Biochemical Tests: Fermentation and Respiration Methods

Biochemical tests

Assess metabolic capabilities of microorganisms.

Pure cultures

Isolated microbial populations for accurate testing.

Aseptic technique

Prevents contamination during microbial handling.

Sharpie marker

Used for labeling test tubes and plates.

O-F test

Determines glucose metabolism under different oxygen conditions.

Phenol red

pH indicator used in sugar broth tests.

Methyl Red Test

Tests for mixed acid fermentation by bacteria.

Incubation time

Duration cultures are kept under specific conditions.

Positive result

Indicates successful metabolic activity in tests.

Negative result

Indicates lack of metabolic activity in tests.

Durham tube

Collects gas produced during fermentation tests.

Reversion

False negative due to prolonged incubation.

Bromthymol blue

pH indicator used in O-F test.

Glucose

Fermentable sugar used in various tests.

Peptone

Protein source in Methyl Red Test media.

Buffer

Maintains stable pH during fermentation tests.

Gas production

Indicates fermentation activity in sugar tests.

Acid production

Byproduct of fermentation, indicated by color change.

Test media

Nutrient-rich environment for microbial growth.

Atlas photos

Visual reference for comparing test results.

Lab handouts

Guidelines for conducting biochemical tests.

Respiration

Biochemical pathways producing ATP in organisms.

Electron Acceptors

Molecules used by species during respiration.

Catalase Test

Tests for catalase enzyme using hydrogen peroxide.

Oxidase Test

Detects cytochrome c oxidase with ninhydrin reagent.

Nitrate Test

Determines if bacteria use nitrate as electron acceptor.

Nitrite Presence Test

Uses sulfanilic acid and dimethyl-alpha-naphthylamine.

Nitrate Presence Test

Involves zinc to check for nitrate reduction.

Simmon's Citrate Test

Tests if bacteria can use citrate as carbon source.

Decarboxylation Test

Tests bacteria's ability to metabolize amino acids.

Phenylalanine Deaminase Test

Detects phenylalanine deaminase in bacteria.

Hydrogen Peroxide

Reactive oxygen species used in catalase test.

Bromthymol Blue

pH indicator for Simmon's citrate test.

Bromcresol Purple

pH indicator for decarboxylation test.

Royal Blue Media

Positive result for citrate utilization test.

Green Media

Negative result for citrate utilization test.

Purple Media

Positive result for decarboxylation test.

Yellow Media

Negative result for decarboxylation test.

Incubation Time

48 hours for nitrate and citrate tests.

Incubation Time

3-4 days for decarboxylation test.

Zinc Powder

Used to confirm nitrate presence in nitrate test.

Reactive Oxygen Species (ROS)

Harmful byproducts that catalase protects against.

Ferric Chloride Test

Detects phenylpyruvate presence in bacteria.

Positive Result

Greengreen color indicates phenylalanine metabolism.

Negative Result

Yellowyellow color shows no phenylalanine metabolism.

Indole Test

Tests tryptophan utilization by bacteria.

Kovac's Reagent

Reacts with indole to show positive result.

Positive Indole Result

Red ring at top indicates tryptophan metabolism.

Negative Indole Result

Absence of red ring indicates no tryptophan metabolism.

Bile Esculin Test

Tests growth in bile presence and esculin hydrolysis.

Selective Agent

Bile salts inhibit Gram-positive bacteria growth.

Differential Ingredient

Esculin and ferric citrate used for identification.

Positive Bile Esculin Result

Black-brown media indicates esculin hydrolysis.

Negative Bile Esculin Result

Dark gold media shows no esculin hydrolysis.

Starch Hydrolysis Test

Determines bacteria's ability to hydrolyze starch.

Amylase

Enzyme that hydrolyzes starch into simple sugars.

Positive Starch Result

Clear halo around growth indicates starch hydrolysis.

Negative Starch Result

Lack of clear halo shows no starch hydrolysis.

Urea Hydrolysis Test

Tests urea hydrolysis by bacteria.

Phenol Red

Indicator for pH change in urea hydrolysis.

Positive Urea Result

Fuchsia pink color indicates urea hydrolysis.

Negative Urea Result

No color change indicates no urea hydrolysis.

ONPG Test

Tests for β-galactosidase enzyme production.

Bright Yellow Result

Indicates positive ONPG test for lactose metabolism.

Casein Hydrolysis Test

Determines ability to hydrolyze milk protein casein.

Caseinase

Enzyme that hydrolyzes casein in milk.

Gelatin Hydrolysis Test

Tests for gelatinase production by bacteria.

Liquefied Media Result

Indicates positive gelatin hydrolysis after cooling.

KIA Test

Combines tests for glucose, lactose, gas, and H2S.

Phenol Red Indicator

Shows pH change during fermentation in KIA.