Flashcards in Antibiotic Resistance II Deck (19)
Bacterial uptake of naked DNA from the environment
The ability to take up DNA from the environment
What are the 3 fates for uptake DNA in the cell?
The molecule of DNA introduced into the recipient
Cell's original chromosome
Conjugation involves cell-cell contact, therefore it is sometimes called mating.
The donor cell contains a plasmid. Because all the genes required for conjugation reside on this plasmid, it is called a conjugal plasmid. The recipient does not carry the conjugal plasmid.
How does conjugation occur?
The donor cell harbors an R plasmid; the recipient cell does not. Genes carried by the R plasmid encode a sex pilus, which facilitates capture of the recipient cell to form a mating pair.
Now, a conjugation bridge forms between these two cells through which DNA passes. Transfer of DNA occurs through a special form of replication, called transfer replication. Replication initiates at the origin of transfer (oriT) located on the R plasmid and proceeds by the rolling circle mechanism.
Transduction is form of gene transfer that is mediated by bacterial viruses
Phage binding to a specific receptor on the cell surface
Lytic (virulent) phage cause lysis of the host cell. The phage genome replicates, proteins are synthesized and assembled into capsids, the replicated genomes are packaged within those capsids, the host cell lyses and the progeny escape into the environment to reiterate the process.
Lysogenic (temperate) phage may initiate a lytic growth process or alternatively enter a quiescent form called a prophage. The host cell goes about its business as usual except that it harbors a latent prophage that it passes harmlessly onto its descendents. The cell is capable of becoming lytic at any time though.
What are the two mechanisms where phages can become lysogenic?
-The prophage of certain temperate phage becomes latent by circularizing as an autonomously replicating plasmid.
-The prophage of other temperate phage becomes latent by physically integrating into the host chromosome.
Does conjugation require cell to cell contact?
Does transduction require cell to cell contact?
Can nucleases disrupt transformation?
Can nucleases disrupt transduction?
No as the phage head protects the DNA
What are some of the clinical problems that arise with gene exchange?
Antibiotic preparations themselves are often contaminated with DNA that encodes resistance genes. This contamination thus increases the chance of genetic exchange via transformation between antibiotic-producing organisms and the pathogens they are being used to control.
Factors that may affect efficient transformation
C. Cell competence
D. None of the above
E. All of the above
E. All of the above