Microbiology Block A- Lecture 2

Front 1

How does HGT differ from VGT?

Back 1

Vertical gene transfer is the transfer of genetic material from parent to offspring

Hint 1

Horizontal gene transfer is the movement of genetic material between unicellular and/or multicellular organisms

Front 2

What is HGT?

Back 2

It is from one independent organism to another

Front 3

What is important in the evolutionary mechanism of many species?

Back 3

The ability to pass along genes using HGT

Front 4

What characteristics does stable recombinant have?

Back 4

Donor and recipient

Front 5

What are the three mechanisms that have evolved in bacteria to create recombinants?

Back 5

Transformation

Transduction

Conjugation

Front 6

Can bacteria that use HGT, transfer genes to the same or different species?

Back 6

Yes, they can transfer to the same or different species

Front 7

What are the fates of horizontally transferred genes?

Back 7

1. Population of stable recombinants

2. No stable recombinants

Front 8

What is transformation?

Back 8

It is the genetic transfer process by which DNA is incorporated into a recipient cell and brings about genetic change

Front 9

What is competent transformation?

Back 9

Competent cells are cells that are capable of taking up (naked/ foreign) DNA and being transformed.

Front 10

What are the (two) transformable bacteria?

Back 10

Bacillus and Neisseria

Front 11

What does strains of bacteria that are NOT naturally transformable do to make them competent?

Back 11

There are specific procedures that they can undergo to become transformable such as electroporation

Front 12

What is electroporation?

Back 12

It is when electricity is used to for cells to take up DNA for transformation

Front 13

What are the steps of natural transformation?

Back 13

1. Binding DNA

2. Uptake of single- stranded DNA

3. RecA-mediated homologous recombination

Front 14

During natural transformation what is highly regulated?

Back 14

Integration of transforming DNA is highly regulated

Front 15

What is transfection?

Back 15

Transformation of bacteria with DNA extracted from bacterial virus. Integration or replication of the bacteriophage

Hint 15

NOT to be confused with TRANSDUCTION

Front 16

What is transduction?

Back 16

The transfer of DNA from one cell to another by a bacteriophage due to mispackaging of the bacteriophage genome

Front 17

What are the two modes of transduction?

Back 17

1. Generalised transduction

2. Specialised transduction

Front 18

What is generalised transduction?

Back 18

DNA from any portion of the host genome is packed inside the virion

Front 19

What is specialised transduction?

Back 19

DNA from specific region of the host chromosome is integrated directly into the virus genome

Front 20

In generalised transduction what are the two characteristics of the virus?

Back 20

1. Virus can be temperate or virulent

2. Low efficacy

Front 21

In specialised transduction what are the two characteristics the DNA can show?

Back 21

1. DNA of temperate virus excises incorrectly and takes adjacent host genes along with it

2. Transducing efficiency can be high

Front 22

What is phage conversion in transduction?

Back 22

Alteration of the phenotype of a host cell by lysogenization

Front 23

What is non-defective temperate phage conversion?

Back 23

It is where a phage lysogenizes a cell and becomes a prophage

Front 24

Where are prophages apparent?

Back 24

They are apparent in bacterial genomes and are more comment than previously thought

Front 25

What happens to host cells after phage conversion?

Back 25

Host cells become immune to further infection by the same phage as they occupy the integration site this is called homoimmunity.

Other phenotypical changes can occur

Front 26

What is bacterial conjugation (mating)?

Back 26

It is a mechanism of verticle transfer that involves cell to cell contact

1. Plasma encoded mechanism

2. Donor cell

3. Recipient cell

Front 27

What is a donor cell in conjugation?

Back 27

A donor cell contains a conjugative plasmid

Front 28

What is a recipient cell in conjugation?

Back 28

A recipient cell does not contain a plasmid

Front 29

What are F (fertility) plasmids in conjugation?

Back 29

Circular DNA molecules that contain genes that regulate gene replication

Front 30

What are the three things that F plasmids contain?

Back 30

1. Genes that regulate DNA replication

2. Contain several transposable elements that allow host chromosome integration

3. Contains tra genes that encode transfer functions

Front 31

What are sex pilus’?

Back 31

They are essential for conjugation and are produced only by the donor cell

Front 32

In conjugation how does DNA synthesis occur?

Back 32

DNA is synthesised by rolling circle replication which is a mechanism also used by some viruses

Front 33

What type of plasmid is a episome?

Back 33

F (fertility) plasmid

Front 34

What is F plasmid able to do because it is an episome?

Back 34

It can integrate into the host chromosome

Front 35

What are cells that possess a Nonintegrated F plasmid called?

Back 35

F+

Front 36

What are cells that possess F plasmids called?

Back 36

Hfr

Front 37

What does Hfr stand for?

Back 37

High frequency of recombination

Front 38

What does Hfr mean?

Back 38

It means that it has high rates of genetic recombination between genes on the donor chromosome and those of the recipient

Hint 38

What does it do?

Front 39

What does the presence of the F plasmid result in?

Back 39

It results in alterations in cell properties

Front 40

What are the alteration in the cell properties that are a direct result of F plasmids?

Back 40

Ability to synthesise F pilus

Mobilisation of DNA for transfer to another cell

Alteration of surface receptors so that the cell can no longer act as a recipient in conjugation

Front 41

What do insertion sequences do?

Back 41

Facilitate homologous recombination

Plasmid is now part of chromosome

Front 42

Where are insertion sequences present?

Back 42

F plasmid and E. Coli chromosome

Front 43

Why does the recipient cell not become a Hfr cell?

Back 43

Because only a portion if the integrated F plasmid is transferred by the donor

Front 44

What causes genes to transfer in a different order?

Back 44

Hfr strains that differ in the integration position of the F plasmid in the chromosome transfer genes in different orders

Front 45

What can genetic crosses with Hfr strains be used for?

Back 45

They can be used to map the order of genes on the chromosome

Front 46

What are F’ plasmids?

Back 46

Previously integrated F plasmids that have excised and captured some chromosomal genes