Aussie
Its may not be contaminated fuel. I imagine that Jet Fuel may have some bug killing additives, but maybe not! Its been a long known problem, mainly in the marine environment where you get condensation in tanks.
When the H2O settles into a nice dark corner and not disturbed too often these little bugs have a very comfy home and breed faster than rabbits!
Diesel suffers far more than petrol and I would say Jet fuel also, as its not that much different!
Over time the water may be disturbed and the fungus has grown, then it gets killed off by the fuel, the fungud falls off the wall like a ... well a bit of a mushroom corossed with silicone, and makes a great fuel line and filter blocker. Albeit you need a lot of it. You would swear someone had gone mad with a silicone tube, but its not at all.
Now exactly what you get in the wing of an airliner, I can not say first hand but it would be quite likely its very similar.
J