Calculate the doubling time of a culture of E. coli that is started with 3x105 CFU/mL and grows to 4.6x108 CFU/mL in 3 hours. Be sure to use units in your answer.

The following results were obtained from a disk diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. Use these data to answer questions. The following results were obtained using the Kirby-Bauer method to assess microbial susceptibility to antibiotics. Staphylococcus aureus was the experimental organism. Use the data below to answer the questions. antibiotics Zone of Inhibition TO 3mm В. 7mm C Omm 10mm The most effective antibiotic was: Select one: O TO B. can't tell O O O O O

In growing E.coli, why is that (reasons) they do not grow after doubling time under 20 degrees celsius and under 37 degrees celsius, the number of colonies after doubling time has decreased? provide reliable sources (links).

Use the attached image to help explain the results on the NA and ECM plates. Be sure to address why each sample is either able or unable to grow on each plate and include the genotype(s) of the cells which are capable of growth.

To determine the number of cells in a pure culture of Klebsiella pneumoniae, you have performed a serial dilution using three tubes of sterile saline (9.9 ml each). A sample of 0.1 ml from the culture was added to tube 1. Similarly, 0.1 ml from tube 1 was used to inoculate tube 2, and tube 3 was inoculated using 0.1 ml from tube 2. A nutrient agar plate was then inoculated using 0.1 ml from tube 3 and incubated overnight. The next day, 92 colonies were observed on the plate. How many cfu/ml were in the original culture? Using a Petroff-Hauser counting chamber, the number of cells in the same culture was estimated to be 8.5 • 109 cells/ml. How can you explain these results?

The number of bacterial cells in a culture broth is to be determined by a culture technique. Serial dilutions were performed and a 1 mL aliquot from each dilution was mixed with warm molten agar and poured into a Petri dish. The numbers of bacterial colony forming units (CFU) after overnight incubation are shown in the table below. What is the number of colony forming units per mL of the culture broth? Choose only the most appropriate plate for your calculation. Give your answer as the number only (do not add text for the units). You may use scientific notation with the format 1.12e+6 (that is, 1.12 x 106 cfu/mL). (Note: Canvas will then display your answer a whole number.) Plate Dilution Plate 1 10 dilution Plate 2 10 dilution -5 Plate 3 10 dilution Plate 4 10 dilution Plate 5 107 dilution -8 Plate 6 100 dilution *Too many to count Number of colony forming units (CFU) TMTC* TMTC* TMTC* 867 154 18

A new intestinal isolate of E. coli is known to have a generation time of 12 minutes. If a culture contained 3, 221,225,472 bacterial cells after 6 hrs how many bacteria must have been inoculated into the culture at time 0.

The thermal death time in an autoclave at 121oC for a microbial culture was thirteen minutes. The thermal death time for another sample of the same culture in a hot-air oven at 121oC was twenty-one minutes. Use your knowledge of what thermal death time measures to identify which method of heating was more effective against this microbial culture. The hot-air oven treatment was more effective. The autoclave treatment was more effective. Both thermal death times were equally effective. Not enough information is provided to determine effectiveness.

Diagram illustrating Miles & Misra technique for determining viable counts: 10ul 10-5 106 104 10-7 3. Set up controls of the donor and recipient cultures as follows: • Spread plate 0.1 ml of the donor culture over the surface of each of the 3 different selective media (i.e. nutrient agar + Ap; nutrient agar + Sm; nutrient agar + Rif) • Similarly spread plate 0.1 ml of the recipient culture over the surface of each of the 3 selective media • What is the purpose of this step?

How would you produce a 10^-1 dilution if a 3 mL bacterial sample using the entire 3 mL volume?  suppose your professor handed you a test tube with 2.0 mL of an E. coli broth culture in it and told you to make a 10^-1 dilution of the entire culture. Explain how you would do this. Show your calculations.