Question

Answer these questions: 1. You are testing a river water sample. Your "original" plate shows 100 coliform colonies. Assuming you did the serial dilution correctly, how many coliform colonies would you expect to see on your 1:10 plate? Your 1:100 plate? Explain. 2. Coliform counts often increase dramatically in rivers and oceans near cities after rainstorms. Why? (do Internet research; use reputable sources; cite your sources appropriately in your answer) 3. Why must m-Endo broth or some similarly selective and differential medium be used to count coliforms; why not just place filters onto a TSA plate? 4. Describe several ways in which coliform bacteria are known to get into well water. (Do Internet research; use reputable sources; cite your sources appropriately in your answer) 5. Why do we test water for coliforms if they are not considered pathogenic?

          Answer these questions:
1. You are testing a river water sample. Your "original" plate shows 100 coliform colonies.
Assuming you did the serial dilution correctly, how many coliform colonies would you expect to
see on your 1:10 plate? Your 1:100 plate? Explain.
2. Coliform counts often increase dramatically in rivers and oceans near cities after rainstorms.
Why? (do Internet research; use reputable sources; cite your sources appropriately in your answer)
3. Why must m-Endo broth or some similarly selective and differential medium be used to count
coliforms; why not just place filters onto a TSA plate?
4. Describe several ways in which coliform bacteria are known to get into well water. (Do
Internet research; use reputable sources; cite your sources appropriately in your answer)
5. Why do we test water for coliforms if they are not considered pathogenic?

Show more…

Answer these questions:
1. You are testing a river water sample. Your "original" plate shows 100 coliform colonies.
Assuming you did the serial dilution correctly, how many coliform colonies would you expect to
see on your 1:10 plate? Your 1:100 plate? Explain.
2. Coliform counts often increase dramatically in rivers and oceans near cities after rainstorms.
Why? (do Internet research; use reputable sources; cite your sources appropriately in your answer)
3. Why must m-Endo broth or some similarly selective and differential medium be used to count
coliforms; why not just place filters onto a TSA plate?
4. Describe several ways in which coliform bacteria are known to get into well water. (Do
Internet research; use reputable sources; cite your sources appropriately in your answer)
5. Why do we test water for coliforms if they are not considered pathogenic?

Added by Timothy S.

Biology for AP Courses

Julianne Zedalis, John Eggebrecht

Instant Answer

Solved by Expert Jerelyn Nevil

06/17/2024

Step 1

Each step involves diluting the sample by a fixed quantity or volume ratio. In this case, the dilution ratios are 1:10 and 1:100. If the "original" plate shows 100 coliform colonies, to predict the number of colonies on the 1:10 plate, you divide the original Show more…

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Transcript

00:01 Okay, so i see that you need help with each one of these questions, and it says you're testing a river sample.

00:05 Your original plate shows 100 coliform colonies.

00:10 Assuming you did the serial dilution correctly, how many coliform colonies would you expect to see on your 1 to 10 plate? your 1 to 100 plate, explain.

00:23 So, serial dilution is a process used to dilute substance into a stepwise manner.

00:33 Each step involves diluting the sample by a fixed quantity or volume ratio.

00:40 In this case the dilution rate ratios are 1 to 10 and 1 to 100.

00:52 If the original plate shows a hundred coliform colonies to predict the number of colonies in the 110 plate you divide the original number by the dilution factor.

01:04 Therefore a 100 colonies divided by 10 equals 10 colonies.

01:12 Let me just fix that writing, sorry.

01:25 Similarly, for the 1 -100 plate, you divide the original number by 100, resulting 100 colonies divided by 100 equals 1 colony.

01:40 I spelled that wrong, sorry.

01:48 This assumes a perfect dilution in plating technique.

01:56 Coliform counts often increase dramatically in rivers and oceans near cities after rainstorms.

02:03 Why? do internet research? use reproducible sources? cite your sources appropriately in your answer.

02:11 So coliform counts often increase in rivers and rainstorms near cities after rainstorms due to a runoff.

02:27 Increase is due to runoff.

02:38 Rainwater overflowing the ground surface picks up contaminants from urban areas, including fecal matter from pets and wildlife, fertilizers, and sewage overflows carrying them into the water bodies.

03:20 This phenomenon is exaggerated in cities due to the high amount of impervious surfaces like roads and sidewalks that do not allow water to seep into the ground...

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