Lab Final Flashcards by Samantha Boyer

EMB

positive vs negative

positive: dark, opaque purple/pink colonies

negative: transparent or no growth

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EMB

what changes color?

eosin

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EMB

selective
differential

selects against GPs via eosin and methylene blue

differential for lactose fermenters via lactose

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EMB

enzyme needed for positive

B-galactosidase

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EMB
green sheen organisms

E. coli
C. freundii
K. pneumoniae

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MacConkey
positive vs negative

pos: pink/red color
neg: no cc

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MacConkey
what changes color?

neutral red

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MacConkey
selective
differential

selects against GPs via bile salts and crystal violet
differential for lactose fermenters via lactose

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MacConkey
enzyme needed for positive

B-galactosidase

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TSIA
3 sugars present
least abundant

glucose (least abundant), lactose, sucrose

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TSIA
results

K/K: no fermentation
K/A: glucose fermentation only
A/A: glucose, sucrose or lactose fermentation
gas pos/neg
H2S pos/neg (black)

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TSIA
alkaline reversion

yellow goes back to red on slant
alkaline products of AA metabolism after glucose runs out; requires O2

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2 molecules leading to H2S production

cysteine
thiosulfate

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molecule that reacts with H2S to give black color

Fe(NH4)2(SO4)2 x 6H2O

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TSIA
A/A organisms

E. coli
K. pneumoniae
P. vulgaris

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SIM
pos/neg indole
reaction?

pos: red color after indole test with Kovac’s reagent
neg: no cc
converts tryptophan to indole

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SIM
enzyme needed for pos indole

tryptophanase

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SIM
indole pos organisms

E. coli
P. vulgaris

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MR
sugar fermented

glucose

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MR
pos/neg
pos rxn

pos: red after addition of methyl red
neg: no cc

mixed acid fermentation

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MR
pos organisms

E. coli
C. freundii
M. morganii
P. vulgaris
S. enterica
S. flexneri

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Citrate
pos/neg
rxn

pos: blue
neg: green

use of citric acid as sole source of carbon and energy

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Citrate
what happens to pH if citrate is consumed?
indicator

goes up
bromthymol blue

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Citrate
pos organisms

B. mageterium
C. freundii
K. pneumoniae
K. aerogenes
K. oxytoca
all non-fermentatives except S. paucimobilis

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**Citrate** enzyme needed for pos

citrase

**Thiogel** pos/neg pos rxn

pos: gelatin liquifies neg: gelatin remains solid hydrolysis of gelatin

**Thiogel** what kind of polymer is gelatin?

protein

**Thiogel** pos organisms

P. aeruginosa P. fluorescens

**Phenylalanine** pos/neg pos rxn

pos: green color after addition of FeCl3 neg: no cc deamination of phenylalanine

**Phenylalanine** what does reagent detect?

phenylpyruvic acid

**Phenylalanine** enzyme needed for pos

deaminase

**Phenylalanine** pos organisms

M. morganii P. vulgaris

**Nitrate** pos/neg

pos: N2 gas in tube; red color after A & B regents; no cc after zinc neg: red after zinc

**Nitrate** end product if red after A & B

NO2 - nitrite

**Nitrate** negative indicates...

no reduction of nitrate

**Nitrate** end product if no cc after zinc

NH3 or R-NH2

**Nitrate** enzyme needed for pos

nitratase/nitrate reductase

**Nitrate** N2 organisms neg organisms

N2: P. aeruginosa; P. stutzeri neg: A. calcoaceticus; A. faecalis; S. paucimobilis

**Urease** pos/neg pos rxn

pos: bright pink neg: no cc hydrolysis of urea

**Urease** end products of urea hydrolysis

CO2 and ammonia

**Urease** what causes cc?

phenol red pH rises

**Urease** pos organisms

M. morganii P. vulgaris

**VP** pos/neg pos rxn

pos: red after VP A and B neg: no cc organism produces acetylmethyl carbinol from glucose fermentation

**VP** pos organisms

S. marcescens Enterobacter aerogenes

**Starch** pos/neg pos rxn

pos: clearing around colonies after Lugol's iodine neg: no clearing starch hydrolysis

**Starch** enzyme needed for pos

a-amylase oligo-1,6-glucosidase

**Starch** pos organisms

B. cereus B. subtilis B. mageterium

**Starch** iodine reacts with starch to form...

dark brown color

**Litmus milk** 5 things it can tell us

1. litmus reduction 2. clotting of casein 3. digestion of casein 4. acid from lactose ferm 5. gas

**Litmus milk** pH indicator

litmus

**litmus milk** white result

litmus reduction due to anaerobic respiration

**Litmus milk** pink result

acid; lactose fermentation

**Litmus milk** clear fluid in top of curd

whey

**Litmus milk** curd result

stormy fermentation

**Litmus milk** pos organisms

B. cereus (curd) L. acidophilus (pink, curd)

**Litmus milk** blue result

proteolysis giving ammonia alkaline

**Litmus milk** ----- converts casein to paracasein, soft curd

renin

**Litmus milk** clearing of media result

proteolysis

**OF** test ingredients

tryptone bromothymol blue a sugar

**OF** procedure with 2 tubes

one left open to air one covered with mineral oil

**OF** results

**OF** example organisms

fermenter (both yellow): E. coli oxidizer (yellow only in open tube): Pseudomonas non-saccharolytic (both green): Alcaligenes

are lactose fermenters typically pathogenic or non-pathogenic?

tend to be found in gut microbiome generally not pathogenic but can be opportunistic pathogens

arginine dihydrolase intermediate

agmantine

VP intermediate

acetoin

decarboxylase intermediate

cadaverine

phenylalanine intermediate

phenylpyruvic acid

gelatinase intermediate

oligopeptide

citrate slant intermediate

oxaloacetate

ONPG test is required for *Neisseria* because...

does not produce fermentation acid

Loeffler slant iron

absence of iron prevents DtxR from binding tox operator

VJ is to MSA as...

Salmonella-Shigella is to MacConkey

Hektoen tests for ferm of which sugar?

lactose

Ox + = facultative anaerobe

false