Laboratory Exercises on Nitrogen Metabolism and Bacterial Tests lab 10

This set of flashcards covers key concepts in nitrogen metabolism, bacterial classification, and specific laboratory tests relevant to microbiology.

Nitrogen Cycle

The series of processes by which nitrogen and its compounds are interconverted in the environment and in living organisms.

Ammonia

A compound of nitrogen and hydrogen (NH3), produced during the breakdown of organic matter.

Nitrate

A nitrogen compound that is less toxic than ammonia, used by plants as a nutrient.

Nitrite

A product formed from the breakdown of ammonia, which is also toxic but less so than ammonia itself.

Bile Esculin Agar (BEA) Test

A selective and differential agar used to isolate and identify Enterococcus by hydrolyzing esculin.

Lancefield Classification

A system to distinguish between different strains of beta-hemolytic streptococci based on polysaccharide antigens.

Enterococcus

A genus of bacteria that are part of the normal gut flora but can be opportunistic pathogens.

Peptides

Chains of amino acids connected by peptide bonds, typically smaller than proteins.

Cysteine

An amino acid containing sulfur that can be metabolized by certain bacteria to produce hydrogen sulfide.

Hydrogen Sulfide Production

A byproduct of the metabolism of sulfur-containing compounds by certain bacteria.

Indole Production

The process of converting tryptophan into indole, detectable by adding Kovac's reagent.

Motility Reaction

The ability of certain bacteria to move away from their point of origin in the SIM media.

Urease Test

A test that detects the enzyme urease, indicating the ability of certain bacteria to hydrolyze urea into ammonia. This process results in an increase in pH, which changes the color of the medium to pink.

Positive BEA Test

Indicates the ability of bacteria to hydrolyze esculin in the presence of bile salts, resulting in a dark precipitate.

Negative BEA Test

Indicates that bacteria cannot hydrolyze esculin in the presence of bile salts, resulting in no color change.

Assimilatory

Making precursors for amino acids and other compounds from inorganic nitrogen sources.

Dissimilatory

Make ATP by converting inorganic nitrogen into ammonia or nitrogen gas, often through denitrification.

SIM Agar

A selective medium used for the determination of hydrogen sulfide production, indole formation, and motility of bacteria.

SIM Sulfur Reaction

SIM agar result is cystenine disulferase is present: Black color in tube

SIM Indole reaction

The presence of indole is indicated by a red ring after adding Kovac's reagent, suggesting the ability of bacteria to convert tryptophan into indole. Positive= cherry red color.

SIM Motility Reaction

Indicates the ability of bacteria to move, resulting in a diffuse growth away from the stab line in the medium, suggesting motility.

API 20 E Test

A biochemical test used to identify Enterobacteriaceae and other non-fermentative Gram-negative bacteria through various substrate reactions.