Bacterial genetics Flashcards
Bacterial genetics - transformation / aka
Ability to take up naked DNA (from cell lysis) from environment / AKA competence
transformation (competence) - which bacteria?
many bacteria –> especially S. pneumoniae, H. influenzae type B, Neisseria
transformation (competence) - which DNA is used
any DNA can be used
how to avoid transformation in medium
add deoxyribonuclease to environment –> to degrade naked DNA
bacterial Conjunction - types
- F+ x F-
2. Hfr x F-
F+ bacteria vs F- bacteria?
F+: bacterial with plasmid contains genes required for sex pilus and conjugation
F-: bacterial without plasmid contains genes required for sex pilus and conjugation
F+ x F- conjunction?
sex pilus on F+ bacterium contacts F- bacterium. A SINGLE strand of plasmid DNA is transferred across the conjugal bridge (aka the mating bridge)
F+ x F- conjunction - what is transferred and what is not transferred
A SINGLE strand of plasmid DNA is transferred
NO TRANFER OF CHROMOSOMAL DNA
F+ x F- conjunction - transfer across
the conjugal bridge (aka the mating bridge)
Hfr bacteria?
F+ plasmid can become incorporated into bacterial chromosomal DNA, termed high-frequency recombination (Hfr) cell
Hfr x F- conjugation?
replication of incorporated DNA may include some flaking chromosomal DNA –> transfer of plasmid and chromosomal
bacterial transposition?
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
tranfer of a gene from a bacterium to another bacterium through transposition (examples)
vanA gene from vancomycin-resistant Enterococcus to S. aureus
bacterial transduction - types
- Generalized
2. Specialized
bacterial generelized transduction?
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
bacterial specialized transduction?
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
bacterial specialized transduction - genes for the following bacterial toxins are encoded in lysogenic phage
mnemonic: ABCDE
1. shigA-like toxin
2. Botilinum toxin (certain strains)
3. Cholera toxin
4. Diphteria oxin
5. Erytrhogenic toxin of streptococcus pyogenes
bacterial specialized vs generalized transduction according to virus
specialized –> lysogenic phase
generalized –> lytic phase
F+ x F- vs Hfr x F- conjugation according to transfer
F+ x F- –> transfer single strand of plasmid DNA, no chromosomes
Hfr x F- –> tranfer of plasmid and chromosomal genes
