Lab of selective and differential media

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Virginia Commonwealth University *

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Biology

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Dec 6, 2023

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Lab of selective and differential media Honor statement: I, Lucas Aldridge , have reviewed the websites, figures, videos, and tests all on required websites. I have thoroughly read through the discussion sections for each lab. Task 3: Complete the following Discussion Questions on the template in RED. Be sure to source your responses after EACH question. 1. State the chemical nature and function of enzymes. Response: Proteins that act in substrate molecules and decrease necessary activation energy for chemical reactions to occur through stabilizing the transit state. Source: https://www.ncbi.nlm.nih.gov/books/NBK554481/#:~:text=Enzymes%20are%20proteins %20that%20act,happen%20at%20physiologically%20significant%20rates . (Access date: 9/6/2023) 2. Define endoenzyme and exoenzyme. Response: Endoenzyme: protein that works within the cell. Exoenzyme: protein that works outside the cell. Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) A. STARCH HYDROLYSIS 1. Describe a method of testing for starch hydrolysis and state how to interpret the results. Response: inoculate a half of a starch plate with an organism and the other half with another organism. Add iodine after incubation. If starch is hydrolyzed the iodine won’t react to the area around the bacterium, leaving the surrounding area clear. Otherwise, it will turn the agar a dark brown or black. Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) B. PROTEIN HYDROLYSIS 1. Describe a method of testing for casein hydrolysis and state how to interpret the results. Response: inoculate on divided skim milk agar plate with two inoculums and incubate. If casein is hydrolyzed by protease the agar will be clear, if not then opaque.
Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) C. FERMENTATION OF CARBOHYDRATES 1. Name the general end products which may be formed as a result of the bacterial fermentation of sugars and describe how these end products change the appearance of a broth tube containing a sugar, the pH indicator phenol red, and a Durham tube. Response: acid as well as gas are end products. With acid production the indicator will turn yellow, with gas production a bubble will form in the durham tube. Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) D. INDOLE AND HYDROGEN SULFIDE PRODUCTION 1. State the pathway for the breakdown of tryptophan to indole. Response: tryptophan is broken down by tryptophanase . Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) 2. State the pathway for the detection of sulfur reduction in SIM medium. Response: adding Kovac’s reagent and examining for a black color which indicates sulfur reduction. Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_08%3A_Using_Biochemical_Testing_to_Identify_Bacteria (Access date: 9/6/2023) 3. State three reactions that may be tested for in SIM medium and describe how to interpret the results. Response: sulfur, indole, and motility. Black indicates hydrogen sulfide, red indicates indole, and migration indicates motility. Source: https://bio.libretexts.org/Bookshelves/Microbiology/Microbiology_Laboratory_Manual_(Hartline)/01 %3A_Labs/1.23%3A_SIM_Deep_Tests (Access date: 9/6/2023)
Task 4: Answer the following questions pertaining to antimicrobial chemotherapy. Answers must be in RED. Be sure to source your responses after EACH question. A. DISINFECTANTS, ANTISEPTICS, AND SANITIZERS 1. Define the following terms: sterilization, disinfection, decontamination, disinfectant, antiseptic, and sanitizer. Response: 1) Sterilization: a process which kills all microorganisms on surfaces. 2) Disinfection: a process which kills harmful bacteria and viruses from surfaces. 3) Decontamination: a process to remove and kill contamination preventing infectious organisms from contaminating persons or lab equipment. 4) Disinfectant: agent used to disinfect surfaces and inanimate object, usually toxic to human tissue 5) Antiseptic: a chemical mixture that slows or stops microbial growth of surfaces, usually safe on human tissue. 6) Sanitizer: an agent the reduces but not necessarily eliminates, microbial numbers to safe levels. Source: https://bio.libretexts.org/Learning_Objects/Laboratory_Experiments/Microbiology_Labs/Microbiolog y_Labs_II/Lab_19%3A_Use_of_Chemical_Agents_to_Control_of_Microorganisms (Access date: 9/6/2023); https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7158362/#:~:text=Sterilization%3A %20Sterilization%20is%20defined%20as,various%20physical%20and%20chemical%20methods . (Access date: 9/6/2023) 2. State why chemical agents are usually unreliable for sterilization. Response: they work to slowly to kill viruses or other particularly resistant and tough organisms. Source: https://biocyclopedia.com/index/biotechnology_methods/microbiology/control_of_microorganisms_ by_using_disinfectants_and_antiseptics.php#:~:text=Because%20disinfectants%20and%20antiseptics %20often,destruction%20of%20all%20life%20forms ). (Access date: 9/6/2023) 3. List five factors that may influence the antimicrobial action of disinfectants, antiseptics, and sanitizers. Response: 1) Concentration of chemicals used. 2) temperature 3) the kinds of the microorganisms
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