Microbiology Lecture 3

Question 1

Do all bacteria have cell walls?

Answer 1

Most do, some like mycoplasma do not.

Question 2

True or false

Fimbriae are used in locomotion.

Answer 2

False, main use is in attachment/adhering.

Question 3

True or false

Flagella are used in locomotion,

Answer 3

True.

Question 4

Define glycocalyx.

Answer 4

A capsule or slime layer external to the cell wall.

Question 5

What is a glycocalyx made from?

Answer 5

Polysaccharides, sometimes polypeptides or both.

Question 6

What allows the difference in glycocalyx structure?

Answer 6

If arranged tightly, it is a capsule, if loose, it is a slime layer.

Question 7

What is the purpose of the glycocalyx?

Answer 7

Allows attachment to surfaces forming a biofilm.

Encapsulated bacteria are also more difficult to kill.

Question 8

How can encapsulated bacteria be stained?

Answer 8

Negative staining on the bacteria, and then a background stain to reveal the capsule.

Question 9

What does attachment of bacteria to surfaces activate?

Answer 9

Biofilm-specific genes, including cell-cell signalling molecules.

Question 10

What is the function of pili?

Answer 10

Involved in genetic transfer between bacteria via conjugation.

Question 11

What is the function of fimbriae?

Answer 11

Enables bacteria to attach to surfaces and form biofilms.

Question 12

What are fimbriae like compared to flagella?

Answer 12

Fimbriae are shorter, straighter, and thinner than flagella.

Question 13

What are pili like compared to fimbriae?

Answer 13

Longer than fimbriae, only a few present on the surface.

Question 14

How do flagella induce motion?

Answer 14

By rotating.

Question 15

What are flagella powered by?

Answer 15

A motor - a rod surrounded by a series of rings.

Question 16

Do flagella induce an immune reaction?

Answer 16

Yes.

Question 17

What are the subunits and structure of flagella?

Answer 17

Are helices, made of flagellin subunits.

Question 18

From where does the flagella extend?

Answer 18

Extends from the cytoplasmic membrane, through the cell wall.

Question 19

How do bacteria know where to move?

Answer 19

Chemotaxis using chemoattractants/repellents.

Question 20

Name and define the 4 types of flagella.

Answer 20

Monotrichous - single
Lophotrichous - tuft at one end
Polar - one at each end
Peritrichous - many located around the cell

Question 21

Define the three types of motion seen in a hanging drop test.

Answer 21

Brownian motion - not true motility, caused by bacteria colliding with water.
Streaming motility - not true motility, caused by currents in the water.
True motility - bacteria will move in different directions, not all in the same direction.

Question 22

Aside from a hanging drop test, how else can bacteria be tested for motility?

Answer 22

Use semisolid media.
Motile bacteria will show diffuse growth through the tube.
Non-motile bacteria will only grow at the inoculation point.

Question 23

Define sporulation.

Answer 23

Endospore production.

Question 24

What prompts sporulation?

Answer 24

Desiccation.

Question 25

Where are endospores mostly found?

Answer 25

In soil bacteria.

Question 26

Do endospores stain?

Answer 26

Not with the typical ones.

Question 27

Are endospores toxic?

Answer 27

They can be during sporulation or germination. Proteins required for these processes may be toxic - indirect.

Question 28

How are endospores dehydrated?

Answer 28

Contain dipicolinic acid, which complexes with calcium ions to dehydrate it.

Question 29

What do cyanobacteria have to help them float and why?

Answer 29

Gas vacuoles for light exposure - photosynthesis.

Question 30

What are the surface lipids of mycobacteria made of, and why dont gram stains work on them? What is a way of staining them?

Answer 30

Mycolic acid, cant be gram stained as it is water-based. Need a lipid-based stain like acid-fast stain.