I haven't heard of any white bacteria. If something is damp and warm I guess white mould could form but I've never had an issue even with a load of soggy bedding at the bottom of the cage! Paper bedding does breathe.
At some point, I was looking for ground corn cob as a medium, and ran across a post on justanswer.com, where the responder indicated that aspergillus fungus (condition known as aspergillosis) can result from damp shavings, esp corn cob, etc. Actually not a bacteria, but a fungus. Sounds real.