1. Briefly explain how you can determine the presence of coliform bacteria in a water sample. 2. What is the purpose of the confirmed test in an experiment designed to test for coliform bacteria? 3. Explain why it is of prime importance to analyze water supplies that serve industrialized communities. 4. When using Endo agar as the selective and differential media for the confirmed test, how would you know whether the test is positive for the presence of E. coli?
Added by Cheryl D.
Step 1
This test involves pouring a water sample into a test tube containing the tablet, incubating the tube for 30 to 36 hours, and observing for specific reactions that indicate the presence of coliform bacteria. Show more…
Show all steps
Your feedback will help us improve your experience
Josee Pacheco and 51 other Biology educators are ready to help you.
Ask a new question
Labs
Want to see this concept in action?
Explore this concept interactively to see how it behaves as you change inputs.
Key Concepts
Recommended Videos
1. In the confirmatory test of water for the presence of coliforms, what agar is used which contains methylene blue which inhibits gram-positive bacteria and therefore select for gram-negative bacteria? 2. List two reasons Escherichia coli are good indicators of water contamination? 3. Name 3 of the 5 parts that give the definition of a coliform. 4. In the bacteriological examination of water using a MPN test, what are the indicators for a positive tube? 5. Why do we test for the fecal contaminant indicator bacteria Escherichia coli instead of pathogens in the bacteriological examination of water? 6. What is the purpose of the Durham Fermentation Tube in the Most Probable Number Test with lactose broth 7. Use the Table 58.1 in your manual on page 166 to calculate the MPN index for the water sample with positive tube numbers of 4-3-2. 8. In the confirmatory test of water for the presence of coliforms, what agar is used which contains color indicators sodium sulfite and basic fuchsin? 9. What other completed tests are used to identify only E. coli and rule out other coliforms? 10. Does a positive Presumptive MPN test mean that the water is absolutely unsafe to drink, explain why?
Madhur L.
why are laboratory tests for bacterial pollution of waters directed to the detection of coliform bacteria and especially Escherichia coli?
Adi S.
If the concentration of $E .$ coli in a broth is between $10^{4}$ and $10^{6}$ cells per $\mathrm{mL},$ the best way determine the precise number of living cells in the sample, would be to a) use a counting chamber. b) plate out an appropriate dilution of the sample on nutrient agar. c) determine cell number by using a spectrophotometer. d) Any of these three methods would be satisfactory. e) None of these three methods would be satisfactory.
Recommended Textbooks
Biology for AP Courses
Objective Biology for NEET
Introduction to General, Organic and Biochemistry
Transcript
18,000,000+
Students on Numerade
Trusted by students at 8,000+ universities
Watch the video solution with this free unlock.
EMAIL
PASSWORD