Coliform Bacteria Testing Procedures

The video tutorial discusses the role of E. coli in public health, its function as an indicator species, and the methods for testing water samples for bacterial contamination. It covers the preparation and analysis of samples using the membrane filter technique, incubation, and counting of bacterial colonies to assess water quality.

What is the primary role of E. coli in the intestines of endotherms?

• To produce toxins

• To cause digestive distress

• To aid in food digestion

• To act as a pathogen

Why is E. coli used as an indicator species in water testing?

• It is the only bacterium found in water

• It is difficult to detect

• Its presence indicates potential contamination by other pathogens

• It is harmless and always present

What is the purpose of the membrane filter technique in water testing?

• To detect the presence of coliform bacteria

• To remove all bacteria from water

• To sterilize the water sample

• To measure the pH of the water

What color indicates the presence of total coliform bacteria after incubation?

• Dark blue

• Green

• Yellow

• Blue or red with a metallic sheen

What should be done before pouring the sample into the filter during preparation?

• Ensure the filter membrane is in place

• Add more nutrient broth

• Turn on the vacuum pump

• Mix the sample with soil

Why is it important to avoid trapping air bubbles between the membrane and the pad?

• It will change the color of the colonies

• It will make the sample sterile

• It may lead to inaccurate colony counts

• It can cause the bacteria to die

At what temperature should the total coliform plate be incubated?

• 25°C

• 35°C

• 44.5°C

• 50°C

How should coliform counts be reported if 50 mL of sample is used?

• Multiply by 10

• Multiply by 5

• Multiply by 1

• Multiply by 2

What is the significance of counting only red and blue colonies for total coliforms?

• They are the only colors that appear

• They indicate the presence of viruses

• They represent non-coliform bacteria

• They specifically indicate total coliform bacteria

What is the final step before leaving the lab after completing the coliform analysis?

• Label the Petri plates

• Wash your hands

• Turn off the incubator

• Count the colonies again