Bacterial genetics

Question 1

Bacterial genetics - transformation / aka

Answer 1

Ability to take up naked DNA (from cell lysis) from environment / AKA competence

Question 2

transformation (competence) - which bacteria?

Answer 2

many bacteria –> especially S. pneumoniae, H. influenzae type B, Neisseria

Question 3

transformation (competence) - which DNA is used

Answer 3

any DNA can be used

Question 4

how to avoid transformation in medium

Answer 4

add deoxyribonuclease to environment –> to degrade naked DNA

Question 5

bacterial Conjunction - types

Answer 5

1. F+ x F-

2. Hfr x F-

Question 6

F+ bacteria vs F- bacteria?

Answer 6

F+: bacterial with plasmid contains genes required for sex pilus and conjugation
F-: bacterial without plasmid contains genes required for sex pilus and conjugation

Question 7

F+ x F- conjunction?

Answer 7

sex pilus on F+ bacterium contacts F- bacterium. A SINGLE strand of plasmid DNA is transferred across the conjugal bridge (aka the mating bridge)

Question 8

F+ x F- conjunction - what is transferred and what is not transferred

Answer 8

A SINGLE strand of plasmid DNA is transferred

NO TRANFER OF CHROMOSOMAL DNA

Question 9

F+ x F- conjunction - transfer across

Answer 9

the conjugal bridge (aka the mating bridge)

Question 10

Hfr bacteria?

Answer 10

F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell

Question 11

Hfr x F- conjugation?

Answer 11

replication of incorporated DNA may include some flaking chromosomal DNA –> transfer of plasmid and chromosomal

Question 12

bacterial transposition?

Answer 12

segment of DNA (transposon) that can jump (excision and reintergation), can trafer genes from plasmid to chromosome and vise versra. When excision occurs, may include some flanking chromosomal DNA, which can incorporated into a plasmid transferred to another bacterium

Question 13

tranfer of a gene from a bacterium to another bacterium through transposition (examples)

Answer 13

vanA gene from vancomycin-resistant Enterococcus to S. aureus

Question 14

bacterial transduction - types

Answer 14

1. Generalized

2. Specialized

Question 15

bacterial generelized transduction?

Answer 15

a packaging event. Lytic phage infects bacterium, leading to cleavage of bacterial DNA. Parts of bacterial dna may become packaged in viral capsid. Phage infects another bacterium, transferring these genes

Question 16

bacterial specialized transduction?

Answer 16

an excision event. Lysogenic phage infects bacterium. viral DNA incorporates into bacterial chromosome. When phage DNA is excised, flanking bacterial genes may be excised with it. DNA is packaged into phage viral capsid and can infect another bacterium

Question 17

bacterial specialized transduction - genes for the following bacterial toxins are encoded in lysogenic phage

Answer 17

mnemonic: ABCDE
1. shigA-like toxin
2. Botilinum toxin (certain strains)
3. Cholera toxin
4. Diphteria oxin
5. Erytrhogenic toxin of streptococcus pyogenes

Question 18

bacterial specialized vs generalized transduction according to virus

Answer 18

specialized –> lysogenic phase

generalized –> lytic phase

Question 19

F+ x F- vs Hfr x F- conjugation according to transfer

Answer 19

F+ x F- –> transfer single strand of plasmid DNA, no chromosomes
Hfr x F- –> tranfer of plasmid and chromosomal genes