32 Transformation

Question

Answer

What is bacterial transformation?

Direct uptake of DNA from the environment into a bacterium.

What does competent mean?

Able to take up extracellular DNA.

Can starvation promote competence?

Yes, stress such as starvation can induce competence in some species.

What is a competence factor?

A signaling molecule that promotes competence in certain bacteria, including some Gram-positive species.

What is a translocasome?

A cell-envelope complex involved in taking up extracellular DNA.

Does transformation require direct donor–recipient contact?

No; DNA can come from the surrounding environment.

What happened when Griffith mixed heat-killed virulent S bacteria with living nonvirulent R bacteria?

Mice died and living virulent S bacteria could be recovered.

What did Griffith’s experiment demonstrate?

A heritable transforming principle from dead bacteria could change living bacteria.

What provides the DNA for natural transformation?

Free DNA released into the environment, often from dead or lysed cells.

How can a transformed cell retain a new trait?

The acquired DNA must be maintained, such as by recombination or plasmid replication.

How is laboratory transformation useful?

It introduces recombinant plasmids into bacteria for cloning and expression.

What is positive selection after plasmid transformation?

Growth conditions permit plasmid-containing cells to survive while nontransformants do not.