Micro Practical 1

Aseptic technique

Procedures used to prevent contamination.

Biohazard

Material that poses a biological risk.

Bunsen burner

Gas burner used for sterilization and heating.

Transfer

Moving microorganisms from one location to another.

Replicate

Repeated trial of an experiment.

Controls

Standard used for comparison.

Independent variable

Variable changed by the experimenter.

Dependent variable

Variable measured during an experiment.

Scientific method

Observation → Question → Hypothesis → Experiment → Analyze → Conclusion.

Ubiquity

Microorganisms are found almost everywhere.

Agar

Solid growth medium made from seaweed polysaccharides.

Nutrient agar

General-purpose agar for bacterial growth.

Broth

Liquid growth medium.

Petri dish

Shallow dish used to culture microorganisms.

Inoculating loop

Sterile wire loop used to transfer bacteria.

Micropipette

Instrument for measuring very small liquid volumes.

Micropipette tips

Disposable tips used with micropipettes.

Serological pipette

Pipette used to transfer milliliter volumes.

Weigh boat

Container used to hold materials for weighing.

Weigh balance

Instrument used to measure mass.

Vortex

Device used to mix liquid samples.

Test tube

Glass tube used to hold cultures or solutions.

Test tube rack

Holds test tubes upright.

Staining rack

Holds slides during staining.

Slide

Glass surface used to mount specimens.

Bibulous paper

Absorbent paper used to blot slides.

Immersion oil

Oil used with the 100× objective to improve image quality.

Lens paper

Special paper for cleaning microscope lenses.

Light microscope

Microscope that uses visible light.

Ocular lens

Eyepiece (usually 10×).

Objective lenses

Lenses that provide different magnifications

4x, 10x, 40x, 100x

Scanning objective

4× objective.

Low-power objective

10× objective.

High-power objective

40× objective.

Oil immersion objective

100× objective.

Total magnification

Ocular magnification × objective magnification.

Revolving nosepiece

Holds and rotates objective lenses.

Arm of microscope

Supports the microscope and is used for carrying.

Base

Bottom support of microscope.

Stage

Platform that holds the slide.

Condenser

Focuses light on the specimen.

Iris diaphragm

Controls light intensity.

Light source

Provides illumination.

Coarse adjustment knob

Brings specimen into rough focus.

Fine adjustment knob

Sharpens focus.

Parfocal

Image stays nearly focused when changing objectives.

Magnification

Enlargement of an object.

Resolution

Ability to distinguish two close objects.

Refraction

Bending of light.

Domain

Highest taxonomic level.

Kingdom

Classification below domain.

Bacteria

Prokaryotic domain.

Eukarya

Domain containing organisms with nuclei.

Protista

Kingdom of mostly unicellular eukaryotes.

Fungi

Kingdom of absorptive heterotrophs.

Animalia

Kingdom of multicellular animals.

Species

Most specific taxonomic classification.

Genus

Classification above species.

Prokaryote

Cell without a nucleus.

Eukaryote

Cell with a nucleus.

Nucleus

Membrane-bound organelle containing DNA.

Coccus

Spherical bacterium.

Bacillus

Rod-shaped bacterium.

Spirillum

Rigid spiral-shaped bacterium.

Spirochete

Flexible spiral bacterium.

Vibrio

Comma-shaped bacterium.

Cell morphology

Shape of bacterial cells.

Colony morphology

Overall appearance of colonies.

Colony forming unit (CFU)

One viable cell capable of forming a colony.

Margin

Edge of a colony.

Elevation

Side-view shape of a colony.

Umbonate

Raised center.

Lobate

Lobed edge.

Irregular

Uneven colony shape.

Punctiform

Very tiny colony.

Staphylo-

Grape-like clusters.

Strepto-

Chains.

Flagella

Structures used for bacterial movement.

Monotrichous

One flagellum.

Amphitrichous

One flagellum at each end.

Lophotrichous

Tuft of flagella at one end.

Peritrichous

Flagella surrounding the cell.

Simple stain

Colors all bacteria the same.

Differential stain

Distinguishes different bacteria.

Special stain

Highlights specific structures.

Gram stain

Differentiates bacteria by cell wall composition.

Primary stain

Crystal violet.

Crystal violet

First dye in Gram stain.

Mordant

Substance that fixes the stain.

Iodine

Mordant used in Gram staining.

Decolorizer

Alcohol/acetone removes stain from Gram-negative cells.

Alcohol/acetone

Gram stain decolorizer.

Counterstain

Second stain used for contrast.

Safranin

Counterstain in Gram staining.

Gram-positive bacteria

Purple after Gram stain.

Gram-negative bacteria

Pink after Gram stain.

Peptidoglycan

Thick cell wall layer in Gram-positive bacteria.

Heat fix

Attaches bacteria to slide before staining.

Bacterial smear

Thin bacterial sample spread on a slide.

Capsule stain

Detects bacterial capsules.