BIO205: Lab Final

Ocular Lens

The lens you look through, typically magnifying the image 10 times.

Objective Lenses

Lenses on the rotating nosepiece providing primary magnification, usually 4x, 10x, 40x, and 100x oil immersion.

Coarse Adjustment Knob

Moves the stage rapidly up and down for initial focusing (use only with low-power objectives).

Fine Adjustment Knob

Allows precise, slight stage movements for sharp focusing under high power.

Condenser

Focuses and concentrates light from the illuminator onto the specimen.

Iris Diaphragm

Regulates the amount of light passing through the condenser to adjust contrast and resolution.

Total Magnification

Total magnification = Magnification of ocular lens x Magnification of objective lens.

Iris Diaphragm

Controls the amount of light reaching the oculars.

Simple Stain

Uses a single basic dye; all cells appear the same color against a bright background.

Negative Stain

Cells remain clear/uncolored while the background is darkened by an acidic dye.

Differential Stain

Uses multiple dyes to distinguish between different types of bacteria or structures.

Heat Fixing

Accomplishes killing bacteria, adhesion of bacteria to the slide, and preserving cell shape.

Simple Stains Charge

Positively charged (cationic) dyes that bind to the negatively charged bacterial cell wall.

Negative Stains Charge

Negatively charged (anionic) dyes that stain only the background.

Primary Stain

Crystal Violet stains all bacterial cell walls purple.

Mordant

Gram's Iodine forms a large water-insoluble crystal violet-iodine complex inside the cell.

Decolorizer

95% Ethanol/Acetone washes out the dye complex from Gram-negative cells.

Counterstain

Safranin stains the decolorized Gram-negative cells pink/red.

Gram-Positive

Cells that appear purple after Gram staining.

Gram-Negative

Cells that appear pink/red after Gram staining.

Mycobacterium

A genus identified using the acid-fast stain, known for causing Tuberculosis.

Nocardia

A genus identified using the acid-fast stain, distinct from Mycobacterium.

Acid-Fast Disease

Diseases caused by acid-fast bacteria include Tuberculosis, Leprosy, and Nocardiosis.

Acid-Fast Organisms

Appear bright pink/red due to carbolfuchsin retention.

Non-Acid-Fast Organisms

Stain blue due to methylene blue counterstain.

Gram Stain

Separates bacteria based on cell wall structure (peptidoglycan thickness).

Acid-Fast Stain

Separates bacteria based on presence of mycolic acid in cell walls.

Microbiota

Types of microorganisms that reside on our bodies.

Alcohol-Based Sanitizer Concerns

Over-reliance can cause skin irritation and fails to eliminate some resilient microbes.

Clamshell Technique

Technique to minimize contamination while accessing the agar surface.

Serial Dilutions Purpose

To reduce dense bacterial concentrations to a countable range.

Countable Plate Range

A plate must have between 30 and 300 colonies to be statistically valid.

Titer CFU/mL Calculation

Titer (CFU/mL) = Number of Colonies (CFU) / (Volume Inoculated (mL) x Plate Dilution Factor).

Fungi

Eukaryotes with a true nucleus and membrane-bound organelles.

Mold Structure

Composed of multicellular filaments called hyphae.

Reproduction of Mold

Occurs by forming asexual or sexual spores.

Disinfectant

Chemical agent applied to non-living surfaces to destroy or inhibit microbes.

Antiseptic

Milder chemical agent safe enough for living tissues.

Sanitization

Lowers microbial counts to safe levels without necessarily killing all microbes.

Disinfection

Actively kills pathogenic microbes on surfaces.

Resistance Features

Structures like cell walls and endospores that increase resistance to disinfectants.

DNA Solubility in Water

DNA is soluble in water due to its polar phosphate backbone.

DNA Solubility in Alcohol

DNA is insoluble in alcohol, causing precipitation.

Aseptic Transfer

Sterile movement of a microbial culture without contamination.

Pure Culture

Holds only one isolated species of microorganism.

Contaminated Culture

Accidentally acquires unwanted microorganisms.

Growth on Agar Plate

Well-defined, isolated circular or irregular mounds (colonies).

Turbidity in Broth

Indicates cloudiness due to microbial growth.

Streak Plate Purpose

To isolate individual bacterial colonies.

Incubating Agar Plates Upside Down

Prevents condensation from dripping onto the agar surface.

T-Streak Procedure

Divides plate into sections to dilute bacteria and isolate colonies.

Colony Definition

A visible cluster of genetically identical cells originating from a single mother cell.

Oxidase Test Enzyme

Tests for Cytochrome c oxidase presence.

Aerobic Energy Test Result

Positive for oxidase due to oxygen as terminal electron acceptor.

Anaerobic Energy Test Result

Negative for oxidase as it does not use oxygen.

Positive Oxidase Test

Turns purple indicating presence of cytochrome c oxidase.

Triple Sugar Iron (TSI) Ingredients

Contains glucose, lactose, sucrose, and proteins like peptones.

Acid Production in TSI Test

Produced by fermentation, causing a color change in the medium.

TSI Black Coloring

Indicates hydrogen sulfide production in the media.

Mannitol Salt Agar Selectivity

High salt concentrations inhibit most except salt-tolerant bacteria.

Mannitol Salt Agar Differentiation

Fermentation leads to a color change indicating acid production.

Catalase Test Reagent

Hydrogen peroxide is used to identify catalase production.

Why Bubbles in Catalase Test

Catalase breaks down hydrogen peroxide into water and oxygen gas.

Catalase-Positive Test

Presence of bubbles indicates ability to detoxify hydrogen peroxide.

Catalase-Negative Test

No bubbles show inability to break down hydrogen peroxide.

Coliform Definition

Gram-negative, rod-shaped bacteria that ferment lactose with gas production.

MacConkey Agar Function

Selective for Gram-negative bacteria and differential for lactose fermentation.

EMB Agar Characteristic

E. Coli shows metallic green sheen due to vigorous lactose fermentation.

Zone of Inhibition

Clear area around antibiotic disk indicating susceptibility or resistance.

Broad-Spectrum Antibiotics

Effective against a wide variety of both Gram-positive and Gram-negative bacteria.

Narrow-Spectrum Antibiotics

Effective against a limited group of bacteria.