Yeast - What's Happening Here?

[ppacific407]

I have irradiated wild-type yeast with x-rays. They were then grown on agar plates lacking adenine, in hopes of showing the ADE-1 or ADE-2 mutation. I was unsuccessful - There were no red colonies formed. I did three different runs of increasing amounts of radiations. On the third run (which had the highest x-ray doses), the yeast started growing really strangely. I tried to upload a picture, but the upload attachment didn't work, because it said that jpg images can't be uploaded (???) Edited - I added two links to pictures of the yeast cultures
http://rdsindustrial.com/rds/share/ScienceFair/SF.jpg
http://rdsindustrial.com/rds/share/ScienceFair/SF1.jpg

Basically, both of the first runs had nice, round, smooth colonies. This last run has many normal colonies, but several spider-shaped colonies - with fingers radiating outward.

On the internet, I have found references to Filamentous growth of bacteria when they are under stress. Not much specifically on yeast though. Is this a Mutation?

Any help would be appreciated. My conclusions are due this week!

[ppacific407]

I have irradiated wild-type yeast with x-rays. They were then grown on agar plates lacking adenine, in hopes of showing the ADE-1 or ADE-2 mutation. I was unsuccessful - There were no red colonies formed. I did three different runs of increasing amounts of radiations. On the third run (which had the highest x-ray doses), the yeast started growing really strangely.

Links to pictures of the yeast cultures
http://rdsindustrial.com/rds/share/ScienceFair/SF.jpg
http://rdsindustrial.com/rds/share/ScienceFair/SF1.jpg

Basically, both of the first runs had nice, round, smooth colonies. This last run has many normal colonies, but several spider-shaped colonies - with fingers radiating outward.

On the internet, I have found references to Filamentous growth of bacteria when they are under stress. Not much specifically on yeast though. Is this a Mutation?

Any help would be appreciated. My conclusions are due this week!

[deleted-140482]

Hi,

I'm not an expert on yeast growth patterns, so I don't want to tell you something that isn't true. What I will say is this, while it's certainly possible that mutations due to x-ray exposure led to the unusual growth patterns, I don't think it's possible to conclude that definitively. What you can say is that you did not see the mutation you were screening for (i.e. ADE-1 or ADE-2), because if you had, the colonies would be red. Therefore I would conclude that the x-rays did not cause this mutation in your experiment. Then, you can discuss why this might be (i.e. insufficient dose of radiation, other factors), and you can certainly feel free to mention the unusual growth patterns in your yeast that received the highest dose of radiation and hypothesize that this high dose of radiation may have caused other mutations that led to a different growth patterns, but I wouldn't conclude it.

Hope this helps!
JMP

[deleted-132180]

Hello there,

I'm not an expert on yeast growth patterns either, but I think it may be helpful for us if you also have a pictures of WT untreated yeast colonies and the other yeast colonies that have been irradiated with different x-ray doses so we can see the differences between those colonies versus these "weird" colonies from your third run. Have you done some research in the yeast literature to see whether other studies have seen the same unusual morphologies in yeast cells, and what the causes were of those morphologies?

I agree with JMP that since you don't see the mutations you were screening for, the x-rays probably didn't cause this mutation in your experiment. Is there much known about how efficient x-rays are in mutating yeast, and what percentage of the yeast genome is actually mutated upon x-ray treatment? It's interesting if you had done this several times but haven't seen ADE-1 and ADE-2 mutants. While it could be a technical issue, your results may also suggest that these genes are difficult to mutate. Have ADE-1 and ADE-2 mutants been generated in yeast before, and if so, were they done by x-rays or another method? Are these mutants difficult to generate (if they have been made before)? If the mutants are difficult to generate, it may suggest that these genes are important and/or essential for growth and hence will be hard to mutate.

Yeast experts, please correct me if I left anything out or if I mentioned anything incorrectly!

Connie

[ppacific407]

Thanks for your replies.

I have searched all over the web for any similar yeast growth, and have found none. Nothing even close. I have found several versions of this experiment that took place with UV radiation, and they seemed to have no problem getting the ADE-1 and ADE-2 genes to mutate.

I'm a little suspicious that I may have gotten the wrong Agar plates from the Laboratory Supply House that I got them from. I specifically asked for YED (adenine-deficient) plates, but I am wondering if I got YPD plates instead. When they came in, they had no labelling, so I can't be sure. The reason I suspect this, is on my first test, I made my own Agar Plates with a dry mix (which was labeled). I only ran a single plate to try to determine if 10 exposures would kill the yeast. I ran the test, and got a single red (mutated) colony. Then, before I ran the second round (3,6,9,12,15 and 18 exposures) I found a supply house that had pre-made YED Agar plates and ordered those. From then on, I got no red colonies - even though I dramatically increased the exposure doses in round 2 and round 3. It's too late to do the experiment again... so I have to go with what I have.

So, what I'm saying is that it's possible that the ADE-1 or ADE-2 genes are mutated in my experiments, but they may not be evident because there is Adenine in the nutrient. With that in mind, I'm not discounting that mutations have, indeed occurred. This morphological change may or may not be a mutation. I was asking here in hopes that somebody may have a clue as to what this change is.

[ppacific407]

By the way, the pictures that I posted in the link above have both normal, smooth, round colonies and the abnormal ones

[deleted-132180]

Hello there,

If you are suspicious that you had gotten the wrong type of plates, you should probably contact the supplier to see if they have any idea what type of plates they shipped you. If time allows, you should probably repeat your experiment again with plates that you know for sure are the right ones. I do understand that these experiments may take a very long time and your due date may be soon, so in that case, I would just go with your results but probably mention that the plates may be one problem with the strange results you had gotten.

If previous studies have gotten the ADE-1 and ADE-2 mutations before with UV irradiation, then theoretically you should be able to do so as well. Did you treat the yeast cells with UV radiation just as those studies have? Sometimes, small tweaks in the procedures can cause changes in your results, and perhaps those small tweaks may have affected the type of mutants that were generated.

I'm really sorry that I don't really know much about yeast biology because I don't work with yeast. I think if you want a more insightful answer about the strange morphology of some of your cells, you should probably try to contact some labs that are working with yeast via e-mail, send them the pictures, and ask them what they think about it. It could be that certain yeast biologists have also ran into this strange morphology before when they were working with the organism, but that these observations just haven't been published yet. It may also be useful to ask them about your UV irradiation procedure and why you may not have gotten the ADE-1 and ADE-2 mutants.

Hope that helped... Let us know if you have anymore questions!

Best,
Connie