Coliforms and MPN Testing Methods

The video tutorial explains the Most Probable Number (MPN) method, used for estimating viable cell counts in diluted samples, such as water from rivers or beaches. It highlights the importance of detecting coliforms, bacteria that utilize lactose, to assess water quality. The tutorial provides a detailed lab procedure for MPN, including sample preparation, incubation, and result interpretation. It also guides using the MPN table to determine viable cell counts and confidence limits, helping to assess water contamination levels.

What is one reason to use the Most Probable Number (MPN) method?

• To calculate the salinity of water

• To determine the temperature of water

• To detect the presence of coliforms in diluted samples

• To measure the pH level of water

Why are coliforms important in water quality testing?

• They help in oxygenating the water

• They indicate the presence of heavy metals

• They are a sign of chemical pollution

• They can suggest fecal contamination

What is a coliform?

• A chemical compound

• A type of virus

• A type of algae

• A bacterium that can use lactose

What is the first step in the MPN laboratory procedure?

• Incubate the samples overnight

• Use the MPN table to interpret results

• Add 0.1 milliliters of water sample to tubes

• Prepare the water sample by adding 10 milliliters to tubes

What is the purpose of incubating the water samples overnight in the MPN procedure?

• To allow chemical reactions to occur

• To enable the growth of coliforms

• To sterilize the samples

• To measure the temperature change

What is the significance of using different volumes of water samples in the MPN test?

• To assess growth at different dilutions

• To test different pH levels

• To measure the salinity of the water

• To ensure accurate temperature readings

How do you determine the number of viable cells using the MPN method?

• By checking the color change in the sample

• By using the MPN table with growth data

• By counting the number of cloudy tubes

• By measuring the pH of the sample

In the MPN test, what does a cloudy tube indicate?

• Presence of viable coliforms

• Absence of bacteria

• High pH level

• Presence of heavy metals

What does the MPN table provide besides the number of viable cells?

• The exact number of coliforms

• The pH level of the water

• The statistical confidence limits

• The temperature of the water

What does a 95% confidence limit in the MPN table mean?

• The exact number of coliforms present

• The range within which the true number of coliforms likely falls

• The percentage of water that is contaminated

• The temperature range of the water