Bacteria Identification Under a Microscope
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Questions and Answers

What is the shape of the bacteria in the first row?

  • Irregular
  • Rod-shaped
  • Spherical (correct)
  • Squiggle-shaped

Why are the bacteria in the third row viewed using dark field microscopy?

  • Because they are Gram-positive
  • Because they are motile
  • Because they do not stain the same way as other bacteria (correct)
  • Because they are too small to be seen with a light microscope

What is the term for a single bacterium with a spherical shape?

  • Coccus (correct)
  • Cocci
  • Spirillum
  • Bacillus

What is the appearance of the bacteria in the second row?

<p>Rod-shaped (B)</p> Signup and view all the answers

Why are the bacteria in the first row purple in color?

<p>Because of the type of dye used (C)</p> Signup and view all the answers

What is the term for multiple bacteria with a spherical shape?

<p>Cocci (B)</p> Signup and view all the answers

Why is it necessary to view the bacteria in the third row using a different method?

<p>Because they do not stain the same way as other bacteria (A)</p> Signup and view all the answers

What is the shape of the bacteria in the third row?

<p>Squiggle-shaped (B)</p> Signup and view all the answers

What is the term used to describe a single rod-shaped bacterium?

<p>Bacillus (A)</p> Signup and view all the answers

What is the purpose of the Gram stain in studying bacteria?

<p>To differentiate between Gram positive and Gram negative bacteria (A)</p> Signup and view all the answers

What is the characteristic of the cell wall in Gram positive bacteria?

<p>Thick and composed of peptidoglycan (D)</p> Signup and view all the answers

What is the function of the lipopolysaccharide layer in Gram negative bacteria?

<p>To maintain the cell's outer membrane structure (A)</p> Signup and view all the answers

What is the term used to describe a single spiral-shaped bacterium?

<p>Spirochete (D)</p> Signup and view all the answers

What is the main difference between the cell walls of Gram positive and Gram negative bacteria?

<p>Peptidoglycan layer thickness (D)</p> Signup and view all the answers

What is the purpose of the capsule layer in bacterial cells?

<p>To protect the cell from environmental stress (B)</p> Signup and view all the answers

What is the term used to describe the combination of sugar chains and peptides in bacterial cell walls?

<p>Peptidoglycan (C)</p> Signup and view all the answers

What is the main component of the outer membrane in Gram negative bacteria?

<p>Lipopolysaccharide layer (B)</p> Signup and view all the answers

What is the term used to describe the staining result of Gram positive bacteria?

<p>Purple (A)</p> Signup and view all the answers

What is the layer above the plasma membrane in a bacterium?

<p>Capsule (D)</p> Signup and view all the answers

What is the name of the space between the plasma membrane and the peptidoglycan layer?

<p>Periplasmic space (A)</p> Signup and view all the answers

What is the reason why Gram negative bacteria stain pink?

<p>Because they have a thin peptidoglycan layer (D)</p> Signup and view all the answers

What is the purpose of the Gram stain?

<p>To determine the cell wall structure of bacteria (B)</p> Signup and view all the answers

What is the characteristic of the peptidoglycan layer in Gram positive bacteria?

<p>It is thick (C)</p> Signup and view all the answers

What is the name of the substance used to restain Gram negative bacteria?

<p>Safranin (C)</p> Signup and view all the answers

What is the location of the polysaccharides in a bacterium?

<p>At the top of the cell wall (C)</p> Signup and view all the answers

What is the term for the region next to the plasma membrane?

<p>Periplasmic (A)</p> Signup and view all the answers

Flashcards

Coccus

Single bacterium with a spherical shape.

Cocci

Multiple bacteria with a spherical shape.

Bacillus

Single rod-shaped bacterium.

Spirochete

Single spiral-shaped bacterium.

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Gram Positive Cell Wall

Thick and composed of peptidoglycan.

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Gram Negative Cell Wall

Thin layer of peptidoglycan, covered by an outer membrane.

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Gram Staining

To differentiate between Gram positive and Gram negative bacteria.

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Capsule

Layer above the plasma membrane in a bacterium.

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Capsule Function

To protect the cell from environmental stress.

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Peptidoglycan

The combination of sugar chains and peptides in bacterial cell walls.

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Lipopolysaccharide Layer

The main component of the outer membrane in Gram negative bacteria.

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Periplasmic Space

The space between the plasma membrane and the peptidoglycan layer.

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Gram Negative Staining Pink

Because they have a thin peptidoglycan layer.

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Purpose of Gram Stain

To determine the cell wall structure of bacteria.

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Peptidoglycan Layer in Gram Positive Bacteria

It is thick.

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Safranin

Used to restain Gram negative bacteria.

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Location of Polysaccharides

At the top of the cell wall.

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Periplasmic

Region next to the plasma membrane.

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Study Notes

Bacteria Shapes

  • Bacteria can have different shapes, including:
    • Coccus (singular) or Cocci (plural): spherical shape
    • Bacillus (singular) or Bacilli (plural): rod-shaped
    • Spirochete (singular) or Spirilla (plural): spiral-shaped

Gram Staining

  • The Gram stain is a special stain used to distinguish between bacteria
  • It stains the outside of the bacteria
  • If the stain is retained, the bacteria is Gram positive and appears purple
  • If the stain is washed off and restained with Safranin, the bacteria is Gram negative and appears pink

Gram Positive Bacteria

  • Have a thick peptidoglycan layer in their cell wall
  • The peptidoglycan layer is made up of long chains of sugars (glycan) connected by proteins (peptide)
  • This layer is responsible for retaining the Gram stain, making the bacteria appear purple
  • Gram positive bacteria also have a plasma membrane and a capsule or slime layer

Gram Negative Bacteria

  • Have a thin peptidoglycan layer in their cell wall
  • The thin peptidoglycan layer is washed off by the Gram stain, making the bacteria appear pink after restaining with Safranin
  • Gram negative bacteria have an outer membrane, a lipopolysaccharide (LPS) layer, and a capsule or slime layer
  • The LPS layer is composed of lipids and polysaccharides

Cell Wall Structure

  • Gram positive bacteria have a thick peptidoglycan layer, a plasma membrane, and a capsule or slime layer
  • Gram negative bacteria have a thin peptidoglycan layer, an outer membrane, an LPS layer, and a capsule or slime layer

Key Differences

  • Gram positive bacteria have a thick peptidoglycan layer, while Gram negative bacteria have a thin peptidoglycan layer
  • Gram positive bacteria retain the Gram stain, while Gram negative bacteria are washed off and restained with Safranin
  • The cell wall structure of Gram positive and Gram negative bacteria differs significantly

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Description

Examine bacteria samples under a microscope and identify their characteristics, including color and shape, to differentiate between them.

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