Lecture 3

Question 1

What are the characteristics of eukaryotes

Answer 1

Eukaryotes have 80s (60s and 40s ) , it has a well defined nucleus , and membrane bound organelles as well as a linear genome

Question 2

What are the characteristic’s of prokaryotes

Answer 2

• 70s ribosomes (50s and 30s )
• circular genome
• no membrane bound organelles
• AMR genes

Question 3

What are plasmids

Answer 3

• Plasmids carry genes that are antimicrobial

- small , circular double stranded DNA

Question 4

What are the different bacterial shapes

Answer 4

Cocci- Circular

Basilar- Rod like

Question 5

What is the gram staining process

Answer 5

• Heat fix
• Stain(Crystal Violet)
• Iodine treatment
• Destain with alcohol
• Safranin(counter stain ) `

Question 6

Which gram stains purple

Answer 6

Gram positive

Question 7

Which gram stains pink

Answer 7

Gram negative

Question 8

How many layers does gram negative and gram positive have

Answer 8

Gram negative - 2 ( outer membrane and periplasmic layer)

Gram positive - 1

Question 9

Why is there a color difference between the gram positive and negative

Answer 9

The peptidoglycan layer retains the crystal violet of the gram stain and because the gram positive has a thicker layer of peptidoglycan it retains the stain

Question 10

Gram positive features

Answer 10

• Thick peptidoglycan layer
• Teichoic acid
• Lipoteichoic acid

Question 11

Gram negative features

Answer 11

• Thin Peptidoglycan
• outer membrane
• porins
• LPS

Question 12

Where can we find the LPS

Answer 12

outer membrane of the gram negative (cell wall)

Question 13

What are the components of the LPS

Answer 13

• O- antigen ( for identification of species)
• Core Polysaccharide
• Lipid A (toxic effect)

Question 14

What is the function of the LPS

Answer 14

Functions as an endotoxin which triggers inflammation and leads to sepsis

Question 15

What is the peptidoglycan layer composed of :

Answer 15

repeating subunits of NAM and NAG crosslinked by the sugars and trans-peptide bridges

Question 16

What is a major target for B lactam drugs , give an example of such drugs

Answer 16

• Penicillin Binding Proteins (Transpeptidases )

- e.g , penicillin (similar structure )

Question 17

What’s an example of a transpeptidase that is resistant to Penicillin

Answer 17

PBP2a = MRSA

Question 18

What are the three ways bacteria generates energy and what are the final electron accepters of them

Answer 18

Aerobic - O2(36-38ATP )
Anaerobic - Sulphur
Fermentation - using organic compounds as an e- acceptor (2ATP)

Question 19

I am gram positive , rod shaped , and aerobic who could I be ?

Answer 19

Listeria
Bacillus
Corynebacterium

Question 20

I am gram positive ,rod shaped and I am anaerobic , who am I ?

Answer 20

Clostridium

Question 21

I am gram positive ,circular and I am catalase negative who am I and , how can you treat me

Answer 21

• streptococcus

- penicillin

Question 22

I am gram positive, circular and I am catalase positive who am I and , how can you treat me

Answer 22

Staphylococcus , do a sensitivity test

Question 23

I am gram negative , diplococci and aerobic , what am I ?

Answer 23

Neisseria

Question 24

I am gram negative , bacilli , not lactose fermenting , I do not produce H2S

Answer 24

Shigella

Question 25

I am gram negative , bacilli , non lactose fermenting , I produce H2S

Answer 25

Salmonella

Question 26

I am comma shaped , oxidase positive and I produce urease , who am I ?

Answer 26

Helicobacter