Are these filaments on my plated colony pseudohyphae or a contaminant?

[tkw954]

Here are some pics of my first attempt at culturing a yeast from a commercial bottle of Blanche de Chambly. I dumped the dregs into some hopped wort I had canned and put it on a stir-plate for a few days. I then used a innoculation loop to streak a plate of unhopped wort agar. I got some nice single colonies but there appeared to be some contaminants on the plate, so I picked one colony and transferred it to a new plate. That colony is what's shown in the pictures.

At first, I thought I'd transferred something else along with the yeast colony, as it's grown tendrils that look a lot like fungal mycelium. (I took a second colony and it shows the same.)

However, a brewer on Reddit pointed out that some yeast can transform to a mycelium form, and further research revealed that certain yeast, when starved of nitrogen, from filaments called pseudohyphae that can gather nutrients from farther away. It's stated that this ability is rare in commercial yeast, but since Unibroue's yeast is somewhat funky anyway, this might be an explanation for the filaments growing from my colony.

I can't find any non-microscopic pictures of what these pseudohyphae looks like. Can anyone confirm or deny that's what I'm growing?

Thanks.

References (probably paywalled):
"Unipolar cell divisions in the yeast S. cerevisiae lead to filamentous growth: Regulation by starvation and RAS"

"Filamentous growth in budding yeast"

 

[ColoHox]

If only particular colonies were showing this filamentous growth, I would guess that you don't have a nitrogen deficiency, and instead probably have a contaminant. What was the distribution of colony types between "normal" and "filamentous?"

Brettanomyces is more likely to have filamentous growth than Saccharomyces. On the surface, these two cultures will be very similar. You do raise a good point, in that Unibroue may be using a mutated strain, but I would expect most of the cultures to have this appearance then.

 

[tkw954]

The original streak plate was covered with these tendrils, but I didn't notice because of poor visibility (you can only really see them if you hold the plate up to the light) and because I thought it was just a surface texture of the agar. So it's hard to judge prevalence from the original streak plate.

I replated two colonies from the streak, and both show the same filaments radiating from the colony.

 

[deeringbrewing]

I would say contamination.

 

[tkw954]

Yup, it turned black and sprouted something like pin-mould. Into the pressure cooker!