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Psilosopherr
A psilly goose



Registered: 02/15/12
Posts: 12,278
Last seen: 1 month, 10 days
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Unopened petri dishes all contamed
#22409194 - 10/20/15 12:49 PM (8 years, 3 months ago) |
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So I use wide mouth half pints as petri's. Just cooked some MEA in them for 45 minutes the other day, went to use them and noticed they all had condensation in the center of the agar.
Several of them even had this weird contam I've seen once before. Its like a clear jellyfish substance with lines forming a pattern within it. Hopefully someone can ID it from the picture. It'd be nice to learn more about the organisms that cause this so that I can better know how to avoid it. pics below
As for what went wrong: I've recently started using unmodified plastic lids. Some say they don't form a perfect seal, that may explain the contams. But what about the condensation itself? I was using some agar that had clumped up due to being improperly sealed, perhaps the moisture content was too high and hence some extra water separated from the agar and pooled in the middle?
the lids were also loose after PC'ing...and I didn't use foil because they have no filters...Oh shit was that it? 
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Psilosopherr
A psilly goose



Registered: 02/15/12
Posts: 12,278
Last seen: 1 month, 10 days
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Re: Unopened petri dishes all contamed [Re: Psilosopherr]
#22419246 - 10/22/15 05:29 PM (8 years, 3 months ago) |
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so I used my tried and true PDA with metal lids and this still happened on 3/4 jars. All of the jars it happened to were able to be tightened slightly more...I wouldn't think it would be enough for liquid to get through but that must be whats happening.
all the ones that get this weird contam have extra water on top of the agar layer. Its almost like its a condensation problem because I never notice extra water in there right after the PC cycle.
Or maybe extra water seeps in during the PC cycle, and mixes in well enough that it doesn't re-separate for a while. 
Maybe I should use foil on the lids even though there's no ports/filters to protect from water??
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cronicr



Registered: 08/07/11
Posts: 61,436
Loc: Van Isle
Last seen: 2 years, 8 days
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Re: Unopened petri dishes all contamed [Re: Psilosopherr]
#22419293 - 10/22/15 05:37 PM (8 years, 3 months ago) |
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i would go back to your metal lids with a filter
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  It doesn't matter what i think of you...all that matters is clean spawn I'm tired do me a favor
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Psilosopherr
A psilly goose



Registered: 02/15/12
Posts: 12,278
Last seen: 1 month, 10 days
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Re: Unopened petri dishes all contamed [Re: cronicr]
#22419312 - 10/22/15 05:40 PM (8 years, 3 months ago) |
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damn, you think its that the containers are totally closed?
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Kizzle
Misanthrope


Registered: 08/30/11
Posts: 9,855
Last seen: 16 hours, 32 minutes
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Re: Unopened petri dishes all contamed [Re: Psilosopherr]
#22420985 - 10/22/15 11:45 PM (8 years, 3 months ago) |
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If there's no filter, unfiltered air can get pulled in when the pressure equalizes after sterilization so maybe.
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Psilosopherr
A psilly goose



Registered: 02/15/12
Posts: 12,278
Last seen: 1 month, 10 days
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Re: Unopened petri dishes all contamed [Re: Kizzle]
#22420995 - 10/22/15 11:48 PM (8 years, 3 months ago) |
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thanks!
Hopefully plastic lids will still work if I add filters. I have about 50/50 metal/plastic lids right now but I really like plastic mainly because they are one piece.
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Psilosopherr
A psilly goose



Registered: 02/15/12
Posts: 12,278
Last seen: 1 month, 10 days
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Re: Unopened petri dishes all contamed [Re: Psilosopherr]
#22422552 - 10/23/15 11:30 AM (8 years, 3 months ago) |
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Any idea what contam I got specifically? or is it just "bacteria" in general?
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cronicr



Registered: 08/07/11
Posts: 61,436
Loc: Van Isle
Last seen: 2 years, 8 days
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Re: Unopened petri dishes all contamed [Re: Psilosopherr]
#22422981 - 10/23/15 01:26 PM (8 years, 3 months ago) |
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i havent' used plastic lids for my no pours in a long time but i know with glass and metal lids i get no condensation, sometimes i get a littel excess water on top but that goes away in a couple of days
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  It doesn't matter what i think of you...all that matters is clean spawn I'm tired do me a favor
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