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- Are the large numbers of microorganisms found in the mouth cause for concern? Explain.
- How can you determine whether a culture or subculture is pure?
- What kinds of clinical speciments may yield a mixed flora in bacterial cultures?
- Why was a blood agar, rather than a nutrient agar, plate used for the culture from your mouth?
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- What is the major difference between an enrichment culture and a selective culture? Why are microbial doubling times in nature typically longer than those obtained in the lab? Briefly describe the following mechanisms of measuring bacterial growth: Direct microscopic cell count Plate count Most probable numberYou are given a 1 gram soil sample of unknown bacterial load. After doing 10-fold serial dilutions of the soil in sterile water, 100 uL volumes are taken from each dilution for preparation of pour plates. Following incubation, each half of the 10-8 plate has 46 colonies.a) What was the dilution factor?b) How many bacteria were present in the soil?2. Staphylococcus aureus divides every 20 minutes. A culture begins with 10 bacterial cells.a) After 5 hours, how many generations have occurredb) After 5 hours, how many bacteria are present?3. How many milliliters would you need to prepare a 10-2 dilution from a 10ml starting culture?In a bacterial culture on an agar plate, what is a zone of inhibition? An area where the growth of bacteria is increased compared to the rest of the agar plate An area where the growth of bacteria is prevented or reduced compared to the rest of the agar plate An area where the growth of bacteria is not affected compared to the rest of the agar plate An area where the the agar becomes contaminated with mold
- Can you please discuss the principles of using Motility Test Medium for the detection of bacterial motility. Focus on the components of the medium and the purpose of each component. Note: You may refer to different culture media manuals like Difco, BBL, etc.during inoculation, the bacterial culture tube is always held at an angle and the lid of the Petri dish is slightly open. Explain the purpose of these steps briefly.Using your fingers, you are asked to aseptically touch the surface of a sterile agar plate. Illustrate the possible result from this step if your fingers are (a) unwashed – touched various things prior to placing on agar surface, and (b) washed with soap or disinfected with 70% alcohol. Describe the relative abundance of microbial growth observed on the plates. List and draw the possible characteristics of an isolated bacterial colony that can be observed based on type of (a) margin, (b) elevation, (c) texture, and (d) optical property.
- A pure culture was inoculated onto a Mueller-Hinton agar plate. The Kirby-Bauer procedure was performed. One of the drugs tested showed a large zone of inhibition but also had small colonies growing within this zone. Further testing showed that these colonies were not the results of contamination. Why would these colonies be present within this zone of inhibition?A culture of E. coli has a concentration of 5 x 108cells/mL. How many times do you have todilute the culture so that when you spread 0.1mL on an agar plate you will have 250 colonies?Hint: you need to find dtotal and then convert it into a DF.You are transferring a bacterial culture from a tube of broth to a Petri dish containing trypticase soy agar. Please list the steps that are necessary to make the transfer successfully and with minimal risk. of contamination.
- A class of 15 students (8 males and 7 females) will need to culture an unknown bacteria for a specific activity where 5 nutrient agar pates per female student and 3 agar slants per males student are needed to prepare. agarplate: 25mL Agar slant: 10mL Broth tube: 8mL Nutrient Agar: Yeast extract: 2g/L peptone: 5g/L Sodium chloride: 5g/L Agar powder: 15g/LGiven the scenario, compute for the total volume of the culture media solution (milliliter or liter) and dehydrated media (grams). Scenario: The students of a Microbiology class were tasked to transfer or subculture a pure culture of Escherichia coli bacterium in five 7 mL nutrient broth and five petri dishes of nutrient agar with 20 mL capacity each. Based on the instruction bottles for nutrient broth and nutrient agar, preparation of the culture media is as follows. Nutrient broth: 8 g/liter Nutrient agar: 28 g/liter Formula: C1V1 = C2V2 *Concentration *Volume Computation: What are the answers to the following. Weight in grams of nutrient broth: _________ Distilled water in mL for nutrient broth: __________ Weight in grams of nutrient agar __________ Distilled water in mL for nutrient agar: ____________Describe characteristics of Streptococcus Agalactiae in the Agar: (How does colonies look like (color) and explain does it grow on that agar. (Don't have to write the incubation period) ~ Only describe how would it look like on the Agar: Blood Agar (Aerobic) MacConkey EMB PEA Mannitol Salt Agar Chocolate Agar Nutrient Agar