Microbiology Laboratory Midterm Review Flashcards

60 vocabulary flashcards covering microbiology laboratory concepts, safety procedures, equipment, media, bacterial techniques, organisms, and staining protocols.

Antiseptic

A chemical antimicrobial agent designed for use on living tissue (such as skin and mucous membranes); examples include alcohol wipes and iodine/Betadine.

Disinfectant

A chemical agent used on non-living surfaces and equipment (such as laboratory benches); examples include bleach solution and Lysol.

Autoclave

A device that sterilizes biohazardous waste using steam under pressure prior to hazardous-material pickup.

Sharps Container

A puncture-resistant container used exclusively for disposing of sharp biohazardous objects such as needles, razor blades, and glass slides.

Aseptic Technique

A set of procedures designed to prevent contamination of cultures, the lab environment, and personnel (e.g., flaming inoculating loops, working near a flame, keeping lids on plates).

Colony

A visible mass of bacterial cells (consisting of millions of cells) arising from a single cell or colony-forming unit (CFU) on solid medium.

HAIs (Healthcare-Associated Infections)

Infections acquired by patients while receiving treatment in a healthcare facility that were neither present nor incubating upon admission (e.g., MRSA, C. difficile).

Inoculating Loop

A lab tool with a wire loop end used to transfer bacterial cultures to broths, slants, and plates; flamed to red-hot before and after each use.

Inoculating Needle

A tool with a straight wire end used specifically to stab agar deeps.

Bunsen Burner

A heat source used to sterilize loops and needles, heat-fix slides, and create an upward thermal convection current that reduces airborne contamination.

Petri Dish

A two-part container (base and lid) holding solid agar media used for bacterial isolation and lawns.

Culture Tubes

Glass or plastic tubes used to hold liquid broth, agar slants, or agar deeps, kept with caps loosely on to permit gas exchange.

Inverted Incubation

Incubating Petri dishes agar-side up so that moisture condensation forms on the lid instead of dripping onto the agar surface and smearing colonies.

Trypticase Soy Agar (TSA)

A general-purpose nutritional medium that supports the growth of a wide variety of non-fastidious bacteria.

Fishtail Inoculation

A zig-zag inoculation technique using an inoculating loop along the surface of an agar slant to produce heavy growth across a large surface area.

Dip and Swirl Inoculation

A method using an inoculating loop to disperse bacterial cells evenly throughout a liquid broth medium.

Stab Inoculation

A technique performed with an inoculating needle pushed straight down the center of an agar deep tube and withdrawn along the same path to test aerotolerance.

Quadrant Streak

An isolation technique in which a culture is sequentially diluted across four quadrants on an agar plate with flaming between quadrants to obtain isolated single colonies.

Bacterial Lawn

A uniform layer of continuous bacterial growth covering an entire agar plate, prepared by swabbing the plate in three directions (rotating $60^\text{o}$ each time).

Necator americanus

A multicellular eukaryotic helminth (hookworm) with a tubular body and buccal capsule containing cutting plates used to attach to the host's intestinal wall.

Rhizopus sp.

A microscopic fungus (black bread mold) characterized by sporangia, sporangiophores, hyphae, rhizoids, and stolons.

Trypanosoma brucei

A flagellated protozoan parasite causing African sleeping sickness, recognized as slender, curved cells among red blood cells with a flagellum, undulating membrane, nucleus, and kinetoplast.

Borrelia burgdorferi

A thin, loosely coiled spiral-shaped spirochete bacterium that causes Lyme disease and is transmitted by Ixodes (deer) ticks.

Eukaryotic Cell

A cell type featuring a membrane-bound nucleus and membrane-bound organelles, typically larger in size ($20\text{--}50\text{ }\frac{1}{\text{m}}$ in human cheek cells).

Prokaryotic Cell

A smaller cell type ($1\text{--}5\text{ }\frac{1}{\text{m}}$) lacking a true membrane-bound nucleus, containing its DNA free in a nucleoid region.

Turbid

A broth growth description indicating uniform cloudiness throughout the liquid due to suspended bacterial cells (e.g., E. coli).

Flocculent

A pattern of growth in broth culture characterized by visible clumps or floating flakes of bacteria distributed in the liquid.

Pellicle

A surface film or skin of bacterial growth at the top of liquid broth, formed by organisms requiring high oxygen levels (e.g., Pseudomonas aeruginosa).

Sediment

A pattern of bacterial growth in liquid broth where cells settle and accumulate at the bottom of the tube.

Obligate Aerobe

An organism requiring $O_2$ for aerobic respiration, showing growth only at the top surface of an agar deep tube (e.g., Pseudomonas aeruginosa).

