Lab-5-Growth of Microorganisms

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American Military University *

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Dec 6, 2023

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Lab 5: Growth of Microorganisms (100 points) Student Name: Sylvester Dass Student ID: 5671874 Course ID: Biol 202 -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 citation 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. Why don’t microorganisms in cultures exhibit constant exponential growth? What are some steps you could take to extend the lifespan of a microbial culture? (5 points) In an experiment where the area of growth cannot be made perfect to aid in the growth, microorganisms will reach a point of peak growth ability. These areas include: Correct temperature for ideal growth, available nutrients in the quantities needed, amount of oxygen, and the ability to remove waster out of the farming area. 2. Using a textbook or a reputable online source, describe how lab cultures are maintained in a continual pattern of growth. Focus particularly on those used in biotechnology, such as E. coli, which is used to make human insulin. (5 points) Maintaing lab cultures in a continual pattern of growth requires several key components to ensure cells are provided with the necessary nutrients and conditions for optimal growth. These include: The inoculation and seed culture: There are preferred methods in doing this. For example, for f coli, the inoculum is usually stored as a frozen glycerol stock or freeze dried pellet, to preserve the strains genetic characteristics. It is then used to inoculate a seed culture which is placed in a nutrient rich medium to create a dense population. It is filled with large volumes of growth Growth of Microorganisms

medium as well. In some systems medium is continuously added to ensure optimal levels of nutrients. Fermentation: these cultures are placed into a vessel that is a controlled environment that creates the most optimal conditions for growth i.e temp, oxygen,pH, agitation. Quality control: this method is to ensure the desired growth and results are being achieved and things are monitored and changed to do so. 3. What are the four phases of bacterial growth in a closed system? (5 points) Lag Phase: Initial phase or stage where the bacterial population remains at a relatively constant size. Adaptation to the new environment is occurring here. Log Phase: Second phase also known as the exponential phase. This is where rapid bacterial growth takes place. Bacterial cells divide and reproduce at maximal rates but limited to the space and nutrient availability of the closed system. Stationary Phase: The third phase where the populations reach a stable size and growth slows drastically or stops. This is because of accumlilation of waste, nutrient depletion and limited space. Death phase: The fourth and final phase. This is just as the name says, the decline of bacterial population begins. Cell death rates drastically out weigh reproduction rates. 4. What are the physical and chemical methods of microbial control and what are the two methods used? (5 points) Heat treatment: can be done by way of autoclaving (high pressure steam at 250 degrees F or above or pasteurization: heating to levels that kill or inactivate harmful microorganisms. Filtration: physically separate microorganisms from liquids or gasses. Disinfection: Chemical agents to kill or inhibit the growth of microorganisms. Reduces microbial load on surfaces. Sterilization: This is used to eliminate or inactivate ALL forms of microorganisms to include bacterial spores. In the lab we used both Sterilization and disinfection. Growth of Microorganisms

5. You are a physician trying to isolate bacterial colonies from the human gut in attempt to diagnose a gastrointestinal infection. You streak your sample on a growth media containing glucose, amino acids, and salts that contain both sulfur and phosphorous with a pH of 7. You incubate the plates in aerobic conditions at 37 ˚C for three days, at which point you can see clear bacterial colonies forming on the plate. Would you feel confident in stating that you had successfully cultured all the bacteria from your gut sample? Explain why or why not? (5 points) I would not. This is because the environment created is exceptional for specific genes of bacteria. While some, thrive off of a mor acidic level or even a more alkaline level. Some bacteria even prefer higher temps as well. So given that there was successful growth, there is optimal growth. . Growth of Microorganisms

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