Biochemistry & Unknown Identification

What temperature range do psychrophiles grow in?

-5°C to 20°C

What are psychrophiles?

Cold-loving organisms that grow in refrigerated conditions

What temperature range do mesophiles grow in?

20°C to 45°C

What type of organisms are most human pathogens?

Mesophiles

What is the optimal temperature for most mesophiles?

About 37°C

What temperature range do thermophiles grow in?

50°C to 70°C and above

Where are thermophiles commonly found?

Hot springs and compost

What pH do acidophiles prefer?

Below 6

What environments do acidophiles thrive in?

Acidic environments

What pH do neutrophiles prefer?

pH 6–8

What organisms are most common in lab settings?

Neutrophiles

What pH do alkaliphiles prefer?

Above 8

What environments do alkaliphiles thrive in?

Alkaline environments

What are exoenzymes?

Enzymes secreted outside the cell

Why are exoenzymes needed?

To break down large molecules that cannot enter the cell

What process do exoenzymes use to break bonds?

Hydrolysis

What does hydrolysis do?

Breaks bonds by adding water

What is produced after hydrolysis?

Smaller molecules that can be absorbed

Which enzyme is associated with starch agar?

Amylase

Which enzyme is associated with tributyrin agar?

Lipase

Which enzyme is associated with milk agar?

Caseinase or protease

Which enzyme is associated with gelatin deep?

Gelatinase

Which enzyme is associated with DNA agar?

DNase

What does SIM agar stand for?

Sulfide, Indole, Motility

What type of media is SIM agar?

Semi-solid deep

How many tests does SIM agar perform?

Three

What indicates a positive sulfur test in SIM?

Black precipitate

What gas causes black precipitate in SIM?

H2S

What enzymes produce H2S?

Cysteine desulfurase or thiosulfate reductase

What reacts with H2S to form black precipitate?

Fe2+

What compound is formed in SIM sulfur test?

Ferrous sulfide (FeS)

What indicates a positive indole test?

Cherry-red ring at top after Kovac’s reagent

What enzyme produces indole?

Tryptophanase

What does tryptophanase break down?

Tryptophan

What are products of tryptophan breakdown?

Indole, pyruvic acid, ammonia

What reagent detects indole?

Kovac’s reagent

What indicates motility in SIM?

Growth spreading from stab line

Why can motile bacteria spread in SIM?

Semi-solid agar allows movement

What does cloudy growth away from stab indicate?

Motility

What does MR test detect?

High amounts of organic acids

What reagent is used in MR test?

Methyl red indicator

What color is a positive MR test?

Red

What does a positive MR test mean?

Strong acid fermentation

What does VP test detect?

Neutral end products (acetoin, 2,3-butanediol)

What reagents are used in VP test?

Barritt’s A and B

What color is a positive VP test?

Brownish-red

What type of broth is used for MR and VP tests?

MR-VP broth

Why are MR and VP tests paired?

They detect opposite products

What result is E. coli for MR and VP?

MR+ VP-

What result is Enterobacter for MR and VP?

MR- VP+

What does the citrate test determine?

If organism can use citrate as only carbon source

What media is used in citrate test?

Simmons citrate agar

What is the only carbon source in citrate test?

Citrate

What is the only nitrogen source in citrate test?

Ammonium salts

What enzyme is used in citrate test?

Citrate permease

What happens when citrate is metabolized?

Produces alkaline products

What happens to pH in positive citrate test?

Increases

What indicator is used in citrate test?

Bromothymol blue

What color is a negative citrate test?

Green

What color is a positive citrate test?

Blue

What does urease break down?

Urea

What does urease produce?

Ammonia (NH3)

What happens to pH in urease test?

Increases

What color indicates positive urease test?

Pink/fuchsia

What organisms are urease positive?

Klebsiella pneumoniae and Proteus

What organisms are urease negative?

E. coli and Salmonella

What does tryptophanase produce?

Indole

What indicator detects indole?

Kovac’s reagent

What does decarboxylase remove?

COO- group

What does decarboxylase produce?

NH3 or CO2

What indicator detects NH3 from decarboxylase?

Phenol red

What indicator detects CO2 from decarboxylase?

Bromocresol purple

What does phenylalanine deaminase remove?

NH2 group

What does phenylalanine deaminase produce?

Phenylpyruvic acid

What indicator detects phenylpyruvic acid?

FeCl3

What is produced from lysine degradation?

Cadaverine or putrescine