York College - CUNY Bio 265L Lab Notes on Gram Negative Bacteria

Flashcards covering key concepts and biochemical tests related to the Enterobacteriaceae family and Gram-negative bacteria as discussed in the lab session.

Enterobacteriaceae

A family of bacteria that includes many gram-negative species commonly found in the intestines.

Gram stain reaction

A method to differentiate bacterial species into gram-positive and gram-negative based on cell wall composition.

Catalase test

A biochemical test that determines the presence of the enzyme catalase in bacteria, which breaks down hydrogen peroxide.

Oxidase test

A biochemical test that checks for the presence of cytochrome c oxidase in bacteria by identifying a color change.

TSI

Triple Sugar Iron agar test used to differentiate enteric gram-negative bacteria based on sugar fermentation and hydrogen sulfide production.

IMViC tests

A series of four biochemical tests (Indole, Methyl Red, Voges-Proskauer, Citrate) used to differentiate members of the Enterobacteriaceae family.

Nitrate reduction test

A test to determine the ability of bacteria to reduce nitrates to nitrites or further to nitrogen gas.

Kovac's reagent

A reagent used in the indole production test that turns pink in positive results.

Methyl red

A pH indicator used in the mixed acid fermentation test that turns red in acidic conditions.

Barritt's solution A/B

Reagents used in the Voges-Proskauer test that show a red-brown color for positive results.

Positive control

A known substance or organism used to ensure that a test works correctly, such as Pseudomonas fluorescens for the oxidase test.