Exercise 9: Background for Water Quality Flashcards
what is an indicator organism?
one which is present in human waster in high enough numbers to be readily detected and easy to find.
what is the most commonly used indicator?
the coliform bacteria
what are coliforms?
they are aerobic or facultatively anaerobic gram negative rods’ they do not form endospores, they ferment lactose which leads to acid and gas production within 48 hours of incubation at 35 degrees C.
how can coliforms be detected?
by using the multiple tube technique which involves two tests; a presumptive test and a confirmation test.
what does the presumptive test for?
acid and gas production.
what test is using to confirm?
the MUG agar ( methylumbelliferyl-B- D glucuronide) or EMB ( Eosin Methylene Blue) agar.
what does MPN stand for?
most probable number
how is the coliforms in a sample determined?
using the MPN method
