Lab quiz 4

Question 1

What are the properties of a coliform?

Answer 1

-Gram negative
-bacilli
-non spore forming
-produces gas by fermenting lactose

Question 2

How does the multiple tube method work?

Answer 2

Presumptive test
-use durham tube (collects gas) to see if the sample ferments

Confirmed test
-if the presumptive test comes back positive for fermentation, you t-streak your sample on EMB and look for coliform

Question 3

Why are coliform used as indicators?l

Answer 3

Because if a coliform is present it means the water is contaminated by fecal matter

Question 4

What is EMB differential for and selective for?

Answer 4

Differential for lactose fermentation & selective for gram negative

Question 5

What is MPN? What is the MPN standard set by the US EPA?

Answer 5

MPN is the most probable number per 100 mL of water.
The standard set is 0 coliform per 100 mL of water

Question 6

EMB

Answer 6

eosin methylene blue plate