L10: Genetics of Bacteria

Question 1

Bacteria is grown in…

Answer 1

Liquid medium
Agar plate

Question 2

2 types of media

Answer 2

1) Nutrient broth
2) Minimal media

Question 3

3 bacterial growth phases

Answer 3

1) Lag phase
2) Exponential (log) phase
3) Stationary phase

Question 4

Which phase of bacterial growth is characterised by rapid cell division?

Answer 4

Lag Phase

Question 5

What happens during the exponential/log phase?

Answer 5

Period of rapid growth where bacteria are dividing in a fixed time interval (doubling time)

Question 6

What happens during the stationary phase?

Answer 6

Cells stop dividing due to limited nutrients

Question 7

How does wild type E. coli grow on minimal media?

Answer 7

By synthesizing all necessary components from minimal media

Question 8

3 methods of genetic (DNA) exchange between bacteria

Answer 8

1) Transformation
2) Transduction
3) Conjugation

Question 9

Describe transformation in bacterial DNA exchange

Answer 9

uptake of DNA fragments by bacteria from the environment

Question 10

Describe transduction in bacterial DNA exchange

Answer 10

Gene transfer via bacteriophages

Question 11

Describe conjugation in bacterial DNA exchange

Answer 11

Direct transfer of DNA via cell-to-cell contact/conjugation pilus

Question 12

Define natural competency

Answer 12

Specific physiological state in which prokaryotes are able to take up genetic material

Question 13

2 features of natural competency in transformation in bacterial DNA

Answer 13

1) only a small fraction of bacterial cells naturally take up DNA

2) competency is only induced in a lab using CaCl2 treatment

Question 14

How does the environment influence the competency of bacteria for transformation?

Answer 14

The bacterial growth state

Question 15

Process of transforming plasmid into competent E.coli cells

Answer 15

• Incubate competent cell
• Heat shock at 47 degrees for 30s to encourage plasmid to enter cell
• Place back in ice
• Place on selective agar media plate
• Incubate for 24 hrs at 37 degrees

Question 16

Structure difference between T4 phage & lambda phage

Answer 16

T4 phage contains tail fibers, base plate
Lambda phage doesnt have tail fibers, base plate

Question 17

What is the significance of the lag phase in bacterial growth?

Answer 17

Bacteria are adapting to the new media

Question 18

What happenns when generalised transduction occur?

Answer 18

1) Host bacteria with 2 genes
2) Phage fuses with enzyme that chops genome into bits

3) A virus picks up a piece of host genomic DNA that is the same size as its own and transports it to another cell

4) virus infects cell injecting bacterial chromosme into the cell

5) digested by cellular digestases to become a transduced bacterium

Question 19

How does the presence of introns differ between bacterial and eukaryotic genomes?

Answer 19

Bacterial genomes typically lack introns

Question 20

What are the four phases of bacterial growth in culture?

Answer 20

Lag phase, exponential phase, stationary phase, death phase

Question 21

What is the significance of homologous recombination in bacterial genetics?

Answer 21

To integrate transferred DNA into the chromosome

Question 22

What is the significance of studying the complete DNA sequence of E. coli?

Answer 22

It provides insights into fundamental genetic principles

Question 23

What is the importance of operons in bacterial genomes?

Answer 23

Coordinating the expression of related genes

Question 24

What happens to arg- E. coli when grown on minimal media without added arginine?

Answer 24

will not grow

Question 25

What features characterize the F plasmid in E. coli?

Answer 25

Transfer genes, oriV, oriT, and IS

Question 26

What happens to the recipient cell during conjugation with an F+ cell?

Answer 26

Becomes an F+ cell

Question 27

Describe the discovery of conjugation using Y-24 & Y-10

Answer 27

Individual growth of Y-24 & Y-10 grown on complete medium showed no growth Mixed Y-24 & Y-10 showed colony growth

Question 28

What does conjugation require the physical contact between?

Answer 28

Donor (F+) & Recipient (F-) cells

Question 29

How is genetic information transferred through in conjugation?

Answer 29

hollow tube made of proteins (conjugation pilus/conjugation tube/sex pilus)

Question 30

What does F plasmid carry?

Answer 30

Genes which enable genetic exchange by conjugation

Question 31

Features of the F plasmid

Answer 31

1) Approx 30 transfer (tra) gene 2) An origin of replication (oriV) 3) An origin of transfer (oriT) 4) 3 insertion sequences (IS)

Question 32

Mechanism of the F plasmid by conjugation

Answer 32

1) F+ cell has a conjugation pilus that attaches to the F- cell 2) One strand of F plasmid (T strand) is transferred into the F- cell 3) Single strand nick produced at oriT 4) Both cells become F+

Question 33

When does the F plasmid integrate?

Answer 33

When a homologous recombination event occurs between 1 of its IS sequences & 1 of the several IS sequences

Question 34

What distinguishes Hfr strains from F+ strains in E. coli?

Answer 34

Hfr strains have the F plasmid integrated

Question 35

How does the lytic cycle of T4 phage affect bacterial cells?

Answer 35

It causes bacterial cell lysis