I need help with how to get to the answer. I have the answers (are below the question) but don't know how to get to it. So please show what was done to get to it.
1)You are asked to determine the concentration of a bacterial culture. You take 1.0 mL of the culture and add it to 4.0 mL of water (Tube #1). You then take 1.0 mL from Tube #1 and add it to 14 mL of water (Tube #2). Finally, you take 1.0 mL from Tube #2 and add it to 19 mL of water (Tube #3). You then spread 0.20 mL from Tube #3 onto a nutrient agar plate and incubate the plate at 37ËC. After 24 hours, you count 215 colonies on the plate.
a) By what factor has the original culture been diluted in Tube #1? (1 point)
Ans.5
b)By what factor has the ORIGINAL culture been diluted in Tube #2? (1 point)
Ans..75
c)By what factor has the ORIGINAL culture been diluted in Tube #3? (1 point)
Ans. 1500
d)What is the concentration of the original bacterial culture? Include proper units.
Ans.1,612,500 CFU/ml
I need help with how to get to the answer. I have the answers (are below the question) but don't know how to get to it. So please show what was done to get to it.
1)You are asked to determine the concentration of a bacterial culture. You take 1.0 mL of the culture and add it to 4.0 mL of water (Tube #1). You then take 1.0 mL from Tube #1 and add it to 14 mL of water (Tube #2). Finally, you take 1.0 mL from Tube #2 and add it to 19 mL of water (Tube #3). You then spread 0.20 mL from Tube #3 onto a nutrient agar plate and incubate the plate at 37ËC. After 24 hours, you count 215 colonies on the plate.
a) By what factor has the original culture been diluted in Tube #1? (1 point)
Ans.5
b)By what factor has the ORIGINAL culture been diluted in Tube #2? (1 point)
Ans..75
c)By what factor has the ORIGINAL culture been diluted in Tube #3? (1 point)
Ans. 1500
d)What is the concentration of the original bacterial culture? Include proper units.
Ans.1,612,500 CFU/ml
Related textbook solutions
Related questions
You are trying to determine the approximate bacterial count in a sample of soil. You weigh out 1 gram of soil and add it to 9ml water (tube 1). You then take 1 ml out of tube 1 and place it in 9ml of water in tube 2. Finally, you take 1 ml out of tube 2 and place it into 9 more ml of water in tube 3. You plate out 1.0 ml of the contents of tubes 1, 2 and 3 onto PCA, incubate both for two days, and observe the results. (*Note: 1g= 1mL)
| Plate contents | Number of colonies observed |
| Tube 1 | 532 |
| Tube 2 | 43 |
| Tube 3 | 6 |
Calculate the CFUs present in the orginal (undiluted) soil sample. Show your calculations.
