First lab exam review

What is the HALO effect of the capsular stain?

The HALO effect refers to the appearance of a clear zone around a bacterial cell in 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 method is used to identify endospores, using malachite green as the primary stain.

Identify a negative stain.

Nigrosin is a common negative stain used to visualize cells against a clear background.

What are the different shapes of bacteria?

Bacteria can be classified into different shapes: cocci (spherical), bacilli (rod-shaped), spirilla (spiral), and vibrios (comma-shaped).

What are the different types of spores?

Types of spores include endospores, exospores, and arthrospores.

Example of enriched media.

Blood agar is an example of enriched media that supports the growth of a wide range of bacteria.

Definition of selective media.

Selective media are designed to allow the growth of certain types of bacteria while inhibiting others.

Why do we use immersion oil in microscopy?

Immersion oil is used to increase the resolution of the microscope by minimizing light refraction between the lens and the specimen.

What is a differential stain?

A differential stain is a technique that allows the differentiation of bacteria based on their staining properties.

What is the Gram stain?

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

Know the streak plate experiment.

The streak plate experiment is a technique used to isolate a pure culture from a mixed culture by spreading a diluted microbial sample over the surface of an agar plate.

What is calcium dipicolinic acid?

Calcium dipicolinic acid is a molecule found in bacterial endospores that stabilizes their structure and helps in dehydration.

Capsular composition.

Capsules are primarily composed of polysaccharides, though some may contain polypeptides.

Steps of endospore stain.

1. Prepare a heat-fixed smear. 2. Stain with malachite green and steam for 5 minutes. 3. Rinse with water. 4. Counterstain with safranin. 5. Rinse and observe.

Negative stain conditionalities.

Negative staining requires that the bacteria are live and unstained; it should not include heat-fixing to preserve cell morphology.

What is a simple stain?

A simple stain is a method that uses a single basic dye to color bacterial cells for microscopic observation.

What is a differential stain?

A differential stain is a staining process that distinguishes different types of bacteria based on their cellular structures.

Know the Ziehl Neelsen stain.

The Ziehl Neelsen stain is a differential stain primarily used to detect acid-fast bacteria, such as Mycobacterium species.

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 peptidoglycan layers and do not retain the stain, appearing pink.

What is differential media?

Differential media are formulated to demonstrate the differences between various organisms; they often include indicators that reveal biochemical properties.

Mannitol salt agar is selective for what?

Mannitol salt agar is selective for Staphylococcus species due to its high salt concentration.

What is a mixed culture?

A mixed culture contains two or more different types of microorganisms growing together.

What are the six I’s of culturing bacteria?

The six I's are Inoculation, Incubation, Isolation, Inspection, Information gathering, and Identification.

Definition of sterility.

Sterility is the absence of all living microorganisms, including bacterial spores.

What is a basic dye?

A basic dye is a type of dye that carries a positive charge and binds to negatively charged cells.

Examples of basic/acidic dyes.

Basic dyes include methylene blue and crystal violet, while acidic dyes include eosin and nigrosin.

Types of culture.

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

Know the flagella arrangement.

Flagella arrangements can be monotrichous (single flagellum), lophotrichous (cluster of flagella at one end), amphitrichous (flagella at both ends), or peritrichous (flagella distributed around the cell).

What is thioglycolate media?

Thioglycolate media is a type of medium that supports the growth of anaerobic and aerotolerant bacteria by creating a gradient of oxygen.

What is a structural stain?

Structural stains are used to highlight specific structures within a cell, such as capsules or endospores.

What is aseptic technique?

Aseptic technique refers to procedures implemented to prevent contamination of cultures and maintain sterility.