Australia's Science Forum

That's ok Happens to the best of us!!

Sterilize swabs.
I put two cotton buds in small test tube. Stopper with cotton wool. Put them in a brown paper bag and "cook" them in the oven at 160 degrees for about an hour. Glass ware, for example test tubes or petri dishes can be treated same way.

Rosalie (another one)

Ocean Breeze,
I would not be BOILING the peppercorn broth, as that would kill the bacteria. Just leave it for a couple of days in room temp water and strain off the liquid.

Rosaliemb,
I don't have an oven to sterilise my cotton wool swabs. Do you think a Microwave would work? Any other ideas about how to sterilise the cotton wool swabs?

cheers
Ian

I don't bother sterilising cotton swabs, but I guess it should be done to avoid contamination. I've never witnessed cross contamination when trying to produce a lawn of a pure bacterium, however I also do have a UV Sterilisation cabinet that I use for forceps, scalpels, other dissecting equipment so that's what I might try from now on.

Jumping back to this peppercorn infusion, what antiseptics are good for killing it? I'm hoping to use it this week (Friday) for a prac. The kids test two different antiseptics on their plates. I think usually we do dettol and betadine. Would either/both of these kill the bacteria from the peppercorn?

Ian wrote:

mtg wrote:If the plates are taped around the edges after exposure and never untaped and then autoclaved, is the dreadful stuff grown from door handles etc ok? Will be trying peppercorns for biol but Yr8 microbes will probably still be looking at what grows from what and where!!!!

I think that it is not so much what might happen if everything is done correctly, that we need to worry about. Rather what might happen id something goes wrong. The "Wild Cultures" are OK if kept in sealed Petri Dishes until autoclaved, but what if somebody drops one and accidentally steps on it? or if some kid who knows no better opens it up? Something like Bacillus Subtilis is actually known to be BENEFICIAL to humans rather than harmful, and it can be effectively killed with household disinfectant. No need to autoclave!

Cheers
Ian

Hi Ian,
Just wondering where you got the info that Bacillus Subtilis is beneficial, not harmful? I've tried googling it and haven't found an answer!
Thanks,
Rosalie

So of course my next search came up with an answer... but now I need to prove that bacillus subtilis is actually what we are growing in the peppercorn infusion... do you know where I can find that info?

If you ring Kathy Morris at Miller Tech High, NSW she may be able to help you. The labbie that did all the research into this has retired, but Kathy I am sure would have all the information, they are good friends.

Google "Bacillus Subtilis is actually known to be BENEFICIAL" Wikipedia in safety section gives a little more detail. Not much though

Hi guys
My year 6 teachers want to do steve spanglers "growing Bacteria" experiment next term. http://www.chemtalk.com.au/viewtopic.php?f=26&t=451/lab ... g-bacteria
I am not really happy for them to do it. I know there is some discussion about whether these kinds of experiments should be allowed or not. Either way I think that year 6 with non-science trained staff is probably not a good idea. I think they think that I am being overly dramatic, "i mean it is on the internet and he did the experiment on a tv show!" It also says that you can just throw them in the bin afterwards! If I did all the things like not incubating above 30 degrees (it was 34 here yesterday!) taping them completely shut before they look at them, and safely disposing of them, would you think it was OK?
I did think of suggesting the peppercorn thing to them but I don't think that really shows what they want to show (ie how dirty door handles and keyboards are and how germs can multiply).
They are going to do one with bread in different environments to show mould growth but wanted another one to do.

Hi Nicky,

Can they do a before & after so have 1 pre grown plate, that you may be able to do for them, and have a clean plate, so they can see what it looks like first? Just a suggestion.
This is something they could give the kids a 'taste' of what they may be doing when they get to the Senior School, I dont mean taste the plates haha
I wouldnt be happy for them to grow their own plates either, and not to throw them in the bin WT, why do we have to go by the rules but when someone else wants to do it, rules are out the window (sorry now off loading LOL)

Lisa

The thing I would point out too is just because its ok to do something in the US doesn't mean its ok to do it here.

nickykinz wrote:If I did all the things like not incubating above 30 degrees (it was 34 here yesterday!) taping them completely shut before they look at them, and safely disposing of them, would you think it was OK?

WARNING: Never tape culture plates around the edges unless you use Parafilm. Sticky tape just will not suffice. Otherwise you may culture anaerobic bacteria, which must not be grown in schools, due to severe consequences should the seal be accidentally breached.

I'm leary of even using Parafilm except to seal in water when it's particularly dry, but given the temperatures hear in summer often rise into the 30's, I'm doublely disinclined to grow cultures then. It's also not safe to autoclave Parafilm, so it has to be removed before sterilisation.

Just tape the dishes together across the edge in three or four places to secure them firmly. This will allow air to difuse beween the join, as it needs to, but prevent spores from migrating.

Hey Graham,
I was wondering if you know why it's not safe to autoclave parafilm. I autoclave the diposable petri dishes, tape and all before I dispose of them in the garbage. Should I stop doing that?
regards,

Loopy wrote:Hey Graham,
I was wondering if you know why it's not safe to autoclave parafilm. I autoclave the diposable petri dishes, tape and all before I dispose of them in the garbage. Should I stop doing that?
regards,

It seems like I'm following you we use sticky tape over the top, into a oven bag then autoclave. Seems I'm learning something new every day.

In regards to taping them around the edges, I meant immediately before them looking at them, not while they are incubating. Just to stop silly ones getting them open too easily. I don't trust the Year 6's enough. They would be disposed of immediately after viewing.
Also, there has just been a discussion on Labbies about not using Parafilm to completely seal them, as it isn't clear if it is permeable and could still give rise to anaerobic bacteria.