BIOL 3053 Lab 6 Assignment (Winter 2022) (1) (1)

Memorial University of Newfoundland Department of Biology Biology 3053 Lab 6 Assignment PHYSICAL AND CHEMICAL METHODS TO CONTROL MICROORGANISMS Winter 2022 Name: Julie Hollahan Student #: 201311107 General Instructions: Type your name and student number in the above spaces. This assignment is due before 12 midnight on the day you will do Lab 7 as we will discuss the class results for the antiseptics/disinfectants exercise and is worth 2% of your lab grade . Read each question carefully. Type your answers in the space provided. When completed save your document as a pdf file and upload it into the Lab 6 Assignment Folder under Assessments – Assignments in the Brightspace shell. Once uploaded no changes to the assignment can be made. If you experience technical difficulties, contact the client Support Team of the Centre for Innovation in Teaching and Learning at www.citl.mun.ca/support Notice from Memorial University: You agree to the following; “All members of the Memorial University of Newfoundland community, including students, faculty, and staff, shall treat others with respect and fairness, be responsible and honest, and uphold the highest standards of academic integrity. By submitting this assignment, I unequivocally state that all work is entirely my own and does not violate Memorial University's Academic Integrity policy.” 1

OTHER INSTRUCTIONS : 1. As you go through the lab exercises, have your textbook and the appendices required for this lab available as these sources may help you to do the written assignment. 2. DO NOT copy and paste information from the lab or other material when answering your questions! This will be considered plagiarism and you will receive a grade of zero with possible further disciplinary action as per the University Calendar. Type your assignment in your own words ! 3. Read each question carefully and put your answers in the space provided. The spaces assigned for each question was just arbitrarily set to divide up the questions in the worksheet. You may use more or less of that space. 4. SAVE your document frequently. Once completed, save your assignment as a PDF document and upload your assignment to the Assignment Folder entitled “ Lab 6 Assignment ” in the pull down menu under Assessments. 5. If you have any questions, please contact your lab instructor through Brightspace OR through email: Sylvia at sbartle@mun.ca ; Kate at katecarson@mun.ca or Elizabeth at ediegor@mun.ca . EXERCISE 12: PHYSICAL METHODS TO CONTROL MICROORGANISMS 2

D. UV Radiation Fill up the table with your Results and Observations. (2.0 marks) Plate # Sketch of Plate Description of Growth 1 “C” (control) growth is good, yellow in color, growth covers the entire plate 2 (1 min. without cover) growth is absent where the E opening was placed where the UV rays were able to penetrate. Good growth where the UV rays were unable to penetrate the plate and covered unexposed are of the plate. growth yellow in color. 3 (3 min. without cover) Growth was absent where E-card opening was and UV rays were able to penetrate the plate. Good growth where E card covered the plate and UV rays not able to penetrate, growth yellow in color 4 (3 min. with cover) Entire plate covered with good, yellow growth 2. Explain, in your own words, the basis of the exercises on Dry and Moist Heat and Filtration, as set out in their introductions (i.e. How do they kill the cell?) (2.0 marks) 4

a. Dry Heat: kills the cells by the process of a reaction with oxygen, termed oxidation. This process involves denaturing enzymes and dehydrating microbes and endospores. It involves placing the specimen in hot temperatures that are lacking or lack water vapor in its air, making it “dry”. b. Moist Heat: involves using extremely hot temperatures and high pressure, such as an autoclave. This process essentially alters the membranes of the cell and denatures its proteins, which are crucial for the survival of the cell. c. Filtration: does not necessarily kill the cell. Filtration involves removing bacteria from a specimen by using membrane filters to separate the bacteria. This is done by using different size pore filters, allowing bacteria of different sizes to either pass or not pass through. Bacteria are usually more negatively charged and the filters used are usually more positively charged, therefore the negative bacteria are attracted to the positive filters, allowing them to more successfully be filtered out of the solution. d. UV Light Exposure: this alters the composition of the cell's nucleic acid by causing a mutation by introducing pyrimidine dimers that are responsible for changing the DNA sequence of the cell, resulting in the death of the cell. 3. Explain how the results you obtained in these exercises demonstrated these outcomes. If your results did not show these outcomes, explain how this could have occurred. (3.5 marks) a. Dry Heat: Incineration was used for this experiment. Growth was present before incinerating the specimen but was absent afterward. This shows that cell death occurred and no growth was able to happen due to incineration. b. Moist Heat: The autoclave was used for this experiment. Growth was present before autoclaving the specimen , but afterward, there was no growth noted on the plate. Therefore autoclave was successful in killing the cells. c. Filtration: Growth was present before filtering the specimen, but growth was absent after filtration. This shows that filtration was successful in removing the bacteria from the specimen that we were evaluating. d. UV Light Exposure: growth was present where UV light was unable to penetrate the plate, whereas growth was absent in areas exposed to the UV light. A card with a cutout “E” was used to demonstrate this, as growth occurred in the border of the E, but the cut-out E, where the UV light was able to penetrate the plate, was absent. 4. Why was a control plate inoculated and incubated before the test culture was sterilized? (1 mark) - A control plate was inoculated and incubated before the test culture was sterilized to promote the growth of the microbe to show that growth would occur before manipulating the specimen. This is so that we can compare the results once the specimen is attempted to be sterilized, to see if this method of sterilization is effective or not. 5

