Black beans looking like natto

[Guest guest]

I left a black bean salad in my refrigerator for about a week, and now

it has developed minute natto-like threads. I had some storebought

natto open in my refrigerator recently. Is it possible that the natto

spores lingered in my fridge and " contaminated " the black beans? Or

is this just what " spoiled " beans look like? I don't know, looks an

awful lot like natto!

I ate some of them and they taste fine.

Mark