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Quote from wallaby:
Pat Rusin from the University of Arizona is not sure why the shared toilet seat, which you would expect to be a maelstrom of maximum microbial activity, is actually one of the cleanest. He said "What we found, and what we are still theorising as to why, is that the toilet seat was always the cleanest site." One theory is that the toilet seats are too dry to give a good home to a large population of bacteria.