Conjugation, transduction, transformation

Transformation is when a bacterial cell picks up free DNA fragments/genes directly from the extracellular medium.

Bacteria that are capable of transformation are known as “competent.” S. pneumo is known as a natural transformer, and is therefore competent.

The highest yield point for USMLE is that transformation can be disrupted when DNase is added to the surrounding medium. This is because it will break down any free DNA fragments/genes that are floating around and exposed.

The USMLE will ask something like, “Which of the following observations by a researcher most likely supports transformation as the mechanism for antibiotics resistance gene transfer?” The answer will be something like, “Process is disrupted with addition of nucleotidase.”

Or they can say, “A researcher is conducting an experiment regarding bacterial antibiotics gene transfer. It is observed that the process is disrupted by the addition of DNase. What is the most likely mechanism of gene transfer?” Answer = transformation.

Answer can be something like “Genes traced to locus adjacent viral excision site.”

Specialized transduction is when a viral (phage) particle enters a bacterial cell, lysogenically incorporates itself into the bacterial’s DNA genome, then reemerges with flanking bacterial DNA sequences which are then packaged into new phage particles. These new phage particles then infect other bacterial cells and transfer these flanked genes.

The reason this type of transduction is called specialized is because the transferred bacterial DNA isn’t random; it is specific to the site on the bacterium’s genome where the virus incorporates itself, which in some cases can predictably be genes encoding toxins or antibiotics resistance.

In comparison to generalized transduction, you can see that in specialized, once the virus enters the cell, it’s nucleic acid becomes integrates lysogenically within the bacterium’s. Upon reemergence, we now have viral nucleic acid with flanking bacterial sequences.

The USMLE could ask which of the following observations by a researcher about transferred bacterial genes would support specialized transduction as the mechanism. The answer will be something like, “Genes traced to locus adjacent viral excision site.” Wording can seem a bit recondite, but it’s not hard now that we discussed it.

Antibiotics resistance genes are transferred from one bacterium to another via a tube called a pilus. 

“Loss of plasmid.”

A HY general principle you need to know is that most bacteria carry their antibiotics resistance genes on a plasmid, rather than in their chromosomal DNA. A plasmid is a small, circular, dsDNA molecule that is separate from a bacterium’s chromosomal DNA and can replicate independently.

The USMLE will ask something like, “A bacterial colony that is observed to replicate over many generations loses its resistance to vancomycin. Which of the following mechanisms is the most likely explanation for this finding?” And the answer is just “loss of plasmid.” Not complicated. But if you don’t know the factoid about antibiotics resistance genes normally being carried on the plasmid, you’d be like what the fuck?

Conjugation. This is when genes (often for antibiotics resistance) are transferred from one bacterium to another via a tube called a pilus. 

Transformation is when a bacterial cell picks up free DNA fragments/genes directly from the extracellular medium.

Bacteria that are capable of transformation are known as “competent.” S. pneumo is known as a natural transformer, and is therefore competent.

The highest yield point for USMLE is that transformation can be disrupted when DNase is added to the surrounding medium. This is because it will break down any free DNA fragments/genes that are floating around and exposed.

The USMLE will ask something like, “Which of the following observations by a researcher most likely supports transformation as the mechanism for antibiotics resistance gene transfer?” The answer will be something like, “Process is disrupted with addition of nucleotidase.”

Or they can say, “A researcher is conducting an experiment regarding bacterial antibiotics gene transfer. It is observed that the process is disrupted by the addition of DNase. What is the most likely mechanism of gene transfer?” Answer = transformation.

Transformation is when a bacterial cell picks up free DNA fragments/genes directly from the extracellular medium.

Specialized transduction is when a viral (phage) particle enters a bacterial cell, lysogenically incorporates itself into the bacterial’s DNA genome, then reemerges with flanking bacterial DNA sequences which are then packaged into new phage particles. These new phage particles then infect other bacterial cells and transfer these flanked genes.

The reason this type of transduction is called specialized is because the transferred bacterial DNA isn’t random; it is specific to the site on the bacterium’s genome where the virus incorporates itself, which in some cases can predictably be genes encoding toxins or antibiotics resistance.

In comparison to generalized transduction, you can see that in specialized, once the virus enters the cell, it’s nucleic acid becomes integrates lysogenically within the bacterium’s. Upon reemergence, we now have viral nucleic acid with flanking bacterial sequences.

The USMLE could ask which of the following observations by a researcher about transferred bacterial genes would support specialized transduction as the mechanism for gene transfer. The answer will be something like, “Genes traced to locus adjacent viral excision site.” Wording can seem a bit recondite, but it’s not hard now that we discussed it.

Transduction refers to a phage (viral) particle transferring genes from one bacterium to another.