Facultative Anaerobe

An organism that uses $O_2$ when present but can ferment or grow anaerobically without it, displaying growth all along the stab line in an agar deep (e.g., E. coli, S. aureus).

Obligate Anaerobe

An organism for which $O_2$ is toxic, displaying growth only at the bottom of an agar deep tube where oxygen concentrations are lowest (e.g., Clostridium sporogenes).

Iris Diaphragm

A component of a compound light microscope situated beneath the stage that regulates the amount of light reaching the slide to adjust contrast.

Interpupillary Distance Adjustment

A microscope control that changes the spacing between ocular lenses to align with the observer's eyes, reducing strain and unifying the field of view.

Total Magnification

The calculated total power of magnification produced by multiplying the ocular lens magnification ($10\times$) by the objective lens magnification.

Oil Immersion

Microscopic technique using immersion oil with the $100\times$ objective lens ($1000\times$ total magnification) to prevent light refraction; adjusted only with fine focus.

Basic Stain

A dye carrying a positive charge that is electrostatically attracted to the negative bacterial surface, resulting in direct staining of the cell (e.g., crystal violet, safranin).

Acidic Stain

A dye carrying a negative charge that is repelled by the negative cell surface, leaving the bacterial cell colorless against a stained background (e.g., nigrosin, India ink).

Smear Preparation

The step-by-step procedure of spreading bacteria thinly on a slide, allowing it to completely air-dry, and heat-fixing it prior to staining.

Heat Fixing

Passing an air-dried bacterial smear through a Bunsen burner flame 2–3 times to melt lipids, adhere cells to the slide, kill pathogens, and preserve morphology.

Negative Stain

A simple staining technique using an acidic dye (nigrosin) without heat fixing, used to view delicate cells or un-distorted morphology against a dark background.

Gram Stain

A differential stain that differentiates bacterial cells into Gram-positive (purple) or Gram-negative (pink/red) based on structural differences in their cell envelope.

Crystal Violet

The primary stain in the Gram stain procedure applied for approximately 1 minute, coloring all bacterial cells purple.

Gram's Iodine

The mordant in the Gram stain procedure applied for approximately 1 minute to form an insoluble crystal violet-iodine complex inside the peptidoglycan wall.

Decolorizer (Alcohol/Acetone)

The critical step in Gram staining (applied for 10–20 seconds) that strips the crystal violet complex from Gram-negative cells while retaining it in thick Gram-positive cell walls.

Safranin

The counterstain in the Gram stain (and endospore stain) applied for 1 minute to stain decolorized Gram-negative cells pink/red.

Gram-Positive Cell Wall

A cell envelope structure characterized by a thick peptidoglycan layer and no outer membrane, retaining the crystal violet dye to appear purple.

Gram-Negative Cell Wall

A cell envelope featuring a thin peptidoglycan layer and an outer lipopolysaccharide (LPS) membrane, which loses primary stain during decolorization and stains pink/red.

Acid-Fast Stain

A differential stain using heated carbol fuchsin to penetrate waxy mycolic acid in Mycobacterium cell walls; acid-fast cells appear red/pink and non-acid-fast cells appear blue.

Capsule Stain

A differential staining method using acidic and basic dyes without heat fixing to reveal non-ionic bacterial capsules as clear halos surrounding stained cells.

Endospore Stain

A differential stain employing heat/steam to drive malachite green into resistant endospores, followed by safranin counterstain (spores appear green, vegetative cells appear pink).

Monotrichous

A bacterial flagellar arrangement characterized by a single flagellum attached at one pole of the cell.

Lophotrichous

A flagellar arrangement featuring a tuft or cluster of multiple flagella emerging from a single pole of the bacterial cell.

Amphitrichous

A flagellar arrangement where single or multiple flagella extend from both opposite poles of the bacterial cell.

Peritrichous

A bacterial flagellar arrangement in which flagella project in all directions from all over the cell surface (e.g., E. coli).

Mycolic Acid

A waxy cell-wall lipid found in Mycobacterium species that enhances virulence by allowing bacteria to survive within host macrophages and resist phagocytic killing.

Capsule

A slippery polysaccharide layer outer coating on certain bacteria that prevents phagocytosis by host white blood cells.

Endospores

Dormant, extremely resistant bacterial structures produced under harsh conditions that promote survival against heat, drying, and disinfectants.

Bacillus megaterium

A large, aerobic, Gram-positive rod-shaped bacterium capable of forming endospores, frequently arranged in chains.

Serratia marcescens

A Gram-negative, facultatively anaerobic rod-shaped bacterium that produces a red/pink pigment called prodigiosin when grown at room temperature.