What is the classification of Flood?

This has been a subject that has puzzled me for quite some time. Does anybody know what kind of organism the Flood is? I have searched all canonical data about their species and can’t find anything. Do you think it would be considered Bacteria due to the Flood Super Cell, or does it seem more like a fungal creature? Any insight, observations, or even guesses would be much appreciated.

I remember that the inspiration of design flood comes from fungus infected toes and rotten vegetables.

That’s pretty interesting information, I appreciate it!