Are physarum eating bacteria on oats?

[Adam Strandberg]

Hi all,

I have been getting an increasing amount of mold on my plates and was wondering about ways to mitigate that. I assume one source could be the oats themselves, so I wanted to sterilize them. According to the Carolina guide to growing Physarum, though, the slime eats the bacteria on the oats, not the oats themselves. So I didn't bother trying. However, I just looked at the literature and this paper claims that autoclaving is fine. There is also this SliMoCo post that reports sterilizing the oats with ethanol.

Is Carolina just wrong about the food source? Has anyone tried growing physarum on just bacteria derived from the oats?

Planning on testing out autoclaving the oats (using my home Instant Pot) tonight or tomorrow, will update in the thread.

[ian]

Hi

When they're plasmodia they're definitely digesting the oats directly - you can see particles of oat in the endoplasm, starch grains are obvious in endocytotic vacuoles under EM and you just don't see enveloped bacteria. Cooked oats are consumed just as quickly and sterile oat agar is also happily eaten and in the lab I use oats loaded with dye that are definitely sterile yet you see ingestion within half an hour - not long enough for bugs to grow. 

I find sterilising oats just isn't worth the effort unless you have a specific problem ( which could be the source of oats - I've had some bad batches, or the temperature or the strain ( some just don't cope  ) - for general growth I've been using oats out of the bag, tap water and my hands for years now,  less than one in twenty trays goes down with anything - pin mould crops up after a few days but it certainly doesn't hassle the slimes and I've usually moved them to a new dish by then. 

[Adam Strandberg]

So it's normal to rotate dishes every couple days? When I got my original culture a couple months ago it took about a week for issues to start cropping up in a plate whereas now I'm getting pin mold within 24 hours

[ian]

Container rotation is important, old food is usually where problems start . I also wouldn't keep a culture on the go for more than a week or so - contamination builds up and starts getting transferred with slime. You can buy some time by making the slime crawl  long distance to a new food patch but by day seven mine are being dried down and fresh ones started. 

[Patrick Barry]

day seven?

the paper I'm looking at was growing slimes (on a 225mm square plate) didn't see consolidation until day 18 . The majority of the experiment runs they did failed due to mould contamination before that point.

Is this a matter of using a too large plate, so the network was not fully formed since the slime couldn't grow fast enough to cover it before the oats were really mouldy? 

[RyChu]

Not exactly sure what the situation is that you are describing, but I would suggest adding oats to the edges of the mold so they get covered quickly.