In regards to your original question...any porous material has the potential to house more bacteria. So yes wood could hold more then say plastic which holds more then glass.

However...if you seal the wood then you won't be able to tell a difference. Also, if you practice good husbandry (ie. cleaning often, not letting waste sit, etc.) you shouldn't have any issues.

This is similar to the debate on if plastic cutting boards are so much better then wood ones...the jury is still out and there is no scientific proof (when taken care of) that one houses more than another.

The real question in not what to make it out of but what you want to do with it, and where you want to keep them.