Part 1: Litmus Milk is an undefined, differential medium that is utilized to differentiate microorganisms based on the use of its two main nutritional components - the milk sugar lactose and the protein casein. Litmus Milk also contains Litmus in the form of azolitmin as a pH indicator and redox indicator. Please respond to the following questions pertaining to the Litmus Milk Reactions:
Please list the four basic reactions that occur in Litmus Milk.
Suppose that you inoculated a Litmus Milk tube with a bacterium that is known to completely degrade casein. After incubation at 37°C for 24 hours, you observe a solid blue tube. Was this result expected? Provide an explanation for this result.
Part 2: We are currently discussing methods used to control bacterial growth. Please respond to each of the following prompts in your discussion submission and respond to at least one other student after your initial discussion submission.
In Chapter 16, sterilization was defined as the complete elimination of vegetative bacterial cells. Select one sterilization technique discussed in Chapter 16 and list at least one advantage/disadvantage.
In Chapter 17, we exposed Staphylococcus aureus, Escherichia coli, and XL1-Blue II cells to UV light (254 nm) at 20-second intervals. Which of these bacteria would you expect to be most sensitive UV sensitive vs. least UV sensitive? Explain.
In Chapter 18, we performed the Kirby Bauer test on Staphylococcus aureus and Escherichia coli on Mueller-Hinton agar plates. Suppose that we were testing the susceptibility of these bacteria against Antibiotic X. We placed discs impregnated with the same concentration of Antibiotic X on MH agar plates that had been swabbed with each bacterium, respectively. After 24 hours of incubation, you observed a zone of inhibition (ZOI) measuring 5 mm in diameter around the antibiotic disc on the E. coli plate and a zone of inhibition measuring 20 mm in diameter around the antibiotic disc on the S. aureus. Which of the two bacterium is most susceptible to Antibiotic X? Which of these zones of inhibition will have the lowest minimum inhibitory concentration (MIC)?
Sample Solution