A few minutes ago I had cleaned out a pot used for cheese sauce. When the time had come to clean the cheese residue off of the kitchen sponge, I noticed something strange; a thick layer of the residue would not come off. Upon closer inspection, I realized that the cheese appeared to have crystallized on the kitchen sponge. It doesn't seem to be a stretch to hypothesize that bacteria were responsible, although it is unusual that this happened to quickly. By what known mechanisms might a thing such as this happen?