microbiology lab exam reviw

What is the HALO effect of the capsular stain?

The HALO effect refers to the clear zone around a bacterial cell when viewed under a microscope after performing a capsular stain, indicating the presence of a capsule.

Identify a capsular stain.

An example of a capsular stain is the India ink stain.

Identify an endospore stain (Schaeffer Fulton).

The Schaeffer-Fulton stain is a method used to visualize endospores in bacterial cells, typically using malachite green and safranin.

Identify negative stain.

A negative stain is a staining technique that colors the background but leaves the bacterial cells uncolored, such as the India ink or nigrosin stain.

Different shapes of bacteria.

Bacteria can have various shapes including cocci (spherical), bacilli (rod-shaped), and spirilla (spiral-shaped).

What are the different types of spores?

Types of spores include endospores, exospores, and reproductive spores.

Example of enriched media.

An example of enriched media is blood agar, which contains nutrients and growth factors for fastidious organisms.

Definition of selective media.

Selective media is a type of growth medium that supports the growth of specific microorganisms while inhibiting others.

Why do we use immersion oil in microscopy?

Immersion oil is used to enhance the resolution of the microscope, as it reduces light refraction and improves clarity.

What is a differential stain?

A differential stain is a staining technique that differentiates between types of cells or structures, such as the Gram stain.

Know the Gram stain.

The Gram stain is a differential staining method that classifies bacteria into Gram-positive or Gram-negative based on their cell wall composition.

Know the streak plate experiment.

The streak plate experiment is a technique used to isolate a pure culture from a mixed sample by streaking it across an agar plate.

What is calcium dipicolinic acid?

Calcium dipicolinic acid is a component found in bacterial endospores that helps stabilize and protect the spore's structure.

Capsular composition.

Capsules are composed primarily of polysaccharides or polypeptides that protect bacteria from phagocytosis.

Steps of endospore stain.

The steps of the endospore stain include: 1) Heat fix, 2) Stain with malachite green, 3) Steam for 5 minutes, 4) Rinse with water, 5) Counterstain with safranin.

Negative stain conditionalities.

Negative staining conditions include using a dye that does not penetrate the cell, such as India ink, and requires a clean, dry slide.

What is a simple stain?

A simple stain is a basic staining method that imparts color to the cells to allow visualization without distinguishing between different types.

What is a differential stain?

A differential stain is used to distinguish between different types of bacteria or cellular structures based on their staining properties.

Know the Ziehl-Neelsen stain.

The Ziehl-Neelsen stain, also known as acid-fast stain, is used to identify Mycobacterium species and differentiates them from other bacteria.

Differences between Gram positive and Gram-negative bacteria.

Gram-positive bacteria have thick peptidoglycan layers and retain the crystal violet stain, while Gram-negative bacteria have thin layers and do not retain the stain.

What is differential media?

Differential media is a type of culture medium that allows differentiation of microorganisms based on observable changes, such as color changes.

Mannitol salt agar is selective for what?

Mannitol salt agar is selective for Staphylococcus species, particularly Staphylococcus aureus.

What is a mixed culture?

A mixed culture is a culture containing two or more different species of microorganisms.

The six I’s of culturing bacteria.

The six I’s of culturing bacteria are Isolation, Incubation, Inspection, Identification, Information gathering, and Inoculation.

Sterility.

Sterility is the absence of all living microorganisms, achieved through methods such as autoclaving.

What is a basic dye?

A basic dye is a positively charged dye that binds to negatively charged cellular components, commonly used in staining techniques.

Examples of basic/acidic dye.

Examples of basic dyes include crystal violet and methylene blue; examples of acidic dyes include eosin and nigrosin.

Types of culture.

Types of culture include pure culture, mixed culture, and enriched culture.

Know the flagella arrangement.

Bacterial flagella can be arranged in various ways, including monotrichous (single), lophotrichous (tufts), amphitrichous (at both ends), and peritrichous (all over).

Thioglycolate media.

Thioglycolate media is a reducing medium used to grow anaerobic and microaerophilic bacteria by maintaining a reduced environment.

Structural stain.

A structural stain is a staining technique used to visualize the structures within a cell, such as flagella or endospores.

Aseptic technique.

Aseptic technique refers to practices used to prevent contamination by pathogens during laboratory procedures.