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shymanta
Mad Scientist


Registered: 01/27/05
Posts: 907
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reduce contams on agar
#6537881 - 02/06/07 07:50 PM (17 years, 13 days ago) |
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I thought about posting this in the contamination forum but since I am not dealing directly with a contaminant, I put it mush cult.
I got this idea by accident. Here's what happened.
I had a batch of agar cooling in the PC, waiting to be moved to the glovebox and have H2O2 added, them to be poured. I waited a little too long and the agar was a little thick but still pourable. I added the peroxide and poured anyway. It was fine, just thick. Then I got to the last of the agar. My last dish I only got half full. And because it was thick, it pooled in the middle of the dish.

I didn't think anything of it until the petris had dried. Then I begin thinking that most contamination on agar seems to form on the edge. Eureka! If there is no edge to contaminate? You see the implications. As long as there's no water running around the dish, even if contams get in along the sides, there will be no nutrients for it to land on.
I'm thinking about pouring a batch with all the dishes like this one and see how contamination rates change.
What do you all think?
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Blutjager
Inhuman


Registered: 06/11/06
Posts: 9,220
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Re: reduce contams on agar [Re: shymanta]
#6538090 - 02/06/07 08:43 PM (17 years, 13 days ago) |
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I think if it was that simple it would have been figured out long ago and everyone would be doing it that way already but who knows,maybe your on to something
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RogerRabbit
Bans for Pleasure


Registered: 03/26/03
Posts: 42,214
Loc: Seattle
Last seen: 11 months, 21 days
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Re: reduce contams on agar [Re: Blutjager]
#6538237 - 02/06/07 09:27 PM (17 years, 13 days ago) |
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If you'll wrap your dishes with parafilm, they won't contaminate around the perimeter. RR
-------------------- Download Let's Grow Mushrooms semper in excretia sumus solim profundum variat "I've never had a failed experiment. I've only discovered 10,000 methods which do not work." Thomas Edison
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Hotnuts
old hand


Registered: 02/26/05
Posts: 3,436
Loc: Wild Blue Yawnder
Last seen: 1 month, 12 days
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Re: reduce contams on agar [Re: RogerRabbit]
#6538357 - 02/06/07 10:13 PM (17 years, 13 days ago) |
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I wouldn't rely on that.
You know you can always add the peroxide after the agar has hardened? I do it with all of my live tissue transfers and have NEVER had a contaminate spore or endospore germinate on exposed agar since. I take a small wad of polyfil that's been saturated and rung out with 3% peroxide to apply it on the agar with. Just lightly cover the hard agar and the entire inside of the plate with it. The peroxide will penetrate the hardened agar a bit. Then transfer. Done.
Of course a cotton ball can work as well. But when you ring out a cotton ball, it kind of flattens some. A wad the size of a dry cotton ball of polyfil stays nice a fluffed after being rung out.
Edited by Hotnuts (02/06/07 10:39 PM)
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Workman
1999 Spore War Veteran


Registered: 03/01/01
Posts: 3,598
Loc: Oregon, USA
Last seen: 3 hours, 16 minutes
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Re: reduce contams on agar [Re: shymanta]
#6539855 - 02/07/07 10:33 AM (17 years, 12 days ago) |
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I would expect that a thin pour like that will quickly dry out. It may even separate from the bottom of the dish and freely shift around.
-------------------- Research funded by the patrons of The Spore Works Exotic Spore Supply My Instagram Reinvesting 25% of Sales Towards Basic Research and Species Identification 
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shymanta
Mad Scientist


Registered: 01/27/05
Posts: 907
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Re: reduce contams on agar [Re: Workman]
#6540813 - 02/07/07 03:16 PM (17 years, 12 days ago) |
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Thanks for the input guys!
I always wrap my dishes with para film and have never had any problems with unwanted spores germinating along the edge (at lease not trich). My problems have all been bacterial, I think.
You're probably right, Workman. I think it might shift when dry. But its not that thin because it was clumpy when poured. So it will take a little longer to dry.
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shymanta
Mad Scientist


Registered: 01/27/05
Posts: 907
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Re: reduce contams on agar [Re: Hotnuts]
#6540839 - 02/07/07 03:25 PM (17 years, 12 days ago) |
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Hotnuts, (love the screen name BTW)
I never thought about applying H2O2 after drying. I've got a question for ya, though. You said, "...NEVER had a contaminate spore or endospore germinate on exposed agar..."
What do you mean by exposed? Do you still do your transfers in a glovebox or use HEPA? Or do you transfer in open air? How much attention is paid to sterility?
Much appreciated, Thank!
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