A pair of contenders hoping to join the state symbol club would honor two equally famous Wisconsin traditions: cheese and Harley-Davidson motorcycles. One bill, introduced last week, aims to celebrate Lactococcus lactis, a tiny organism that makes the state’s estimated $18 billion per year cheese industry possible, by naming it the official state microbe. The other would designate Harley-Davidson the Wisconsin state motorcycle. The microbe already has a big fan base at UW-Madison, where bacteriologists have started pushing for the bill by creating a Web page that proclaims, “Support Lactococcus lactis as the Wisconsin State Microbe.”