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busutdori
Stranger

Registered: 03/22/16
Posts: 84
Last seen: 7 years, 6 months
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Contaminated agar plates
#23468440 - 07/23/16 07:08 AM (7 years, 7 months ago) |
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Hey shroomerites, On Wednesday I inoculated two agar plates with home made prints. Both of them are contaminated pretty badly. Bacteria slime pretty much everywhere except around the inoculation sites. It looks like the contamination started from the outer edge of the plate and spread inward. Please see the attached pictures. 
What could be the cause for this? Unclean plates? Maybe the saran wrap that I used to seal the plate was loaded with bacteria somehow? I have germinated from spore 4 times before and never had a contamination problem. Right now I am thinking that the new glass petri dish that I've bought are the source of contamination. When they arrived it was pretty obvious from the packaging that the dishes had been opened and then closed. So far I've always bought plastic dishes and I've always used them right out of the packaging. No sterilizing or anything. So I guess my question is, is it possible to sterilize petri dishes in the pressure cooker the same way you sterilize everything else? The dishes are made of glass.
Thank you.
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invitro


Registered: 05/03/13
Posts: 2,529
Last seen: 2 months, 21 days
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Re: Contaminated agar plates [Re: busutdori]
#23477315 - 07/25/16 11:09 PM (7 years, 7 months ago) |
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You can pressure cook the glass ones, not the plastic ones. Cheap plastic is usually polyethylene, which melts at those temps. You might want to google for 'pastyplates'. Glass is kind of a pain IMO.
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Hexus
Insane



Registered: 10/19/15
Posts: 31
Last seen: 7 years, 2 months
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Re: Contaminated agar plates [Re: invitro]
#23477426 - 07/26/16 12:56 AM (7 years, 7 months ago) |
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1/2 pint jars also work well
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busutdori
Stranger

Registered: 03/22/16
Posts: 84
Last seen: 7 years, 6 months
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Re: Contaminated agar plates [Re: Hexus]
#23485257 - 07/28/16 10:33 AM (7 years, 7 months ago) |
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Thanks a bunch. I loved using plastic ones. You are right invitro, glass petris handle very awkward. No need to sterilize too, so convenient. However I am currently in a country where the drug laws are insane. So I thought I'd order glass petris one time and keep reusing them rather than regularly order bunch of plastic petris and throw them out in the trash. Any ideas on where the contamination might have come from though? What usually causes dishes to contaminate like they did in my pics, from edge into the center of the dish? I just sterilized the dishes and inoculated again. Fingers crossed that it'll work this time
Edited by busutdori (07/28/16 10:34 AM)
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