Unidentified yeast/bacteria

I posted this up in fermentation/yeast and after nearly a day with no responses decided it may be better here. Sorry for the double post, but here it is.

So recently I picked up an infection. Luckily it looks to be confined to only a single mason jar. However, said mason jar nearly blew its lid in the refrigerator. It was some saved WLP001 that I was keeping.

Since it smelled and tasted good I decided to keep it for later use. I poured it into a quart sized container and topped it up with apple juice and a touch of yeast nutrient. I then placed it in the fridge. The next day it's kicked up a krausen and is souring, this at about 44F. Anyone ever see a lacto strain capable of souring this quickly and vigorously at such a low temp?

I am new to sour brewing, but hopefully someone more knowledgeable will answer. My only advice is brew a small batch and see what happens, if it sours that fast, and is decent, rock it once and see!

What I hear you are saying is some sach yeast has infected your new sour beer strain?