On an episode, scienc in theme, the Discovery channel, many years ago, did a test of a wooden
cutting board and a plastic 'board'. Both were treated with the same food and left out overnight.
In the morning, they found that the wooden board had almost no bacteria in comparison with the plastic. The assumption was that wood contains natural bacteria-fighting little agents inherent in a healthy tree and which are naintained in the wood cut from it.
It was just a theory.