Plasmids, conjugation, and transformation III

What is another type of partitioning system?

sok and hok

What is hok?

It encodes a protein that is toxic to the host (host killing)

What does sok make?

It makes an antisense RNA that prevents hok translation (suppressor of killing)

What happens if plasmid is lost?

Hok is made and the cell dies

If you express many genes from a large gene is it a burden if the genes are not required? Is there selection pressure to lose the plasmid?

Yes to both

Are all features of a plasmid always required? Is there a selection pressure? Why? What would happen if the selection pressure disappeared?

No and yes there is because plasmid comes at a cost. Plasmid would probably be lost

Does the environment context matter for whether a plasmid is kept or not? What is a good example?

Yes it is and an example is facultative pathogens

How big is the shigella virulence plasmid?

200 Kb

Is there high expression of the shigella virulence plasmid genes at 37 degrees?

Yes there is

When is the shigella virulence plasmid lost?

If virulence is not required (in lab grown media)

Do some plasmids encode antibiotic resistance?

Yes

Why might you keep a plasmid?

If an antibiotic is around and you have antibiotic resistance genes on the plasmid

Can plasmids be high or low copy number?

Both

What are three mechanisms that exist to ensure plasmid propagation?

1. Specialized replication mechanisms

2. Partitioning systems that kill host if they do not inherit plasmid

3. Ways of getting rid of other plasmids (incompatibility)

Do plasmids always get along?

No and this is why we have plasmid incompatibility because the plasmid in a cell can combat others from coming in

Are plasmids in the lab unstable? Can they be lost and rearrange? Are they useful in the lab? What can they be used for?

Yes to all. Can be used for recombinant DNA

What is transformation? Can plasmids be moved around this way?

It is the uptake of naked (uncomplexed) DNA and yes

What did Griffiths experiment use? What did it show?

Transformation to show that DNA was the genetic material

What is complexed DNA?

It is when proteins are bound to DNA or it is in a nucleoidor nucleus

What did Griffith use? What encodes the protein coats? What did his experiment show?

Rough and smooth strains (refers to the protein coat) of streptococcus. Genetic material. Genetic material was being exchanged when both strains were mixed that caused the rough strain to turn smooth sometimes and smooth strain could turn rough

Are some strains naturally competent to take up DNA?

Yes

Can cells be made chemically competent? How?

Yes through salt and buffers

What are two desperate ways to transform DNA?

1. Bolistic transformation

2. Electroporation

What is bolistic transformation?

It is when you take a pellet gun and load DNA onto gold particles and shoot the gun and it pierces into cells

What is electroporation?

You can shock the DNA to force the DNA by electric current into the cell using a capacitor

What is a con of transformation?

DNA may encode things that are not beneficial

Why is it difficult to get DNA into bacteria?

This is because you spend so much time getting everything perfect and maintaining the blueprint of life that you don’t want foreign DNA to be able to get in easily and mess everything up. They have mechanisms to prevent this.

What is a benefit of foreign DNA?

It can help you repair DNA

What are competent bacteria?

They can take up DNA from the environment

What phase have naturally competent bacteria become competent in response to?

Growth phase (usually late log phase)

What can competence be linked to?

Diffusible factors (quorum sensing)

What do competent bacterial cells have? What are some examples?

Proteins that bind preferred DNA sequences usually from a related or the same species. Neiseeria and haemophilus spp.

What do naturally competent bacteria have dedicated structures and systems for? Why?

Uptake of DNA because they have a membrane that is difficult for nucleotides to get across

What does DNA enter as? What needs to happen? How?

ssDNA and needs to be turned into dsDNA. Can be done through adding a primer and ssDNA acting as a template or through recombination.