Lecture 5: Cell Structure

Question 1

What are the two storage structures in bacteria and what do they store? Give bacterial examples.

Answer 1

1. Poly-hydroxybutyrate, glycogen - carbon storage (Ralstonia eutropha)
2. Polyphosphate granules - phosphate storage

Question 2

What are gas vesicles, what do they do, and what are they made of?

Answer 2

Gas vesicles are a form of bouyancy regulator, allowing bacteria to alter how much they ‘float’. They are made of proteins and are GAS PERMEABLE but NOT WATER PERMEABLE.

Question 3

What do magnetosomes do? What are they composed of?

Answer 3

Function: orientation of the bacterium
Composition: magnetite particles

Question 4

What is meant by the term magneto-taxis?

What is the purpose of using northern and southern hemispheres to magneto-tax? What bacteria can this be seen in?

Answer 4

Magneto-taxis: orienting and coordinating movement in relation to earths magnetic field

This allows cells to efficiently find their optimum oxygen concentration at the microaerobic oxic-anoxic transition zone (OATZ) in water columns. Alters whether their flagella move clockwise or counter clockwise

Gram negative bacteria

Question 5

What are endospores? what bacteria can this be seen in?

Answer 5

A second form of life cycle phase in some gram-negative bacteria, occurs during SPORULATION.

Very hardy.

Question 6

What are external bacterial structures? what do they do?

Answer 6

1. Flagellum - movement: used in various ways to provide movement
2. Pili (fimbrae) - 10-250/cell; attachment, sex, and motility

Question 7

What are axial filaments? Where are they seen within the cell? How do they work?

Answer 7

Also termed “endoflagella”.
They are located between cell wall and outer sheath (periplasmic)
They are anchored at one cell wall and rotation causes cell to move like a cork screw

Question 8

What is the Glycocalyx coat? What is it composed of?

Answer 8

A slimey outer layer.

It is a glycoprotein coat (protein and carbohydrates)

Question 9

What are the two forms of glycocalyx coat?

Answer 9

1. Slime (loosely attached coat) - easily washed off - cause problems in industries with pipes where they leave and abundance of slime (plumbing)
2. Capsule (firmly attached coat) - can be seen with gram stains

Question 10

What are the functions of the glycocalyx?

Answer 10

1. Protection against: drying, phagocytosis, buffer between cell-environment
2. Adhesion
3. Cell-cell communication
4. Modulation of immune responses
5. Pathogenicity