Javex half strength E. coli + 0 0 0 0 Ev1s10 B. subtilis + + + 0 0 Javex full strength E. coli + + + 0 0 Ev&s10 B. subtilis + + + 0 0 Lysol household E. coli + 0 0 0 0 Ev&s1 B. subtilis + 0 0 + + Lysol 100% E. coli + + 0 0 0 Ev5&s1 B. subtilis + 0 0 0 0 Spray Nine E. coli + 0 0 0 0 Ev1 B. subtilis 0 0 0 0 0 Ethanol 25% E. coli + + + + + Not effective for both vegetative cells and spores B. subtilis + + + + + Ethanol 70% E. coli + 0 0 0 0 Ev1 Not effective for spores B. subtilis + + + + + Neutra Quat E. coli + + 0 0 0 Ev5&s1 B. subtilis + 0 0 0 0 Hydrogen Peroxide E. coli + 0 0 0 0 Ev1 Not effective for spores B. subtilis + + + + + 2% Tincture of Iodine E. coli + 0 0 0 0 Ev1 Not effective for spores B. subtilis + + + + + Scope E. coli + + 0 0 0 Ev5 Not effective for spores B. subtilis + + + + + Listerine E. coli + 0 0 0 0 Ev1 Not effective for spores B. subtilis + + + + + No Growth = 0; Growth = +. B. subtilis represents spore-formers, E. coli represents vegetative cells. Effectiveness: E V = Effective for vegetative cell ; E V&S = Effective for vegetative cells and endospores . Effectiveness should also include the time taken, e.g. E v&s 5 or E v 1 s 5. 2. Let’s establish our criteria for the effectiveness of a chemical agent for disinfection. (0.5 mark) (a) Should the chemical agent be effective for vegetative cells, endospores or both ? (Circle or underline one) 7

(b) What length of exposure would you regard as most effective when treating materials for your patients? 1 minute , 5 minutes, 10 minutes, 15 minutes (Circle or underline one) Therefore, to be effective a chemical agent should affect both vegetative cells and spore s in a time of 1 minute (s). 3. Based on the effectiveness criteria we just established in Question #2 (see your table of results): (1 mark) (a) which chemical agent(s) are an effective disinfectant or antiseptic? - Based on these findings Spray nine and Lysol (disinfectant) 100% are effective. (b) which chemical agent(s) are not an effective disinfectant or antiseptic? - all others were not an effective disinfectant. Of course, chemical agents that are not effective as disinfectants may be very effective as antiseptics which are not expected to kill endospores and are expected not to damage living tissues while lowering the levels of bacterial cells on them. 4. Look up as many of the agents used in this Exercise as you can from Table 1 (Lab 6, page 98) and state their category (Antiseptic/Disinfectant) and list their use. (Hint: 5 of the chemical agents used in this experiment are found in Table 1.) (1 mark) Agent Name Category Use Javex (Sodium hypochlorite) Disinfectant external surfaces Lysol Disinfectant external surfaces Ethonal (alcohol) antiseptic skin Hydrogen peroxide antiseptic superficial skin infections Inodine antieptic skin 5. For three of the chemical agents, you examined two concentrations. (1.5 marks) (a) What did you expect to be the effect of increasing concentration for each particular substance Antiseptic/Disinfectant? - I expected that increasing the concentration of the substance would increase its effectiveness. 8