Microbiology Lab Midterm Review Flashcards

Vocabulary flashcards covering microbiology laboratory concepts including staining methods, microscopy, culture media, biochemical tests, bacterial structures, and antibiotic susceptibility.

Coccus

A round or spherical bacterium.

Bacillus

A rod-shaped bacterium.

Staphylo-

Cellular arrangement where cells are organized in clusters.

Strepto-

Cellular arrangement where cells are organized in chains.

Gram-positive bacteria

Bacteria that stain purple in the Gram staining procedure.

Gram-negative bacteria

Bacteria that stain pink or red in the Gram staining procedure.

Crystal violet

The primary stain in the Gram staining procedure.

Gram's iodine

The mordant reagent in the Gram staining procedure.

Decolorizer (Gram stain)

Reagent that removes crystal violet-iodine complexes from Gram-negative cells.

Safranin

The counterstain in the Gram staining procedure.

Over-decolorization

Staining error that may cause Gram-positive cells to appear Gram-negative.

Total magnification ($100\text{X}$ objective)

$1000\text{X}$ total magnification when combined with a $10\text{X}$ ocular lens.

Field diameter ($1000\text{X}$)

$0.2\,\text{mm}$ or $200\,\mu\text{m}$ at $1000\text{X}$ total magnification per the practice sheet.

Cell size estimation formula

Field diameter divided by the number of cells fitting across.

Immersion oil

Substance that reduces refraction and improves resolution at $1000\text{X}$ total magnification.

Inverted incubation

Incubating agar plates upside down with the agar side positioned up.

Streak isolation

A method to dilute bacteria across agar to obtain isolated colonies (at least $8$ isolated colonies required in the review).

BSL-2

Biosafety Level 2, which is more restrictive than BSL-1.

Bacterial genus and species format

Capitalize genus, lowercase species, and either italicize or underline both.

Supportive medium

A nutrient-rich growth medium that supports many organisms.

Selective medium

A growth medium that inhibits some organisms while allowing others to grow.

Differential medium

A growth medium that distinguishes microbes through visible reactions.

TSA-Blood agar

A supportive and differential medium (not selective) made differential by whole red blood cells.

Alpha hemolysis

Partial hemolysis resulting in a greenish discoloration on blood agar.

Beta hemolysis

Complete lysis of red blood cells producing a clear zone on blood agar; causes the greatest RBC destruction.

Gamma hemolysis

No hemolysis, resulting in unchanged agar.

Hemolysins

Substances that damage or lyse red blood cells, acting as virulence factors that indicate potential pathogenicity.

CNA-Blood agar

A selective and differential medium containing colistin and nalidixic acid to select for Gram-positive bacteria, and whole red blood cells for differentiation.

MacConkey agar

A selective and differential medium containing bile salts and crystal violet to select for Gram-negative bacteria, neutral red as a pH indicator, and lactose as the test carbohydrate.

Coliform

A Gram-negative bacterium that ferments lactose with acid and gas.

Chocolate agar

An enriched supportive medium containing lysed blood cells that supports fastidious organisms requiring growth factors; cannot test for hemolysis.

Candle jar

An incubation chamber that increases $CO_2$ and somewhat decreases $O_2$.

Catalase

An enzyme that breaks hydrogen peroxide into water and oxygen ($2 H_2O_2 \rightarrow 2 H_2O + O_2$), indicated by immediate bubbles upon adding hydrogen peroxide.

Oxidase test

A test detecting cytochrome c oxidase activity, where a positive result produces a rapid dark purple color after adding reagent.

Obligate aerobe

An organism that requires oxygen to grow.

Obligate anaerobe

An organism that cannot grow in the presence of oxygen.

Facultative anaerobe

An organism that grows with or without oxygen.

Aerotolerant anaerobe

An organism that tolerates oxygen but does not use it for respiration.

Microaerophile

An organism that requires oxygen below atmospheric levels.

Durham tube

A small inverted tube used to detect gas produced during carbohydrate fermentation.

Triple Sugar Iron (TSI) agar

A differential medium containing glucose, lactose, and sucrose, where yellow indicates acid, red indicates alkaline, black indicates $H_2S$, and cracking or lifting indicates gas.

TSI K/A

Alkaline slant and acid butt reaction in TSI indicating glucose fermentation only.

TSI A/A

Acid slant and acid butt reaction in TSI indicating fermentation of glucose plus lactose and/or sucrose.

Methyl red (MR) test

A test that detects stable acid from mixed-acid glucose fermentation; positive results turn red after reagent addition.

Voges-Proskauer (VP) test

A test that detects acetoin from 2,3-butanediol fermentation; positive results turn red after adding VP reagents and developing.

Urease test

A test detecting urea breakdown into ammonia, raising the pH to produce a bright pink color; suggests pathogenic potential in the stomach or urinary tract.

Lysine decarboxylase

An enzyme that removes the carboxyl group from lysine to produce cadaverine.

Phenylalanine deaminase

An enzyme that removes the amino group from phenylalanine; yields a green color after ferric chloride reagent is added.

SIM medium

A multi-test medium that evaluates Sulfide production (blackening), Indole production (red ring with Kovac's reagent), and Motility (diffuse growth from stab line).

Tryptophanase

An enzyme that converts tryptophan into indole.

Monotrichous

Having a single flagellum located at one pole.

Lophotrichous

Having a tuft of flagella located at one pole.

Amphitrichous

Having flagella located at both poles.

Peritrichous

Having flagella distributed uniformly around the cell.

Endospore

A specialized bacterial structure whose function is survival in harsh conditions.

Capsule

A bacterial outer structure whose function is protection against phagocytosis and drying.

Inclusion bodies

Intracellular bacterial structures used for nutrient or reserve storage.

Acid-fast genera

Mycobacterium (acid-fast positive) and some Nocardia (partially acid-fast).

Coagulase

An enzyme that promotes plasma clotting through fibrin formation; used to identify Staphylococcus aureus via clot formation in plasma.

Zone of inhibition

A clear zone around an antibiotic disc where microbial growth is inhibited, measured by full diameter in millimeters ($\text{mm}$).

Antibiotic disc NB

Novobiocin disc; a zone diameter greater than $16\,\text{mm}$ indicates sensitivity per the review sheet.

Antibiotic disc P

Optochin disc, according to the review sheet.

Antibiotic disc A

Bacitracin disc in the lab antibiotic test.