Agar Plates

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AnnNos
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Agar Plates

Post by AnnNos »

I've been making nutrient agar plates for years with very good growth of bacteria of all sorts using agar that was in my store.

However, I purchased new nutrient agar 6 months ago and now the vast majority of the plates hardly grow anything. :cry2: My technique hasn't changed. Is anyone else having this problem? The bottles I bought aren't cheap but if it doesn't grow anything it's useless.
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Labbie
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Re: Agar Plates

Post by Labbie »

I have had trouble with Agar 1000 gel powed, but never the Nutrient agar, where did you purchase it from?
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AnnNos
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Re: Agar Plates

Post by AnnNos »

Serrata
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Labbie
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Re: Agar Plates

Post by Labbie »

Ring them, the supplier may do a refund.
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bigmack
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Re: Agar Plates

Post by bigmack »

I read that you should store Agar plates upside down after making them .
I fail to understand the logic in this .
Can anyone explain why ...I must be missing something .
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Labbie
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Re: Agar Plates

Post by Labbie »

so the lids stay dry, no condensation.
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Shell1
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Re: Agar Plates

Post by Shell1 »

Try southern biological, never had an issue with their agar (plain agar powder). Recipe I use is 10g bonox (beef extract), 10g peptone, 5g NaCl, 15g agar powder, 1L distilled water. Never had any issues with the supplier or this recipe.
Agar plates should always be stored and incubated upside down to prevent growth from condensation
Merilyn1
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Re: Agar Plates

Post by Merilyn1 »

They're stored upside down to prevent condensation settling on the agar.
bigmack
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Re: Agar Plates

Post by bigmack »

Thanks Labbie and shell .
when I make them and they are setting , condensation forms on the lids . I tip them upside down and store in fridge , next day there are obvious pools on some of the agar plates but not all :-? and there is some condensation on the inverted lids . I find it a bit hit and miss still .

So is the theory that the condensation can escape up the gap between the lid and base ? I was concerned thinking that "stuff" could fall back down into them :oops:
Shell1
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Re: Agar Plates

Post by Shell1 »

Once the agar has set I turn them upside down and place them back into the bag the original agar plates came in and seal the bag with some tape before putting into fridge. I only seem to get condensation within the bag and not the plates. Hope this helps
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Lyn
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Re: Agar Plates

Post by Lyn »

Same here. Once plates are set I pop them into ziplock sandwich bags (about five plates to a bag) and store them upside down in the fridge.
Prima
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Re: Agar Plates

Post by Prima »

What a great idea, Shell1 and Lyn - can't wait to try it, makes the plates so much easier to handle, too!
DavidM
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Re: Agar Plates

Post by DavidM »

Kanamycin sulfate for Kanamycin agar plates. Does any-one know how long Kanamycin Sulfate solution (34mg/ml) can be stored and whether it should be stored at 4C or -20C?
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Labbie
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Re: Agar Plates

Post by Labbie »

Kanamycin monosulfate
from Streptomyces kanamyceticus
Product Number K0879
Storage Temperature 2-8 °C
Product Description
Molecular Formula: C18H36N4O11 · H2SO4
Molecular Weight: 582.6
CAS Number: 25389-94-0
This product is g-irradiated and is recommended for
use in molecular biology applications at 10-50 mg/ml.
Kanamycin sulfate is an antimicrobial agent effective
against Gram-negative and Gram-positive bacteria
and mycoplasma. It binds to the 70S ribosomal
subunit, inhibits translocation, and elicits miscoding.
Cross-resistance occurs between kanamycin and
neomycin, framycetin, and paromomycin, and partial
cross-resistance has been reported between
kanamycin and streptomycin.1
Aminoglycosidemodifying
enzymes (acetyltransferase,
phosphotransferase, nucleotidyltransferase) alter the
antibiotic, preventing its interaction with ribosomes.
Kanamycin sulfate can be added into agar (agar
plate), and the plate should be then be sealed to
prevent any evaporation of moisture from the agar.
The sealed plate can be stored at 2-8 °C for about one
month. If the plate is not sealed to prevent
evaporation of moisture, the kanamycin can degrade.
Precautions and Disclaimer
For Laboratory Use Only. Not for drug, household or
other uses.
Preparation Instructions
Prepare stock solutions directly in the vial with sterile
water (10 mg/ml).
Kanamycin sulfate is soluble in water (50 mg/ml),
yielding a clear solution. Kanamycin sulfate is
practically insoluble in alcohol, acetone, chloroform,
ether, and ethyl acetate. A 1% solution in water has a
pH of 6.5 to 8.5. This is in contrast to the pH of 5.5 to
7.5 for a 1% solution in water of kanamycin acid
sulfate.1
Storage/Stability
Sterile solutions can be prepared by sterile filtration
through a 0.2 mm filter. Solutions are stable at 37 °C
for approximately 5 days. Aqueous stock solutions
can be stored at 2-8 °C for long term storage.
References
1. Martindale The Extra Pharmacopoeia, 31st ed.,
Reynolds, J. E. F., ed., Royal Pharmaceutical
Society (London, England: 1996), p. 244.
JSX/ARO/HLD/RXR 5/06
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DavidM
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Re: Agar Plates

Post by DavidM »

Thanks Labbie for the information on Kanamycin. DavidM
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Re: Agar Plates

Post by DavidM »

Shell1 I was interested in the Agar you recommended as it is much cheaper than what we buy from Sigma. Do you mind telling me what you grow on your agar plates. It may be suitable for us and save us a lot of money.
mtg
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setting agar-agar

Post by mtg »

How much agar-agar per 100ml does it take to set it. I have a prac for 1.5% agar-agar and I don't think it will be strong enough.
Merilyn1
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Re: Agar Plates

Post by Merilyn1 »

Off the top of my head, I think it's about 15g per litre of water, so not sure what you'll end up with only 1.5%.

And David, going back to your post from October (which I had missed), the recipe Shell has given you will make something similar to nutrient agar, so broad use. Without the agar, it also makes a great nutrient broth. Yes, it is cheaper, but is a bit more time consuming, so you need to weigh up your material costs against the time it will take to make. When I was making a lot of plates, and had the time, I would use this recipe for the junior classes, and save the purchased nutrient agar for the seniors - although they both worked pretty well.
Merilyn1
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Re: Agar Plates

Post by Merilyn1 »

Oh, so wrong - 28g per litre is the amount for the nutrient agar I have.
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Labbie
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Re: Agar Plates

Post by Labbie »

I have bumped this to the top, as there are some great reads, regarding making agar for us all
Regards Labbie

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Now retired :wub:
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