Lab Exam #2 Review

Question 1

Which tests should be used for G+ rods? (1)

Answer 1

LM (litmus milk)

Question 2

Which tests should be used for G+ cocci? (5)

Answer 2

1) BA
2) MSA
3) Coagulase (SA+; SE-)
4) SM-110
5) MS

Question 3

Which tests should be used for G- rods (6)?

Answer 3

1) SS
2) MAC
3) TSI
4) Citrate (EC-; EA+)
5) VP (EC-; EA+)
6) Methyl Red (EC+; EA+)

Question 4

Which tests should be used for G- cocci? (1)

Answer 4

1) SIM

Question 5

Which tests should be used for G- bacteria in general? (1)

Answer 5

EMB

Question 6

Which tests are differential only? (6)

Answer 6

1) LM
2) TSI
3) Citrate
4) VP
5) MR
6) SIM

Question 7

Which tests are selective only? (2)

Answer 7

Coagulase and BA

Question 8

Which tests are both selective and differential? (6)

Answer 8

1) SS
2) SM-110
3) MAC
4) MSA
5) MS
6) EMB

Question 9

List the enzymes the following tests look for the presence of, and state what each enzyme degrades:
1) DNase
2) Urea
3) Nutrient starch
4) LYS
5) Nutrient gelatin
6) Catalase
7) PHE
8) ONPG
9) Coagulase
10) MS

Answer 9

1) DNase: DNase, DNA
2) Urea: Urease, urea
3) Nutrient starch: Amylase, starch
4) LYS: Lysine decarboxylase, amino acid
5) Nutrient gelatin: Gelatinase, gelatin
6) Catalase: Catalase, H2O2
7) PHE: Phenylalanine deaminase, phenylalanine
8) ONPG: B-galactosidase; lactose fermentation
9) Coagulase: Coagulase, protein clotting
10) MS: Saccharase; sucrose

Question 10

What question does a NO3 (nitrate) test answer?

Answer 10

Does bacteria use NO3- as a terminal electron acceptor in anaerobic respiration (and denitrify it to N2)?

Question 11

1) What does a SIM test test for? (3 things)
2) What does an EMB test test for? (2 things)

Answer 11

1) SIM: Motility and H2S to FeS production (some G- cocci); indole production (from tryptophan breakdown) (EC+; EA-)
2) EMB: Ability to grow on EMB (G-) and coliform differentiation (by color and lactose fermentation)

Question 12

1) What does an SM-110 test test for? (3 things) What bacteria are positive?
2) What does an MS test test for? What bacteria are positive?

Answer 12

1) Ability to grow on NaCl (G+); gelatinase presence; glycolysis of fructose-phosphate from mannitol (G+ cocci: SA+; SE-)
2) Ability to grow on MS’s sucrose due to saccharase (G+ cocci: SM and EF+)

Question 13

What do the following tests look for?
1) Methyl red
2) VP
3) Citrate

Answer 13

1) Ability to ferment (make) mixed acids, decreasing pH (EC+, EA-)
2) Ability to ferment alcohol, creating intermediate acetylmethylcarbinol (EC-; EA+)
3) Ability to grow on citrate which releases ammonia, increasing pH (EC-; EA+)

Question 14

What does a TSI test look for? (3 things)
Include the color of each thing

Answer 14

1) Ability to ferment glucose (red over yellow, K/A)
2) Ability to ferment lactose and/or sucrose (all yellow, A/A)
3) H2S production (black)

Question 15

What does an MAC test look for? (2 things)
Include what species are positive for each thing.

Answer 15

1) Ability to grow on MAC (G-)
2) Ability to ferment lactose (EC+, red)

Question 16

What does an SS test look for? (3 things).
Include what species are positive for each thing.

Answer 16

1) Ability to grow on SS (G- non-coliform rods)
2) Ability to ferment lactose (EC+, red)
3) H2S production (Salmonella+)

Question 17

What does an MSA test look for? (2 things)
Include what species are positive for each thing.

Answer 17

1) Ability to grow on MSA (G+ cocci: Bacillus and staphylococcus)
2) Ability to ferment mannitol (SA+)

Question 18

1) What genuses are a BA test differential for?
2) What question does a BA test answer?
Include which species are positive.

Answer 18

1) Staph and strep
2) Does bacteria do gamma, alpha, or beta hemolysis? (G+ cocci: SA does beta; SE does gamma)

Question 19

What 2 things does a LM test look for? Include what species is positive.

Answer 19

1) Ability to ferment lactose and produce acid, decreasing pH (Bacillus)
2) Ability to break down casein protein in milk

Question 20

1) What 2 tests use neutral red indicator?
2) What color is neutral red indicator when introduced to an acid?

Answer 20

1) SS and MAC
2) Red: acidic

Question 21

1) What 3 tests use phenol red indicator?
2) What color is phenol red when introduced to an acid?

Answer 21

1) MSA, TSI, Urea
2) Yellow: acidic

Question 22

1) What test uses litmus milk as an indicator? What color is it when positive?
2) What test uses methyl green as an indicator? What color is it when positive?
3) What test uses bromcresol purple as an indicator?
4) What test uses bromothymol blue as an indicator?

Answer 22

1) LM: litmus milk (white: acidic = +)
2) DNase: methyl green (clearing = +)
3) LYS: bromocresol purple (purple/black: basic = +)
4) Citrate: bromothymol blue (vivid blue: basic = +)

Question 23

Which 4 tests can help differentiate between Staphylococcus aureus (SA) and Staphylococcus epidermidis (SE)?
Report when each is positive and negative

Answer 23

1) Coagulase (TSB): SA+; SE-
2) BA: SA beta; SE gamma
3) MSA: SA+; SE-
4) SM-110: SA+; SE-

Question 24

Salmonella and shigella grow well on which two media?

Answer 24

MAC and SS

Question 25

1) What two bacterial species ferment mannitol (MSA test)? What color does this result in?
2) What two bacterial species do not ferment on MSA? What color does this result in?

Answer 25

1) S. aureus (SA) and B. subtilis (BS): turn yellow (acidic)
2) S. epidermidis (SE) and B. cereus (BS): stay red (basic)

Question 26

What 7 media can help differentiate between E. coli (EC) and E. aerogenes?

Answer 26

1) VP: EC-; EA+
2) Citrate: EC-; EA+
3) Indole: EC+; EA-
4) Methyl red: EC+; EA-
5) MAC: EC+; EA-
6) SS: EC+; EA-
7) SIM: EC+; EA-

Question 27

List the 3 media that use phenol red and what color they are when positive

Answer 27

1) MSA: Turns yellow when positive
2) TSI: Red is ‘k’, yellow is ‘a’
3) Urea: Turns red when positive