The way the USMLE will ask this is they will say something like, “A researcher is conducting an experiment about antibiotics gene transfer. Which of the following observations would best support the conclusion that conjugation is the method of transfer?” Then the answer is, “direct cell to cell contact.” In other words, the tube/pilus that connects the two bacterium necessitates cell-to-cell contact.

Lysogeny refers to the ability of some viruses to incorporate themselves into the nucleic acid of the host and then reemerge later.

During the process of generalized transduction, the phage particle does not incorporate itself into the bacterial genome when it packages up DNA. In other words, there is no lysogenic process (lysogeny) as part of the process.

Specialized transduction is when a viral (phage) particle enters a bacterial cell, lysogenically incorporates itself into the bacterial’s DNA genome, then reemerges with flanking bacterial DNA sequences which are then packaged into new phage particles. These new phage particles then infect other bacterial cells and transfer these flanked genes.

The reason this type of transduction is called specialized is because the transferred bacterial DNA isn’t random; it is specific to the site on the bacterium’s genome where the virus incorporates itself, which in some cases can predictably be genes encoding toxins or antibiotics resistance.

Transformation is when a bacterial cell picks up free DNA fragments/genes directly from the extracellular medium.

Bacteria that are capable of transformation are known as “competent.” S. pneumo is known as a natural transformer, and is therefore competent.

The highest yield point for USMLE is that transformation can be disrupted when DNase is added to the surrounding medium. This is because it will break down any free DNA fragments/genes that are floating around and exposed.

The USMLE will ask something like, “Which of the following observations by a researcher most likely supports transformation as the mechanism for antibiotics resistance gene transfer?” The answer will be something like, “Process is disrupted with addition of nucleotidase.”

Generalized transduction is when a phage particle enters a bacterial cell, packages up random fragments from the bacterium’s DNA genome within its new phage particles, then leaves the cell, infecting a new bacterium and spreading these genes as a result.

During the process of generalized transduction, the phage particle does not incorporate itself into the bacterial genome when it packages up DNA. In other words, there is no lysogenic process (lysogeny) as part of the process. Lysogeny refers to the ability of some viruses to incorporate themselves into the nucleic acid of the host and then reemerge later.

Transduction refers to a phage (viral) particle transferring genes from one bacterium to another.

A HY general principle you need to know is that most bacteria carry their antibiotics resistance genes on a plasmid, rather than in their chromosomal DNA. A plasmid is a small, circular, dsDNA molecule that is separate from a bacterium’s chromosomal DNA and can replicate independently.

The USMLE will ask something like, “A bacterial colony that is observed to replicate over many generations loses its resistance to vancomycin. Which of the following mechanisms is the most likely explanation for this finding?” And the answer is just “loss of plasmid.” Not complicated. But if you don’t know the factoid about antibiotics resistance genes normally being carried on the plasmid, you’d be like what the fuck?

Answer can be something like, “Non-lysogenic phage particles present.”

Generalized transduction is when a phage particle enters a bacterial cell, packages up random fragments from the bacterium’s DNA genome within its new phage particles, then leaves the cell, infecting a new bacterium and spreading these genes as a result.

During the process of generalized transduction, the phage particle does not incorporate itself into the bacterial genome when it packages up DNA. In other words, there is no lysogenic process (lysogeny) as part of the process. Lysogeny refers to the ability of some viruses to incorporate themselves into the nucleic acid of the host and then reemerge later.

USMLE Qs on this topic are fairly straightforward. They might say something like, “Which of the following observations by a researcher supports generalized transduction as the mechanism for antibiotics gene transfer?” And the answer will be something like, “Non-lysogenic phage particles present.” The answer on its own can sound cryptic/arcane, but now that we discussed it, it’s not so bad.

Specialized transduction is when a viral (phage) particle enters a bacterial cell, lysogenically incorporates itself into the bacterial’s DNA genome, then reemerges with flanking bacterial DNA sequences which are then packaged into new phage particles. These new phage particles then infect other bacterial cells and transfer these flanked genes.

The reason this type of transduction is called specialized is because the transferred bacterial DNA isn’t random; it is specific to the site on the bacterium’s genome where the virus incorporates itself, which in some cases can predictably be genes encoding toxins or antibiotics resistance.

In comparison to generalized transduction, you can see that in specialized, once the virus enters the cell, it’s nucleic acid becomes integrates lysogenically within the bacterium’s. Upon reemergence, we now have viral nucleic acid with flanking bacterial sequences.

The USMLE could ask which of the following observations by a researcher about transferred bacterial genes would support specialized transduction as the mechanism for gene transfer. The answer will be something like, “Genes traced to locus adjacent viral excision site.” Wording can seem a bit recondite, but it’s not hard now that we discussed it.