Nutrient agar plates

[Sharls]

I need to make some nutrient agar and cannot find a decent recipe. I have some Agar 750 gel powder do I just use this or add something else, like bonox or vegemite?

Sharls

[Slartibartfast]

If you do a search Sharlene under 'agar', quite a lot has been discussed on this forum and there are some really effective recipes to boot!

[Sharls]

Thanks Richard I will do that. I am still trying to find my way around this site, I don't know how to use it to it fullest potential yet.

Sharls

[lada]

Hi,
You can use nutrient agar (from Serrata or Southern Biological), but if you have only plain agar, you will have to add vegemite or bonox.
I normally make 3%agar (3g in 100ml of water), heat it to dissolve, add teaspoon of vegemite per 1L and autoclave it.
You can also add 5-10g of peptone
Good luck
Lada

[Sharls]

Thanks Lada that was just what I needed.
Sharls

[Ian]

This is the recipe that I use. It seems to work well.

Dissolve in 1L of distilled water, on a hotplate
Peptone, 5g
NaCl, 5g
Vegemite, 2g
Bonox, 1g

When dissolved and hot (not boiling) add 15g Agar powder, dissolve. Pour into 250ml flasks, stopper wigh cotton wool and alfoil. Autoclave for 15min's

I find that I can get about 10 plates out of one 250ml flask, so I generally make up half the above quantity and that does for a packet of 20 plates

Cheers
Ian

[lada]

Yes, I would use Ian's recipe. I think NaCl makes a better growing medium.
Lada

[Lis]

Do you know what to use if you have no autoclave, or pressure cooker, though I do have a microwave, is it ok to kill them in the microwave before disposing of them?, if so how long do you think?

cheers Lisa

[Labbie]

Lisa, please check agar plates from before, I now use Microwave after reading all about it on chemtalk. But as for the time, I am not too sure.

[Sharls]

Great recipe Ian thankyou! You also answered my next question, how long do I autoclave for. Is it alright to store unused agar in fridge and reheat to use at a later date?

Sharls

[SGG]

Hi Sharls
I usually put all the warm agar into petri dishes. Any that aren't to be used straight away I wrap in plastic (as a group) and store in the fridge. If you watch your sterility when first pouring, they can last for weeks. I have never tried reheating nutrient agar - only phenolphthalein agar when I hadn't added enough agar to get it to set!
Regards
Sue G

[kimm]

Hey Sharls
I keep my unopened sterilized flasks of nutrient agar in the fridge - i never have a problem with it. Once I have opened the flasks I do not try to store it again due to contamination risks.
cheers
kimm

[lizzieb]

We've just been discussing the cost of agar these days, and whether gelatine could be used as a substitute for agar when making up agar plates. I thought I remembered someone giving a recipe recently. My HT has heard of lemon jelly being used, another teacher used gelatine in a private industry situation.

Does anyone have any more info or ideas?

I did a search, and came up with Jazz's entry for phenolphthalein blocks back in February, which used gelatine.
At the very least it would be fun to experiment and see what could be done!

[dolphinscales]

Has anyone used the petrifilm plates? From Southern Biological?

as we do not do many plates we were thinking maybe to going to using them. That way we ahve more control over what the kids "sample". still teachers here that let them wonder around and to toilets and such like.

[rell]

We have some wonderful growths on our agar plates. Problem is i dont know what they are. Can someone help me please?

Narelle Divola
Irymple Secondary College

[smiley]

After growing greeblies on our agar plates, I made an appointment with the local pathology labs and spent some time with the lab techs there. They were able to ID in an instant all the various bizzos growing there. I mean, it's what they do all day long, so why bother trying to guess.

Our kids grew a nice little culture from the sick bay pillow cases, so we took those plates to the lab techs. They were able to point out that if the only germs found on the sick bay pillow case were a few of the natural human skin flora, that acts as the body's defence mechanism, then it was essentially a CLEAN pillowcase. Which is nice to know, I'm sure.

So see if you can find someone like that. Ours are very helpful, above and beyond really.

[Tim]

In regards to sterilizing plates after incubation, if you don't have access to an autoclave (pressure cooker), you can sterilize them with Chlorine bleach, though I don't like to. You can also "Tyndalize" (I think that's how it is spelled) them. Place them in a container and boil them for 10mins. keep the container sealed and boil them again after 2 days. Again keep them in the container for 2 days and boil them for a third time. The theory is that the first boiling kills all vegetative cells and triggers the outgrowth of any spores. The second boiling kills the outgrown spores as they are now vegetative cells and the third boiling is for good measure. There is a third method we used in some labs; throw them into the coal-fired boiler. Any bacteria that survived the fire and 100ft chimney was welcome to freedom.

Micro-waving incubated plated WILL NOT sterilize them; if you can't afford the proper equipment, don't allow the experiment!

Cheers,
Tim Bloomer
Nth Bundaberg High

[Ocker]

Then there is the other methord I bagged them up last year and needed new rubber ring for pressure cooker, It took a couple of months to source new ring then pulled bag out of cupboard and every thing had dried right out. just finished pressure cooking this years lot.

[labman]

Hi Narelle,
I have a great slideshow, which has pictures of, and names, various growths on agar plates. I have tried to attach it, but unfortunately, the file is too big.
If you could provide me with an email address, (either p.m or on this forum) I would be happy to send it on. I'm sure you would find it useful.
Cheers,
Lisa

[Sassi]

Hi Lisa,

Could I please also have a copy, am just about to start growing things and I think it would help me and my new teachers as they are all a bit stressed with the workload here.

Many thanks,

Sass

Saberg@wenona.nsw.edu.au