Lab 24: Bacteriological Examination of Water

Question 1

What are some examples of human diseases that are transmitted by contaminated water?

Answer 1

cholera
giardiasis
cryptosporidiosis

Question 2

B/c of the cost and # of pathogens the test ONLY test for one kind of organism called

Answer 2

an indicator organism

Question 3

what was the indicator organism that we were testing for?

Answer 3

coliforms

Question 4

describe coliforms

Answer 4

• gram negative
• non-endospore forming bacillus
• ferments lactose w/ gas production
• facultative anaerobe

Question 5

what is the US EPA standard for drinking water?

Answer 5

0 coliforms/ 100ml

Question 6

Part 1 of coliform testing was the

Answer 6

presumptive test

Question 7

the lactose broth was inoculated w/ a

Answer 7

Durham tube

Question 8

Part 2 of coliform testing was the

Answer 8

confirmed test

Question 9

If the presumptive test was positive the sample was streaked on

Answer 9

EMB

Question 10

EMB is differential for

Answer 10

lactose fermentation

Question 11

Lac + results in

Answer 11

dark red colonies

Question 12

Lac - results in

Answer 12

pink/colorless colonies

Question 13

EMB is selective for

Answer 13

gram-negative bacteria

Question 14

on EMB coliforms produce

Answer 14

dark red colonies

Question 15

what does MPN stand for?

Answer 15

most probable #

Question 16

What is another test that can be done to test for microbial contamination in water samples

Answer 16

membrane filter method