. (5 points) My negative control was not contaminated, so I believe I did perform a proper aseptic technique . 4. Was there a large risk for airborne contamination of your experimental plates (look at your airborne control plate)? Based on the colonies that grew on your plates, do you think any of your experiment plates received airborne contamination? (5 points) There is only one small milky dot that appears in my petri dish. I don’t think there was a large risk of airborne contamination in the room where I collected samples of my experiment plates . I do think some of my experiment plates received airborne contamination because I do see the same small mill dots appear on other plates . Culturing and Aseptic Technique

Culturing and Aseptic Technique

Experiment 2 Results Tables Table 2: Initial Reserved Plate Colony Growth Observations (15 points ( . Plate Sample Appearance (morphology, etc (. 1 Yellowish-white streak, single cluster spread out on plate 2 Yellowish-white streak, single cluster spread out on plate 3 Yellowish-white streak, single cluster spread out on plate Table 3: Final Plate and Stab Tube Growth Observations (15 points ( Sample Form Growth? (Yes or No ( Same Appearance as Initial Plate? (Yes or No ( Successful Transfer? (Yes or No ( 1 Plate Yes no Yes Stab Tube no no no 2 Plate Yes no Yes Stab Tube Yes no Yes 3 Plate yes no Yes Stab Tube yes no Yes Control Plate no no no Stab Tube no no No Culturing and Aseptic Technique

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Experiment 2 Post-Lab Questions 1. Were all of your colony transfers successful? Explain what could have been the cause of any unsuccessful transfers. (5 points) I don’t think all of my colonies were transferred successfully. I think I could have fixed it bu taking entire colonies instead of some of it . 2. Did you have any growth that was different in appearance from the initial plates? What might account for any differences in growth on the transfer plate/tube? (5 points) The growth was different from the original experiment. These plates had a zig-zag form due to the way that I applied the colonies. But the growth around those zig-zags, looks like the bacteria were trying to branch out . 3. Describe why an unsuccessful transfer or growth of the transfer plate/tube differing from the initial plates would be a problem if this experiment were placed in a larger context (i.e., only one step in a longer experiment). (5 points) It could lead to inaccurate or inconsistent results . 4. Do some research and describe two or three scenarios in which it would be preferable to use a stab tube vs. a growth plate. ( Hint : What do bacteria use to help them move? Can motility be used to help identify many medically important pathogenic bacteria such as Enterobacteriaceae?) (5 points) Stab tubes would be tested to monitor motility in pathogenic bacteria because we could see how bacteria move around the stab. It also can be used when we want to study how a bacteria might grow under low-oxygen conditions. Cells might be inoculated in a liquid media or semi-solid media . Growth plates would be best used to observe certain feathers about bacteria. Grow bacteria cultures in agar plates will also allow us to separate the species of interest form other species present in the culture, we might also compare and study differences between species growth . Such as, E. Coli has a green glow to it, which is best seen on a growth plate, or you can use different agar to inhibit or encourage the growth of certain bacteria so you can isolate them for analysis . Culturing and Aseptic Technique

References Culturing and Aseptic Technique