Microscope, Colony Morphology, and Staining Techniques

Flashcards covering microscope usage, colony morphology, broth terminology, streak plate technique, bacterial morphology, and various staining techniques including Gram staining process and common issues.

Always with two hands: one on the arm and one supporting the base to prevent damage.

Carrying the microscope

On a flat, stable surface to ensure accurate viewing.

Placing the microscope

Must be lowered before placing the slide to avoid damage to the slide or lens.

Stage (Microscope use)

Starting objective power

The lowest-power objective (usually 4×) to locate the specimen easily.

Securing the prepared slide

On the stage using stage clips to prevent movement during observation.

Specimen position (Microscope use)

Over the light opening to ensure proper illumination.

Bringing objective lens to slide

While looking from the side to avoid contact.

Coarse adjustment knob

Used to bring the image into focus.

Fine adjustment knob

Used for clarity after using the coarse adjustment knob.

Oil immersion

Typically used with the 100× objective to enhance resolution.

Focusing before 100× objective

Focus the specimen using the 40× objective.

Application of immersion oil

Apply a small drop of immersion oil on the coverslip where the 100× lens will contact it.

Purpose of immersion oil

To reduce light refraction.

Focusing with 100× objective

Rotate the 100× objective into the oil and use fine adjustment to achieve focus.

Effect of oil on light refraction

Reduces light refraction, allowing more light to enter the objective lens, thus improving resolution.

Coarse adjustment with 100× oil-immersion objective

Never use it to prevent damage to the slide and lens.

Cleaning oil from objective and slide

Using appropriate lens paper after use.

Colony morphology

The characteristics of bacterial colonies on solid media, which can provide insights into the type of bacteria present.

Size (Colony morphology)

Key terms include small, medium, large.

Shape (Colony morphology)

Key terms include circular, irregular, filamentous.

Margin (Colony morphology)

Key terms include entire, wavy, lobate.

Elevation (Colony morphology)

Key terms include flat, raised, convex.

Color (Colony morphology)

Key terms include white, cream, yellow.

Plates (Culture)

Allow bacteria to grow as individual colonies on the surface, facilitating isolation and identification.

Slants (Culture)

Provide a larger surface area for growth by solidifying agar at an angle, with growth described along the slant/streak line.

Turbidity

Indicates a cloudy appearance due to bacterial growth throughout the broth.

Pellicle

Refers to growth at the surface of the broth.

Sediment

Describes growth that settles at the bottom of the broth.

Flocculent growth

Indicates clumps suspended throughout the broth.

Ring (Broth culture)

Indicates growth concentrated around the surface or rim of the broth.

Streak plate technique

Used to dilute bacteria across the surface of an agar plate to isolate individual colonies.

Proper streak plate technique

Ensures that fewer cells are transferred to each section, increasing the likelihood of isolated colonies.

Labeling a plate (Streak plate)

Label the bottom of the plate with necessary information to track samples.

Sterilizing the inoculating loop (Streak plate)

Before obtaining a small amount of bacterial culture using aseptic technique.

Streaking sections (Streak plate)

Streak the first section, sterilize the loop again, and rotate the plate to streak into a new section, repeating as necessary.

Purpose of sterilizing the loop (Streak plate)

Prevents contamination and ensures progressive dilution of bacteria.

Not gouging the agar (Streak plate)

Crucial as it can interfere with normal colony development.

Keeping the plate mostly closed (Streak plate)

Minimizes contamination from the environment.

Coccus

Spherical bacterial shape.

Bacillus

Rod-shaped bacterial shape.

Vibrio

Curved bacterial shape.

Spirillum

Spiral bacterial shape.

Spirochete

Flexible spiral bacterial shape.

Diplo- (Cocci arrangement)

Cocci arranged in pairs.

Strepto- (Cocci arrangement)

Cocci arranged in chains.

Staphylo- (Cocci arrangement)

Cocci arranged in clusters.

Tetrads (Cocci arrangement)

Cocci arranged in groups of four.

Sarcinae

Cocci arranged in cube-like packets.

Diplobacilli

Bacilli found in pairs.

Streptobacilli

Bacilli found in chains.

Morphology (Bacteria)

The combination of shape and arrangement, which is crucial for bacterial identification and classification.

Negative stain

Shows bacterial cells against a dark background, allowing for observation of size, shape, and arrangement without heat-fixing.

Negative stain usefulness

Useful for delicate structures that may be destroyed by heat.

Gram stain

Differentiates bacteria into Gram-positive (purple) and Gram-negative (pink/red) based on cell envelope structure.

Gram-positive bacteria (Gram stain)

Appear purple after Gram staining.

Gram-negative bacteria (Gram stain)

Appear pink/red after Gram staining.

Gram stain importance

A critical differential stain in microbiology, providing insights into bacterial classification and treatment options.

Capsule stain

Demonstrates the presence of a capsule surrounding certain bacterial cells, appearing as a clear halo against a stained background.

Capsule stain importance

Important for identifying pathogenic bacteria that possess capsules, which can enhance virulence.

Crystal Violet (Gram stain)

The primary stain that stains all cells purple initially.

Iodine (Gram stain)

A mordant that forms a complex with crystal violet, helping to trap the stain within the cells.

Alcohol/Acetone (Gram stain)

A decolorizer that differentiates cells; Gram-positive retain the stain, while Gram-negative become colorless.

Safranin (Gram stain)

A counterstain that stains the now-colorless Gram-negative cells pink/red, while Gram-positive cells remain purple.

Over-decolorization (Gram stain)

Can lead to false Gram-negative results.

Under-decolorization (Gram stain)

Can result in false Gram-positive results.