You have observed the following data from an aerobic plate count. How many bacteria are in the undiluted sample? Dilution Average CFUs/ml 10-8 TNTC (too numerous to count) 10-9 334 10-10 111 10-11 27 10-12 5
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You have observed the following data from an aerobic plate count. How many bacteria are in the undiluted sample?
| Dilution | Average CFUs/ml |
| 10-8 | TNTC (too numerous to count) |
| 10-9 | 334 |
| 10-10 | 111 |
| 10-11 | 27 |
| 10-12 | 5 |
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- After incubating for 24-48 hours, you retrieve your 4 agar plates for the osmotic pressure exercise from the 37°C incubator. You observe the following results: • Sa = Staphylococcus aureus • Pv = Proteus vulgaris Sa For each organism, you should indicate in the text box below: 1. At what salt concentrations (osmotic pressures) you saw growth. 2. The classification term you would use in order to classify the organism based on osmotic pressure. Choose your term based upon where you observed growth; not optimal growth. Each organism has only one classification term associated in describing its growth pattern(s). You will need to use the osmotic pressure classification descriptions and terms outlined in your lab manual.The number of bacteria in saliva samples was determined by collecting the saliva, making serial dilutions, and inoculating nutrient agar by the pour plate method. The plates were inoculated aerobically for 48 hours at 37°C. What can you conclude from this data? Why? Mouthwash CFU per ml in salvia Before Use After Use Listerine 2.22 x 107 1.22x107 Schmidts Mouthwash 2.42 x 107 3.22x105 Biotene Mouthwash 3.21 x 107 2.12 x106t /g = (Log Nt – Log N0) /0.301 I introduce a loopful of Escherichia coli cells (say, 1000) into 10 mL of Nutrient Broth at 8 p.m. the night before your lab. The cells were taken from a culture plate (Nutrient Agar) held at 37°C, and inoculated into broth at the same temperature. They were held at 37°C overnight in a shaking water bath. At what time would the culture reach the Stationary Phase? Recall that doubling time under optimal conditions (these are) is 20 minutes. A growing bacterial culture has 10,000 CFU/mL at noon and 10,000,000 CFU/mL at 6 p.m. What is the generation time under these conditions? What are your assumptions? At midnight you inoculate 10 mL of a culture of Enterococcus with 103 cells/mL into 990 mL of the same medium, held under the same conditions as the original culture. At what time would the culture reach 107 cells/mL? Assume exponential growth over the period. Assume that g=half an hour. Note: We worked a different variant of this problem in…
- The solution containing bacterial spores is heated in an autoclave. When the autoclave has reached a constant temperature of 121 °C, there are still 106 spores/ml. The specific death constant for bacterial spores at 121 ° C is 11.62 min-1. How long should the heating be continued at a constant temperature so that there are 1 spores/ml left? Enter the answer in minutes to three decimal places.After taking an aliquot of your cells and diluting them with Trypan Blue in a 1:1 dilution, you load the cell/Trypan mixture onto a hemocytometer to count the cells. You obtain the following counts: Quadrant Transparent cells Blue cells 1 2 3 4 LO 65 5 71 68 73 2 4 1 3 67 4) If your original cell culture (the one you took an aliquot from to count) has 13 mL of cell suspension, what is the total number of cells you have in culture? Provide your answer as the full number 2A bacterial culture has a concentration of 3.2 x 108 cells /mL. You dilute this culture as follows: 1/50, then 10-3 and finally 1/20. If you then plate 0.2 mL of the final dilution, how many CFU would you expect following incubation?
- 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 AgarA laboratory technician performed a series of 10 fold serial dilutions shown below. he plated 0.1 mL from each dilution tube onto NA and got the follow numbers per plate dilution 1:10 1:10 1:100 1:1000 1:10000 1:100000 colony count >1000 >1000 808 303 38 3 calculate the concentration of bacteria in the undiluted stock (in CFU/mL)Determine what percentage of the culture was living (viable) and what percentage was dead (mortality). Plates Plate Dilution Volume plated No.of colonies Avg No Concentration of diluted sample Cd(cells/mL) Concentration of original sample Cu(cells/mL) 1 10^-3 10ul R1=130,R2= 110,R3=210 150 150mL 1.50*10^6 Volume of cells(mL) Volume of diluent(mL) Total dilution(D) Hemocytometer count Avg cells in 1 mm^2 area Concentration of diluted sample Cd(cells/mL) Concentration of original sample Cu(cells/mL) 4.3 0.5 0.1 grid 1= 171 , grid2 = 185 178 1.78*10^5 1.78*10^6
- A culture is incubated for 10 hours. 1 hours after inoculation it reached the exponential growth phase. At this time point the cell density was 1x10^4 cells/ml. 5 hours after inoculation (still during the exponential growth phase) the cell density was 1x10^7 cells. Calculate K and g(t). The growth constant (k) is minute. (round to 3 decimal points) The generation time (gt) is minutes. (round to whole number)Assume an inoculum with a cell density of 108 cells per mL. The entire generation time takes 30 minutes. How many hours would it take to grow a culture to 108/mL if you started with a 10–2 dilution? helpful formula: g (generation time) = 0.301 (time)/ log x – log xoA lab technician is working with a bacterium in pure culture (in 5 ml of liquid media in a test tube). The bacterium is a mesophile that can infect humans. Which of the following is NOT true (with regards to temperature conditions for this bacterial culture)? Lowering the temperature to -10 deg C for at least an hour will likely kill all the bacteria. Placing the tube at 37 deg C will likely facilitate rapid growth of the bacteria. Raising the temperature to 90 deg C for at least an hour will likely kill all the bacteria. Placing the tube at 4 deg C will likely slow or halt growth of the bacteria.