Re: What organism would feed on the mold in my water bottle?

To begin, throw away the water bottle. What was growing in the bottle was 
mold, not bacteria and once established it is very difficult to eradicate. 
It is not impossible to rid the bottle of the mold but short of placing 
into a laboratory sterilizer (assuming the plastic could handle the heat) 
you cannot be sure it has been eliminated.

Biology of Microorganisms
Brock, 10th Ed.