Microbiology Lecture Flashcards

Vocabulary flashcards for microbiology lecture notes.

Hemolysis

Breakdown (lysis) of red blood cells (RBCs) via enzymes called hemolysins.

Blood Agar

A TSA-like medium that is red due to 5% sheep blood, used to determine if bacteria can lyse RBCs (perform hemolysis).

Beta Hemolysis (β)

Complete hemolysis with RBCs fully lysed, resulting in a transparent/clear zone around the colony.

Alpha Hemolysis (α)

Partial hemolysis with RBCs partially degraded, resulting in a greenish or dark halo around colonies.

Gamma Hemolysis (γ)

No hemolysis, no RBC breakdown, with the medium remaining unchanged red around colonies (negative result).

Mannitol Salt Agar

A selective and differential medium containing mannitol, 5% salt, and phenol red (pH indicator) used to differentiate organisms based on mannitol fermentation.

DNAse Agar

A differential medium that tests for the ability of an organism to degrade deoxyribonucleic acid (DNA) with the enzyme DNAse.

Salt Broth

Nutrient broth with 6.5% NaCl, used as a selective medium to determine if organisms can grow in high salt concentrations.

Bile Esculin Slant

A selective and differential medium containing bile (inhibits some organisms), esculin (sugar alcohol), and ferric citrate (iron source); black color indicates esculin breakdown.

Micrococcaceae

Includes the genera Staphylococcus and Micrococcus; Gram-positive cocci in clusters or tetrads, always catalase positive.

Streptococcaceae

Includes the genera Streptococcus, Enterococcus, and Lactococcus; Gram-positive cocci in chains or pairs, always catalase negative.

Neisseriaceae

Includes the genera Neisseria, Branhamella, and Moraxella; Gram-negative diplococci, always catalase positive and are Capnophiles.

Corynebacterium

Gram-positive short rods that are catalase positive and display irregular branching of cells (Palisades structures, ‘Chinese letters’).

Fermentation of Carbohydrates

Tests for utilization of a carbohydrate as a carbon and energy source, resulting in acid end products and a color change of phenol red from red to yellow.

O/F Glucose Test

Tests for aerobic respiration (O tube) and fermentation (F tube, sealed with mineral oil) to determine glucose metabolism pathways.

Nitrate Test

Tests for the utilization of nitrate (NO3-) as a terminal electron acceptor in anaerobic respiration.

Oxidase Test

Tests for cytochrome oxidase activity; a positive result is indicated by a color change to purple within 15 seconds.

Citrate Test

Tests for the ability of organisms to utilize citric acid as the sole carbon and energy source, resulting in an alkaline pH and a color change from green to blue.

Methyl Red Test

Tests for mixed acid fermentation, resulting in a pH below 4.4 and a broth color change to red.

Voges-Proskauer Test

Tests for 2,3-Butanediol fermentation; a positive result is indicated by a brownish-red broth after adding α-naphthol and KOH.

Starch Hydrolysis

Tests for the presence of amylase, which degrades starch, resulting in a clearing around the growth after adding iodine.

Casein Hydrolysis

Tests for caseinase, which degrades casein (milk protein), resulting in a clearing around the growth on milk agar.

Lipid Hydrolysis

Tests for the presence of lipase, which degrades fats, resulting in a dark blue line of dye around the growth on Spirit Blue Agar.

Urea Broth

Tests for the presence of urease, which breaks down urea into ammonia and CO2, resulting in an alkaline pH and a color change to fuschia.

Triple Sugar Iron (TSI)

Differential test that assesses carbohydrate fermentation (glucose, lactose, sucrose) and H2S production.

Sulfide Indole Motility (SIM)

Combined test that assesses sulfide production, indole production, and motility.

Phenylalanine Slant

Tests for phenylalanine deaminase, which results in phenylpyruvic acid production; detected by adding 10% FeCl3.

Eosin Methylene Blue (EMB)

Selective and differential medium containing lactose and sucrose: lactose fermentors will be pink or metallic green.

MacConkey Agar (MAC)

Selective and differential medium containing lactose, bile salts, and crystal violet; lactose fermentors will be pink, vigorous fermentors will have a bile precipitate.

Salmonella-Shigella Agar (SS)

Selective and differential medium containing lactose and bile salts; lactose fermentors will be pink, and sulfur reducers will form black colonies.

Decarboxylase Test

Tests for an enzyme to decarboxylate a particular amino acid active at acidic pH; The pH must become acidic from glucose fermentation for the enzymes to be turned on