Tagged: physarum polycephalum

Thursday, February 7th 2013

A lot has happened since my last entry on January 23rd.

Here’s the rundown:

The incubator we ordered finally arrived on January 25th, and we tested it out for about 20 minutes.

The petri dish we had left out in the science room with only non-nutrient agar as a test culture dried up and resembled a warped sheet of very thin plastic.

On January 28th, we began our sclerotia-making endeavour.  The first step to converting growing plasmodia into its dormant stage (sclerotia) was to put it on nutrient agar and incubate it.  We prepared 6 petri dishes with semi-defined (nutrient) agar, transferring small bits of growing plasmodia onto 4 of them, leaving one out, exposed to the air in the kitchen this time as a test (like we did with the non-nutrient agar), and saving one for future use (and as a test) in our supply cabinet at room temperature.  We exposed the test plate to the kitchen air this time instead of the science room air because we thought the air in the science room may have contributed to drying it out since that room is heated more.  However, the results were the same: the agar dried up and formed a thin sheet of brittle dehydrated agar.

After preparing the petri dishes with the nutrient agar, waiting for them to set-up, lining them with filter paper, transferring the growing plasmodia onto the filter paper, sealing them with electrical tape, labelling them, and covering them with foil (to keep the cultures dark) then re-labelling the foil, we warmed the incubator up and put the petri dishes in.

We left the incubator on all night at its lowest setting (which turned out to be around 26-28 degrees Celsius), then turned it off the next day, waiting to see if the filter paper would dry at room temperature as we read it was supposed to.

Sometime after 24 hours, we opened our incubated cultures and transferred the growing slime mould that was still on its filter paper into new petri dishes that didn’t have any agar in them.  We then put these back into the incubator.

On January 30th, we changed the oats in all of our growing cultures (the ones we were trying to make into sclerotia did not have oats) and looked at the original culture under a microscope.  It looked….yellow.

We also came up with a couple of drafts for a possible maze, and are planning to test our maze-making skills tomorrow when my partner brings in some lego.

On January 30th, our plan for making the maze was to build it on a base piece and stick it directly into a Tupperware container we had previously purchased at the dollar store.  But little did we know that on January 31st we would find out that the container featured an obvious yet hidden divider, making it unsuitable for out plan.  Dunn dunn dunn dunnnn….

As it tuns out, the packaging of the container had conveniently covered the part where your could see the divider, so, upon purchasing the container, we didn’t know it had one.  Therefore, the lego base piece didn’t fit into the container and we were left with another problem to solve.

We continued checking on the filter paper the next day or two to see if it was dry, but ended up finishing the sclerotia-making process shortly after we discovered another type of mould growing in one of the incubated cultures.  Though the filter paper was not completely dry, the slime mould had formed small, dry, crusty clusters that were slightly darker in colour to the growing mould.  We presumed these to be sclerotia.

We cut the filter paper that had the clusters and placed them in two other (plain) petri dishes – one for the transferred pieces that came from the contaminated culture and a separate one for the rest of them (prejudice, I know).  We proceeded to cover these in foil to keep them dark, and they have been sitting undisturbed in the supply cabinet since.

When we transferred the migrating plasmodia that was on the filter paper from nutrient agar to empty petri dishes, we kept the supposedly ‘mould-free’ plates of nutrient agar that we used.  Looking at them now, they are infested with other types of mould, and are quite interesting.  Is that what we’re breathing in the air all the time?  I guess those plates display the difference between non-nutrient and nutrient agar: one is easy to keep unwanted things from growing on (the non-nutrient agar) and the other is not.  Or so it would seem.

It is interesting to note that the petri dish of nutrient agar that we sealed immediately after preparing and have not re-opened since has not grown anything,  So how did the other mould get onto the now slime mould-free plates?  Some things might have to remain a mystery, but they didn’t just appear out of thin air …actually, on second thought, they might have.

On February 4th we attempted to sterilize a few things….first some used petri dishes, then the lego we would use for our maze,  We soon discovered that a) petri dishes cannot withstand boiling water and b) lego doesn’t do much better.  After first trying the petri dishes and ending up with warped tree ornaments, we thought we would be smarter with the lego and try a test piece.  Unfortunately we discovered a little too late that the two-blocks could withstand boiling but the others could not.  Our lego blocks and base piece now not able to be attached together again, not to mention being slightly discoloured, we had to think up another plan of action.

Our new bright idea (let’s hope this one turns out better than the last one) was to get a Tupperware container’s undivided attention (or, rather, just a Tupperware container without any division at all), that would fit the size of the maze, put a layer of non-nutrient agar on the bottom, and stick the lego pieces directly into the agar when it was semi-solidified.  We then embarked on the now somewhat habitual task of melting and pouring the agar.

My partner took care of fixing the lego pieces into place with only minor complications.  The only things that went wrong were a) the agar solidified a little too much before the lego places were placed in it, resulting in small cracks, and b) there was a slight change in formation as far as the shape of the maze (apparently my drawing skills could use some improvement).

With a few re-calculations today (due to the slight change in shape of the maze) on how long the mould would take to solve the maze if it grew at top speed, we came up with an estimated time of maze completion being about 10.2 hours.  However, we are expecting the mould to take longer than that, as that is the top speed we read that slime mould grows (1.8 cm / hour), and another source said only 1 cm / hour.

One of us is planning to take the mould home while it is solving the maze so we know exactly how long it took to solve the maze.

Looking at our original culture we discovered a bit of contamination from some type of black mould.  We removed the chunk that was contaminated and soon discovered that our other cultures were growing out of their petri dishes.  Looks like the taping job we did didn’t quite suffice, and the mould must have been hungry because it was making it’s way down the sides of the petri dishes, probably looking for food.   We washed the lids of the petri dishes, cleaned up the sides and bottoms of the containers, and re-taped them – better than last time.  We also changed the oat flakes that the cultures were eating, giving them fresh ones and trying to put them in the centre this time to encourage the slime mould to grow into the middle of the petri dishes rather than toward the outside.

I think that about sums it up!  Tomorrow we put some mould in the maze and see how it goes!


Friday, January 18th 2013

The slime mould kit we ordered arrived on Wednesday afternoon, but we are sill awaiting the incubator and other supplies.  The mould will be left in the fridge for the weekend, and hopefully on Monday the incubator will arrive and we can start growing the mould.  Once the culture is large enough, we hope to subculture it, and that way if one plate dies or becomes contaminated, we’ll still have some to work with.  First we’re going to experiment with growing the mould, keeping it alive, sub-culturing it, and transferring it to and from its dormant stage.  Then we’re going to try to work out how to set up the maze so we can test how long it takes to get through it.

Monday, December 17th 2012

On Sunday my partner and I went hunting in the forest for slime mould.  First we found some fungus we thought was slime mould, but when we took it home to examine we found out it was actually some kind of orange jelly fungus.  We went hunting again and brought back a few more samples, though non of them appear to be the illusive slime physarum polycephalum.  They may be part of the family of slime moulds, but are not what we need for our experiment.  Today we looked at the samples we brought back under a microscope (during inquiry time).