Introduction to Bacteria

Question 1

What do you need to use to see the entire structure of a bacteria cell?

Answer 1

Electron microscope.

Question 2

Discuss the structure of a bacteria cell.

Answer 2

Single cell, no nucleus.
Contains a cell wall, capsule and flagellum.
Cytoplasmic/inner/plasma membrane,.
Fimbriae

Question 3

What are fimbriae?

Answer 3

Long filamentous polymeric protein structures located at the surface of bacterial cells

Question 4

What is a flagellum?

Answer 4

Flagellum is primarily a motility organelle that enables movement and chemotaxis.
Bacteria can have one or several.

Question 5

Describe the cell membrane of a bacteria cell.

Answer 5

very thin, elastic and semi-permeable membrane

Question 6

Describe the structure of the cell wall of a bacteria cell.

Answer 6

Cell wall is rigid, giving the cell strength and shape but it is permeable.

Question 7

How can we differentiate between gram positive/negative cell walls?

Answer 7

Thicker layers of peptidoglycan indicates it is a gram positive cell wall.
Thinner layers of peptidoglycan indicates it is a gram negative cell wall.

Question 8

Some bacteria, like mycobacterium, cannot be reliably stained. Why?

Answer 8

They have a high lipid content.

Question 9

In light microscopy. when staining cells, what colour does-
1. Gram positive become
2. Gram negative become

Answer 9

1. Purple (think P=P)
2. Red

Question 10

What shape are cocci bacterium?

Answer 10

Small and round

Question 11

What shape are bacilli bacterium?

Answer 11

Rod shaped.

Question 12

What shape are spiral/corkscrew bacterium?

Answer 12

Haha lol spinal or corkscrew imagine that

Question 13

Describe the cytoplasmic membrane.

Answer 13

Made up of phospholipids (40%) and proteins (60%)
Forms a barrier but allows uncharged molecules and water to pass.
5-10nm thick

Question 14

Name the functions of the proteins in the cytoplasmic membrane.

Answer 14

-Transport systems for specific nutrients and ions.
-Enzymes to be involved in DNA replication, energy generation and cell wall synthesis.
-Sensing proteins which monitor conc. of molecules in the environment.

Question 15

Describe the cell wall of bacteria cells.

Answer 15

-10-25 nm thick
-Made of peptidoglycan
-Thick, strong and relatively rigid so maintains shape

Question 16

Which antibiotics can interfere w the construction of cell wall peptidoglycan?

Answer 16

Penicillin

Question 17

Where are penicillin binding proteins located?

Answer 17

Cell wall cytoplasmic membrane

Question 18

What is the action of penicillin?

Answer 18

Bind to the penicillin proteins and inhibit the bacterial cell wall synthesis.

Question 19

What happens if the bacterial cell wall is weakened?

Answer 19

Lysis- cell will swell and burst due to osmosis.

Question 20

How does the cell wall play a role in cell division?

Answer 20

Cross-walls form prior to separating into 2 daughter cells.

Question 21

Describe the LPS outer membrane.

Answer 21

-Only present in Gram negative bacteria
-Made up of LPS (lipopolysaccarides)
-Protects peptidoglycan from bile salts (in the gut), also from lysozyme
-Blocks many antibiotics getting into the cell
-Lipid A (within LPS) forms endotoxin, which, when released into the bloodstream (when multiplying or when lysed), may give rise to endotoxic shock.

Question 22

List to clinical symptoms categorised from endotoxic shock.

Answer 22

Fever and low blood pressure.

Question 23

Describe the capsule of bacteria cells.

Answer 23

-Polysaccharide layer outside the cell wall.
-Can be rigid or slimy(due to biofilm forming).

Question 24

What do rigid capsules do?

Answer 24

Prevent phagocytosis.

Question 25

What do slimy capsules do?

Answer 25

Produce a biofilm and adheres to cells.
Produces microcolonies which protect the cell.

Question 26

Describe the structure of flagella.

Answer 26

Long thin filament twisted into a spiral.
Often several times the length of the bacteria cells.
Cam be between 1-20.

Question 27

What do flagella do?

Answer 27

Provide the bacteria cell motility (regarding muscle contraction).

Question 28

Define Monotrichous in regards to number of flagella.

Answer 28

1 flagella.

Question 29

Define Lophotrichous in regards to flagella.

Answer 29

More than one flagella comes from one point.

Question 30

Define Amphitrichous in regards to flagella.

Answer 30

Multiple flagella from multiple points.

Question 31

Define -Peritrichous in regards to flagella.

Answer 31

All over.

Question 32

What are fimbriae?

Answer 32

Filaments.
Numerous compared to flagella.
Shorter and thinner than flagella.
Important role in adhesion between bacteria and host cells.

Question 33

How do bacteria cells replicate?

Answer 33

Using binary fission to produce two identical daughter cells.

Question 34

How can there be variation in bacterial cell replication?

Answer 34

-Spontaneous mutation.
-Transfer of DNA.

Question 35

Which enxymes cuts a section of the plasmid and where?

Answer 35

-Endonuclease at the origin of transfer.

Question 36

What is a bacteriophage?

Answer 36

A type of virus that infects bacteria.

Question 37

Describe ribosomes found in bacteria cells.

Answer 37

-Consist of RNA and associated proteins
-Function is to synthesise proteins

Question 38

Describe the number of ribosomes and related subunits.

Answer 38

Bacteria have a 70S ribosomes, with large (50S) and small (30S) subunits
The small 30S subunit has itself a subunit, called 16S.

Question 39

What happens in the highly resistant resting phase?

Answer 39

Occurs as a endospore
Organism can survive in a dormant state during a period of starvation..

Question 40

Describe the process of sporification.

Answer 40

1. Bacteria cells divides by binary fission.
2. DNA lines up along middle of the cell.
3. DNA of mother cell divides into two complete copies.
   4.Mother cell membrane engulfs developing spore.
   5.Developing pore is now surrounded by two membrane layers.
4. Calcium enters the cortex from the outside of the cell.
5. As calcium enters, water is removed from the spore.
6. Protein coat forms exterior to the cortex.
7. Spore becomes mature.
8. Some spores form an additional layer known as the exosporium.
9. Lytic enzymes destroy the mother cell and the mature spore is released.

Question 41

How are individual bacteria’s detected?

Answer 41

Sample is taken from patient and looked at under a microscope.
Stains are often used.