Bacterial Physiology Lab: IMViC, KIA & Oxygen Tests

What is the purpose of the IMViC tests?

To identify gram-negative rods, particularly members of the Enterobacteriaceae family.

What does the methyl red test indicate?

It tests for mixed acid fermentation.

What does the Voges-Proskauer test detect?

The presence of the 2,3-butanediol pathway.

What is the significance of the citrate test?

It tests for the production of citrate permease.

What does the indole test measure?

The presence of tryptophanase by detecting indole production.

What does Kligler's Iron Agar (KIA) test for?

Carbohydrate utilization, including lactose and glucose, hydrogen sulfide production, and gas production.

What are the growth patterns in thioglycollate medium?

They indicate different types of oxygen utilization/aerotolerance.

What does a positive catalase test indicate?

The bacterium can produce the enzyme catalase, which breaks down hydrogen peroxide.

What are obligate aerobes?

Bacteria that require oxygen for growth.

What are obligate anaerobes?

Bacteria that cannot grow in the presence of oxygen.

What is a facultative anaerobe?

Bacteria that can grow with or without oxygen.

What are microaerophiles?

Bacteria that require low levels of oxygen for growth.

What does the term 'aerotolerant anaerobe' mean?

Bacteria that can tolerate oxygen but do not use it for growth.

What is the role of tryptophanase?

It hydrolyzes tryptophan into indole, pyruvic acid, and ammonia.

What does a positive result in the indole test look like?

The formation of a red ring after adding Kovac's reagent.

What does a positive methyl red test indicate?

The presence of stable acids from glucose fermentation.

What is the purpose of the Voges-Proskauer test?

To detect acetoin as an intermediate in 2,3-butanediol fermentation.

What does a positive citrate test indicate?

The bacterium can utilize citrate as its sole carbon source.

What does Kligler's Iron Agar test for?

Lactose and glucose fermentation, hydrogen sulfide production, and gas production.

What is the significance of the catalase test?

It differentiates species based on their ability to produce catalase.

What does a negative catalase test indicate?

The bacterium does not produce catalase and cannot break down hydrogen peroxide.

What is the primary indicator species for fecal contamination?

Escherichia coli (E. coli).

What does the term 'reducing media' refer to?

Media that contains components that remove oxygen to support anaerobic growth.

What is the function of fluid thioglycollate medium?

It supports the growth of both aerobic and anaerobic bacteria.

What does the presence of hydrogen peroxide indicate?

It is a byproduct of aerobic respiration that can be toxic to cells.

What reagent is added to detect indole?

Kovac's reagent (composed of 4-dimethylaminobenzaldehyde, butanol, and hydrochloric acid)

What indicates a positive reaction for indole detection?

Formation of a cherry red color

What color indicates a positive Voges-Proskauer test?

Rose color after the addition of VP reagents A and B

What does a yellow slant and yellow butt indicate in KIA?

The organism can ferment both glucose and lactose

What does a red slant and yellow butt indicate in KIA?

The organism can only ferment glucose

What does the presence of a black precipitate in KIA indicate?

The organism produces hydrogen sulfide (H2S) and has fermented carbohydrates

What is the role of phenol red in KIA?

It serves as a pH indicator

What does the term 'reversion' refer to in KIA?

The process where the aerobic region of the slant raises the pH after glucose is depleted

What does a red slant indicate in the KIA experiment?

Glucose fermentation.

What does a yellow slant indicate in the KIA experiment?

Glucose and lactose fermentation.

What is the significance of gas bubbles or cracks *********** of the KIA tube?

They indicate gas production from carbohydrate fermentation.

What is the critical timing for reading KIA results?

Results should be analyzed as close to 24 hours after inoculation as possible.

What is aerobic respiration?

The process by which organisms convert biochemical energy into ATP using oxygen as the final electron acceptor.

How do facultative anaerobes differ from obligate aerobes?

Facultative anaerobes can use oxygen but can also switch to fermentation or anaerobic respiration when oxygen is absent.

What are aerotolerant anaerobes?

Organisms that undergo fermentation and do not use oxygen but can survive in oxygen-rich environments.

What defines obligate anaerobes?

Bacteria that cannot tolerate oxygen and obtain energy from anaerobic respiration or fermentation.

What is the role of sodium thioglycollate in fluid thioglycollate medium?

It reduces the oxidation-reduction potential of the medium, binding free oxygen.