Module Four, Lecture Thirty Three

Question 1

What is a bacterial genome?

Answer 1

The complete set of DNA within a single bacterial cell ( including the main chromosome and plasmids )

Question 2

How big are bacterial genomes?

Answer 2

0.7 - 10 Mb ( megabase )

Question 3

Describe the structure of a bacterial genome ( 4 )

Answer 3

1. Single circular chromosome
2. No nuclear membrane, chromosome is located in the nucleoid
3. Plasmids ( self-replicating DNA molecules ) are found in the cytosol
4. The genetic material ( DNA ) is a double stranded helix, organised into compact superhelical structures ( rope )

Question 4

What is horizontal gene transfer?

Answer 4

Directly from one organism to another

Question 5

What is vertical gene transfer?

Answer 5

From ‘parent’ to ‘offspring’

Question 6

What are the two important attributes transferred horizontally by bacteria? ( 2 )

Answer 6

1. Virulence Factors
2. Antibiotic Resistance

Question 7

What are Virulence Factors?

Answer 7

A gene product that enables a microorganism to establish itself on or within a host of a particular species and enhance its potential to cause disease

Question 8

What is Antibiotic Resistance?

Answer 8

Bacteria evolve and change, developing the ability to survive exposure to antibiotics that were once effective

Question 9

What are the types of horizontal gene transfer in bacteria? ( 3 )

Answer 9

1. Transformation
2. Transduction
3. Conjugation

Question 10

What is Transformation?

Answer 10

Transformation involves uptake of short fragments of naked DNA by naturally transformable bacteria

Question 11

What is Transduction?

Answer 11

Transduction involves transfer of DNA from one bacterium into another via bacteriophages

Question 12

What is Conjugation?

Answer 12

Conjugation involves transfer of DNA material via sexually pilus and requires cell-to-cell contact

Question 13

What is Phage Therapy?

Answer 13

Phage therapy is the therapeutic use of bacteriophages ( viruses that specifically kill bacteria ) to treat pathogenic bacterial infections

Question 14

What are some advantages of Phage Therapy? ( 5 )

Answer 14

1. Only affects targeted bacterial species
2. Replicates at the site of infection
3. Occurs natural / easy to locate
4. Safe ( no serious adverse effects )
5. Active against antibiotic-resistant bacteria

Question 15

What are some disadvantages of Phage Therapy? ( 5 )

Answer 15

1. Lack of studies
2. Development of phage resistance and phage-neutralising antibodies
3. Not accessible to intracellular pathogens
4. Difficult to administer
5. Can transfer toxin genes between bacteria