Difficult Genetics Problem

[mystic river 00]

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Ok, after hours upon hours of trying to figure this darn thing out...I've given up and decided to rely on my fellow SDNers! Get ready, here it is..........

The Problem:

" You set up an experiment with two strains of genetically different basteria in a U-tube. The filter between the 2-sides is too small to allow physical contact between the bacteria. The solution has been purified of bacteria. After a time, you notice that some strain B cells have acquired some genetic characteristics of Strain A. Explain what is happening"

My thoughts:

I was thinking it was the same situation as Bernad Davis'.... "He constructed a U-tube in which the two arms were separated by a fine filter. The pores of the filter were too small to allow bacteria to pass through but large enough to allow easy passage of the fluid medium and any dissolved substances ( Figure 7-3). Strain A was put in one arm; strain B in the other. After the strains had been incubated for a while, Davis tested the content of each arm to see if cells had become able to grow on a minimal medium, and none were found. In other words, physical contact between the two strains was needed for wild-type cells to form."


so, I thought it was transformation but they need physical contact, and in this case, they don't. You obviously have to have exchange of DNA somehow, but I just don't know how?!!! ... how can it do that without viruses or physical contact??? In that case, the answer can't be conjugation, transformation, nor transduction, right?!!



AHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!


:::::::Runs away::::::::::





Ok, enough with this, I'm going to sleep...

 

[jpro]

Isn't transformation when DNA is taken up by the bacteria through receptors on the cell membrane. DNA is just floating around probably from cell death (lysis) releasing the DNA from the bacteria allowing interaction.

I'm no biochem/genetic buff, but that is how I understand it.

 

[King Arthur]

what does "physical contact" mean? if it means that bacteria can't cross, you could still have genetic material from a dead bug get to the other side.

 

[omarsaleh66]

I think the physical contact is referring to the fact that conjugation cannot take place. However, i bet u that DNA can pass thru the pores so there is transformation goin on.

 

[Giving My .02]

My guess... plasmids (However, I don't know about the filter & contact)

 

[peterson]

im not 100%, but theres a classic genetics experiment (maybe Griffith's??) where DNA from dead virulent bacteria transformed normal bacteria to virulent showing genetic material was in fact DNA. so maybe its DNA that transferred over and transformed the bacteria. my guess.

Ok, after hours upon hours of trying to figure this darn thing out...I've given up and decided to rely on my fellow SDNers! Get ready, here it is..........

The Problem:

" You set up an experiment with two strains of genetically different basteria in a U-tube. The filter between the 2-sides is too small to allow physical contact between the bacteria. The solution has been purified of bacteria. After a time, you notice that some strain B cells have acquired some genetic characteristics of Strain A. Explain what is happening"

My thoughts:

I was thinking it was the same situation as Bernad Davis'.... "He constructed a U-tube in which the two arms were separated by a fine filter. The pores of the filter were too small to allow bacteria to pass through but large enough to allow easy passage of the fluid medium and any dissolved substances ( Figure 7-3). Strain A was put in one arm; strain B in the other. After the strains had been incubated for a while, Davis tested the content of each arm to see if cells had become able to grow on a minimal medium, and none were found. In other words, physical contact between the two strains was needed for wild-type cells to form."


so, I thought it was transformation but they need physical contact, and in this case, they don't. You obviously have to have exchange of DNA somehow, but I just don't know how?!!! ... how can it do that without viruses or physical contact??? In that case, the answer can't be conjugation, transformation, nor transduction, right?!!



AHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!


:::::::Runs away::::::::::





Ok, enough with this, I'm going to sleep...

 

[4ruralhealth]

Ok, after hours upon hours of trying to figure this darn thing out...I've given up and decided to rely on my fellow SDNers! Get ready, here it is..........

The Problem:

" You set up an experiment with two strains of genetically different basteria in a U-tube. The filter between the 2-sides is too small to allow physical contact between the bacteria. The solution has been purified of bacteria. After a time, you notice that some strain B cells have acquired some genetic characteristics of Strain A. Explain what is happening"

My thoughts:

I was thinking it was the same situation as Bernad Davis'.... "He constructed a U-tube in which the two arms were separated by a fine filter. The pores of the filter were too small to allow bacteria to pass through but large enough to allow easy passage of the fluid medium and any dissolved substances ( Figure 7-3). Strain A was put in one arm; strain B in the other. After the strains had been incubated for a while, Davis tested the content of each arm to see if cells had become able to grow on a minimal medium, and none were found. In other words, physical contact between the two strains was needed for wild-type cells to form."


so, I thought it was transformation but they need physical contact, and in this case, they don't. You obviously have to have exchange of DNA somehow, but I just don't know how?!!! ... how can it do that without viruses or physical contact??? In that case, the answer can't be conjugation, transformation, nor transduction, right?!!



AHHHHHHHHHHHHHHHHHHHH!!!!!!!!!!


:::::::Runs away::::::::::






Ok, enough with this, I'm going to sleep...

I think that most likely this is a case of transduction or transfer of DNA from on bacterial host to the other using a viral vector such as a bacteriophage. The viruses are certainly small enough to pass between the filter paper and do not require cell to cell contact (at least between the bacteria any way).

Another possibility is this but less likely: Certain bacteria are capable of taking up free DNA from their environments if the conditions are right (typically fluctuations of temperature, electrostatic, and chemical forces) The first is the basis of making bacteria "competent" via the "heat sock" methodology used extensively in molecular biology. Whether it is integrated into the host genome is another story, but in this case it appears that it has. Typically the DNA is in the form of "plasmid DNA" which should be able to pass through the medium separating the microbes. In fact, uptake and transfer of DNA into specially engineered plasmids (selectable markers and restriction enzyme sites) is the basis of "Molecular Cloning". Hope this helps.