Lecture 1&2 The Bacterial Cell

Question 1

Describe the shape of a Cocci Bacteria

Answer 1

Grape-like
Spherical
E.g Streptococci

Question 2

Define Opsonisation

Answer 2

The process in which the immune system tags pathogens with opsonins for elimination by phagocytes

Question 3

What is the sugar coated capsule’s role around a bacterium?

Answer 3

The capsule protects the cell wall of the bacterium. The immune system no longer recognises the bacterium which helps them proliferate more

Question 4

What is the role of fimbriae/pili?

Answer 4

Helps attach to surfaces. I.e sex pili bring cells into close contact in order for genetic exchange of plasmids (exchanging RNA)

Question 5

What is the role of the bacterial flagella?

Answer 5

Helps move towards the nutrients and away from danger

Question 6

What is chemotaxis?

Answer 6

The motion of cells towards nutrients and away from toxic conditions. The flagella helps propel the movement.

Question 7

What is the name of the bond between the two hydrophilic heads?

Answer 7

Ester bond

Question 8

What’s the difference between gram-positive and gram-negative bacteria?

Answer 8

Gram-positive bacteria only have peptidoglycan cell walls and are more susceptible to antibiotics than gram-negative. Gram-negative have thinner peptidoglycan (glyco-protein) surrounded by an outer layer of lipoprotein and lipopolysaccharide.

Question 9

What colour does gram-positive bacteria stain and why?

Answer 9

The cell walls stain purple as the peptidoglycan retains the crystal violet dye.

Question 10

What colour does gram-negative bacteria stain and why?

Answer 10

They have less peptidoglycan, the cell wall doesn’t retain the crystal violet dye and stains red due to the background stain.

Question 11

Where do you find Lipid A?

Answer 11

Lipid A is the monomer head of the lipopolysaccharide

Question 12

What symptoms is Lipid A responsible for?

Answer 12

1) Black spots on the skin
2) Can cause a cytokine storm
3) Causes blood to clot
4) Can cause amputations due to the surrounding cells dying from a lack of oxygen

Question 13

What is the difference between gram-positive and gram-negative peptidoglycan?

Answer 13

Gram-positive peptidoglycan contains pentaglycine cross-links
Gram-negative peptidoglycan contains direct cross-links

Question 14

Define Virulent

Answer 14

The ability for a pathogen to cause damage to a host

Question 15

How many base pairs do viruses have?

Answer 15

200 bp

Question 16

What is the cytoplasmic bridge used for?

Answer 16

The transfer of a single-stranded copy of the plasmid from one cell to another. Pilli are used to help the transfer.

Question 17

Describe the lysogenic cycle

Answer 17

1) Phage DNA enters cell
2) Phage DNA integrates and becomes prophage
3) Integrated prophage replicates within the cell
4) Prophage may separate and cell enters lytic cycle

Question 18

Describe the lytic cycle

Answer 18

1) Phage binds to the cell
2) Phage DNA enters host cell
3) Host DNA is digested
4) New phage DNA forms
5) Host transcribes and translates phage DNA, when the assembly is complete the encoded enzyme causes lysis.
6) New phages are released

Question 19

Name the toxin produced by Corynebacterium diphtheria

Answer 19

Diphtheria toxin

Question 20

Name the toxin produced by Clostridium boltulinum

Answer 20

Botulin

Question 21

Name the toxin produced by Vibrio cholerae

Answer 21

Choleratoxin

Question 22

Name the toxin produced by Clostridium tetani

Answer 22

Neurotoxin

Question 23

Name the toxin produced by E.coli

Answer 23

Enterotoxin

Question 24

Name the toxin produced by Staphylococcus aureus

Answer 24

Coagulase enterotoxin

Question 25

Name the toxin produced by Streptococcus mutans

Answer 25

Dextransucrase (tooth decay)

Question 26

The phenotypes for antibiotic resistance and toxin production are encoded where in pathogenic bacteria?

Answer 26

Plasmids

Question 27

Streptococcus pyogenes needs what to be able to produce the toxin causing scarlet fever?

Answer 27

Only Streptococcus pyogenes carrying a prophage are able to produce the toxin that causes scarlet fever

Question 28

Define transposon

Answer 28

Transposons are mobile DNA segments that can replicate and insert copies at sites within the same or different chromosome. They can cause the transmission of antibiotic resistant genes in bacteria

Question 29

Describe the cycle that occurs with endospore-forming bacteria

Answer 29

1) The endospore germinates, forming a vegetative cell
2) The vegetative cell forms an endospore (sporulation)
3) The forespore then turns into a mature endospore.
4) During germination the mature endospore can form a vegetative cell